How to pass data between the View and the ViewModel

How to pass data between the View and the ViewModel - c#

I'm a newbie in the MVVM design patter I'm trying to create a simple app where a list of students is shown in the main window and I want the user to be able to add a new student to the list I have accomplished the binding of the observable collection where the students' data are but how can I create a new user by fetching the data from the textboxes and using them as a parameter in a command
Here is my View
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="2*"/>
<RowDefinition Height="2*"/>
<RowDefinition Height="2*"/>
<RowDefinition Height="*"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<TextBlock x:Name="NameTextBlock"
Text="Name"
Style="{StaticResource TextBlockTextStyle}"/>
<TextBlock x:Name="SurnameTextBlock"
Grid.Row="1"
Text="Surname"
Style="{StaticResource TextBlockTextStyle}"/>
<TextBlock x:Name="AgeTextBlock"
Grid.Row="2"
Text="Age"
Style="{StaticResource TextBlockTextStyle}"/>
<TextBox x:Name="NameTextBox"
Grid.Column="1"
Style="{StaticResource TextBoxTextStyle}"/>
<TextBox x:Name="SurnameTextBox"
Grid.Row="1"
Grid.Column="1"
Style="{StaticResource TextBoxTextStyle}"/>
<TextBox x:Name="AgeTextBox"
Grid.Row="2"
Grid.Column="1"
Style="{StaticResource TextBoxTextStyle}"/>
<ListBox x:Name="StudentListBox"
Grid.ColumnSpan="2"
Grid.Row="4"
Style="{StaticResource ListBoxStyle}"
ItemsSource="{Binding StudentList}">
<ListBox.ItemTemplate>
<DataTemplate>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<TextBlock Text="{Binding Name}"
Style="{StaticResource TextBlockTextStyle}"/>
<TextBlock Text="{Binding Surname}"
Grid.Column="1"
Style="{StaticResource TextBlockTextStyle}"/>
<TextBlock Text="{Binding Age}"
Grid.Column="2"
Style="{StaticResource TextBlockTextStyle}"/>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
<Button x:Name="AddButton"
Grid.Row="7"
Grid.ColumnSpan="2"
HorizontalAlignment="Center"
Content="Add"
Margin="7,7,7,7"
Command="{Binding AddStudentCommand}"/>
</Grid>
And here is my ViewModel
public class MainViewModel : ViewModelBase
{
ObservableCollection<Student> studentList;
public MainViewModel()
{
//populate some sample data
studentList = new ObservableCollection<Student>()
{
new Student(){Name="John", Surname="Smith", Age="28"},
new Student(){Name="Barbara", Surname="Anderson", Age="23"}
};
}
public ObservableCollection<Student> StudentList
{
get { return studentList; }
set { RaisePropertyChanged("studentList"); }
}
Student selectedPerson;
public Student SelectedPerson
{
get { return selectedPerson; }
set
{
selectedPerson = value;
RaisePropertyChanged("SelectedPerson");
}
}
private RelayCommand _addStudentCommand;
public ICommand AddStudentCommand
{
get
{
return _addStudentCommand
?? (_addStudentCommand = new RelayCommand(() =>
{
Student student = new Student();
// here should be the logic of defining the name, surname,
// age and id of the newly created student
studentList.Add(student);
}));
}
}
}
I am using MVVMLight in the current project and there are a lot of thing that I do not understand so please explain how I should pass the data of the textboxes and what exactly should happen in the command that it is being used.
Tell me to add more of the code if necessary.

What I would do is create some properties that the textboxes are bound to in the ViewModel.
Like this for all three (in your viewmodel)
private string _Name;
public string Name
{
get { return _Name; }
set
{
_Name = value;
RaisePropertyChanged("Name");
}
}
Then, in the XAML, bind the textbox's text to this:
<TextBox x:Name="NameTextBox"
Text="{Binding Name}"
Grid.Column="1"
/>
Finally in the AddStudent Command you reference the properties in the viewmodel that are bound to the textboxes.
private RelayCommand _addStudentCommand;
public ICommand AddStudentCommand
{
get
{
return _addStudentCommand
?? (_addStudentCommand = new RelayCommand(() =>
{
Student student = new Student();
student.Name = this.Name;
student.Surname = this.Surname;
student.Age = this.Age;
// here should be the logic of defining the name, surname,
// age and id of the newly created student
_StudentList.Add(student);
}));
}
}

(cheekily posted from my comment)
As you've stated, you've not had much experience and don't understand much with MVVM, so although I could answer this question, I think the best thing I could do is provide you with a few links to watch :
youtube.com/watch?v=BClf7GZR0DQ
and
channel9.msdn.com/blogs/kreekman/
The second video is from the guy who wrote MVVM-light.
They basically cover the same material, but both bring a slightly different perspective!

Related

Editing copies of an ObservableCollection's Object without editing the ObservableCollection

I have a WPF form that I want to use to manipulate a database table. To get the data out of the database I use Entity Framework Core. I try to follow the MVVM pattern.
So I have a Model called Employee with a number of string properties like Firstname and so on.
The form has a ListView that shows an ObservableCollection of Employee. Further I have a number of TextBoxes to display and manipulate the properties of single Employee objects. The selectedMemberPath of the ListView is bound to a property SelectedEmployee. The setter of SelectedEmployee than copies it's own properties to EditedEmployee. The TextBoxes are bound to EditedEmployee. The idea is, that I don't want to directly edit the ObservableCollection. This should only happen if a save button is clicked.
This is my view model.
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.ChangeTracking;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using XdcCore.Models;
using XdcCore.ViewModels.Commands;
namespace XdcCore.ViewModels
{
class EmployeeEditorVM : List<Employee>, INotifyPropertyChanged
{
public EmployeeSaveCommand EmployeeSaveCommand { get; set; }
public EmployeeEditorVM()
{
EmployeeSearch();
EmployeeSaveCommand = new EmployeeSaveCommand(this);
}
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
private string employeeSearchText;
public string EmployeeSearchText
{
get { return employeeSearchText; }
set
{
employeeSearchText = value;
OnPropertyChanged("EmployeeSearch");
EmployeeSearch();
}
}
private Employee selectedEmployee;
public Employee SelectedEmployee
{
get { return selectedEmployee; }
set
{
selectedEmployee = value;
OnPropertyChanged("SelectedEmployee");
EditedEmployee = SelectedEmployee;
}
}
private Employee editedEmployee;
public Employee EditedEmployee
{
get { return editedEmployee; }
set
{
editedEmployee = value;
OnPropertyChanged("EditedEmployee");
}
}
private ObservableCollection<Employee> employees;
public ObservableCollection<Employee> Employees
{
get { return employees; }
set
{
employees = value;
OnPropertyChanged("Employees");
}
}
public void EmployeeSearch()
{
using (var context = new XdcContext())
{
if (employeeSearchText != null)
{
var _employees = context.Employee
.Where(x => x.Firstname.Contains(employeeSearchText));
Employees = new ObservableCollection<Employee>(_employees);
}
else
{
var _employees = context.Employee.Select(x => x);
Employees = new ObservableCollection<Employee>(_employees);
}
}
}
public void EmployeeSave()
{
using (var context = new XdcContext())
{
var entity = context.Employee.First(x => x.IdEmployee == SelectedEmployee.IdEmployee);
{
entity.Firstname = SelectedEmployee.Firstname;
entity.Lastname = SelectedEmployee.Lastname;
entity.Initials = SelectedEmployee.Initials;
context.SaveChanges();
}
EmployeeSearch();
}
}
}
}
this is my View:
<Window
x:Class="XdcCore.Views.Editors.EmployeeEditor"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:XdcCore.Views.Editors"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:vm="clr-namespace:XdcCore.ViewModels"
Title="Employee"
Width="800"
Height="450"
mc:Ignorable="d">
<Window.Resources>
<vm:EmployeeEditorVM x:Key="vm" />
</Window.Resources>
<Grid DataContext="{StaticResource vm}">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="300" />
<ColumnDefinition Width="115*" />
<ColumnDefinition Width="277*" />
</Grid.ColumnDefinitions>
<!-- left column -->
<Border BorderBrush="DarkGray" BorderThickness="1">
<Grid Grid.Column="0">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
<RowDefinition Height="aUTO" />
</Grid.RowDefinitions>
<Label
Grid.Row="0"
Margin="3,3,3,3"
Content="Filter:" />
<TextBox
x:Name="TextBoxSearch"
Grid.Row="1"
Height="25"
Margin="3,0,3,3"
HorizontalContentAlignment="Left"
VerticalContentAlignment="Center"
Text="{Binding EmployeeSearchText, Mode=TwoWay}" />
<ListView
x:Name="ListViewOverview"
Grid.Row="2"
Margin="3,0,3,0"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
ItemsSource="{Binding Employees, Mode=OneWay}"
SelectedItem="{Binding SelectedEmployee, Mode=OneWayToSource}">
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Initials}" />
<TextBlock Text=" : " />
<TextBlock Text="{Binding Firstname}" />
<TextBlock Text=" " />
<TextBlock Text="{Binding Lastname}" />
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<Grid Grid.Row="3">
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Button
x:Name="ButtonDelete"
Grid.Column="0"
Height="25"
Margin="3,3,3,3"
Content="Delete"
IsEnabled="False" />
<Button
x:Name="ButtonNew"
Grid.Column="1"
Height="25"
Margin="3,3,3,3"
Content="Add New ..."
IsEnabled="True" />
</Grid>
</Grid>
</Border>
<!-- right Column -->
<Grid Grid.Column="1" Grid.ColumnSpan="2">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<!-- right column, first row -->
<Border
Grid.Row="0"
BorderBrush="DarkGray"
BorderThickness="1">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="25" />
<RowDefinition Height="25" />
<RowDefinition Height="25" />
<RowDefinition Height="25" />
<RowDefinition Height="25" />
<RowDefinition Height="25" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="100" />
<ColumnDefinition Width="200" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Label
Grid.Row="0"
Grid.Column="0"
HorizontalAlignment="Right"
Content="First Name" />
<Label
Grid.Row="1"
Grid.Column="0"
HorizontalAlignment="Right"
Content="Last Name" />
<Label
Grid.Row="2"
Grid.Column="0"
HorizontalAlignment="Right"
Content="Initials" />
<Label
Grid.Row="3"
Grid.Column="0"
HorizontalAlignment="Right"
VerticalContentAlignment="Center"
Content="ID" />
<Label
Grid.Row="4"
Grid.Column="0"
HorizontalAlignment="Right"
VerticalContentAlignment="Center"
Content="RCU" />
<Label
Grid.Row="5"
Grid.Column="0"
HorizontalAlignment="Right"
VerticalContentAlignment="Center"
Content="RCT" />
<TextBox
x:Name="TextBoxFirstName"
Grid.Row="0"
Grid.Column="1"
Margin="0,3,3,3"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
HorizontalContentAlignment="Left"
VerticalContentAlignment="Center"
Text="{Binding EditedEmployee.Firstname, Mode=TwoWay}" />
<TextBox
x:Name="TextBoxLastName"
Grid.Row="1"
Grid.Column="1"
Margin="0,3,3,3"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
HorizontalContentAlignment="Left"
VerticalContentAlignment="Center"
Text="{Binding EditedEmployee.Lastname, Mode=TwoWay}" />
<TextBox
x:Name="TextBoxInitials"
Grid.Row="2"
Grid.Column="1"
Margin="0,3,3,3"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
HorizontalContentAlignment="Left"
VerticalContentAlignment="Center"
Text="{Binding EditedEmployee.Initials, Mode=TwoWay}" />
<TextBox
x:Name="TextBoxId"
Grid.Row="3"
Grid.Column="1"
Margin="0,3,3,3"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
HorizontalContentAlignment="Left"
VerticalContentAlignment="Center"
IsReadOnly="True" />
<TextBox
x:Name="TextBoxRCU"
Grid.Row="4"
Grid.Column="1"
Margin="0,3,3,3"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
HorizontalContentAlignment="Left"
VerticalContentAlignment="Center"
IsReadOnly="True" />
<TextBox
x:Name="TextBoxRCT"
Grid.Row="5"
Grid.Column="1"
Margin="0,3,3,3"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
HorizontalContentAlignment="Left"
VerticalContentAlignment="Center"
IsReadOnly="True" />
</Grid>
</Border>
<Grid Grid.Row="1">
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Button
x:Name="ButnSave"
Grid.Column="1"
Width="76"
Height="25"
Margin="60,3,60,0"
HorizontalAlignment="Center"
VerticalAlignment="Top"
Command="{Binding EmployeeSaveCommand}"
Content="Save"
IsEnabled="True" />
</Grid>
<!-- Add new -->
</Grid>
</Grid>
</Grid>
</Window>
In other words: I want to click on an item in the list view, it's details are shown in the text boxes. I can change the text in the text boxes but the changes are not applied to the observable collection (or even database) until I click "save". The problem is, that exactly that happens: when I edit text in the text boxes the changes are also shown in the list view. And I can#t see why.

So, I got the concept of "copy vs point" of a variable wrong.
I had two solutions for my problem.
To my Employee model I added the method Copy:
public partial class Employee
{
public int IdEmployee { get; set; }
public string Initials { get; set; }
public string Firstname { get; set; }
public string Lastname { get; set; }
public string Rcu { get; set; }
public DateTime Rct { get; set; }
public Employee Copy()
{
return (Employee)this.MemberwiseClone();
}
}
Then I Changed my ViewModel so that EditedEmployee is a copy of SelectedEmployee
private Employee selectedEmployee;
public Employee SelectedEmployee
{
get { return selectedEmployee; }
set
{
selectedEmployee = value;
OnPropertyChanged("SelectedEmployee");
if (SelectedEmployee != null)
{
EditedEmployee = SelectedEmployee.Copy();
}
}
}
private Employee editedEmployee;
public Employee EditedEmployee
{
get { return editedEmployee; }
set
{
editedEmployee = value;
OnPropertyChanged("EditedEmployee");
}
}
The problem with this approach is, that if I mess around with the database and then need to run Scaffold-DbContext (I prefer the code-first approach of EFC) again, I would have to modify all models again. A solution to that might be some a second, modified Model that inherits from the original Model and then adds the Copy method.
My second approach is to bind the ListView via SelectedIndex instead of SelectedItem.
<ListView
...
ItemsSource="{Binding Employees, Mode=OneWay}"
SelectedIndex="{Binding SelectedItemIndex, Mode=TwoWay}">
In the ViewModel this is then represented by an int property. If this int is set (and >= 0) Employee gets copied EmployeeWorkingCopy. Furthermore if EmployeeWorkingCopy is set a single Employee dubbed EditedEmployee is set as the Employee of the working copy with the selected index.
private int selectedItemIndex;
public int SelectedItemIndex
{
get { return selectedItemIndex; }
set
{
selectedItemIndex = value;
if (SelectedItemIndex >= 0)
EmployeesWorkingCopy = new ObservableCollection<Employee>(Employees);
}
}
private Employee editedEmployee;
public Employee EditedEmployee
{
get { return editedEmployee; }
set
{
editedEmployee = value;
OnPropertyChanged("EditedEmployee");
}
}
private ObservableCollection<Employee> employeesWorkingCopy;
public ObservableCollection<Employee> EmployeesWorkingCopy
{
get { return employeesWorkingCopy; }
set
{
employeesWorkingCopy = value;
EditedEmployee = EmployeesWorkingCopy[SelectedItemIndex];
}
}
Thanks a lot for pointing out my misconception.

How to have a custom display in ListBox with DataTemplate?

I need to display cards in a ListBox in a specific layout:
https://imgur.com/a/0U8eqTc
I've tried to find a way to use 2 types of DataTemplate but I have no idea how to do it. I decided to make a template which contains 6 card Template (like this):
https://imgur.com/VrOlYcR
Here's what my current Template looks like:
<ControlTemplate x:Key = "CardTemplate" TargetType = "Button">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="4*"/>
<RowDefinition Height="1*"/>
</Grid.RowDefinitions>
<Image Grid.Row="0" Source="{Binding Path=Image}"/>
<TextBlock Grid.Row="1" Text="{Binding Path=Titre}"/>
</Grid>
</ControlTemplate>
<DataTemplate x:Key="DataTemplate">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="1*"/>
<RowDefinition Height="1*"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1*"/>
<ColumnDefinition Width="1*"/>
</Grid.ColumnDefinitions>
<Button Grid.Column="0" Grid.Row="0" Template="{StaticResource CardTemplate}"/>
<Grid Grid.Column="1" Grid.Row="0">
<Grid.RowDefinitions>
<RowDefinition Height="1*"/>
<RowDefinition Height="1*"/>
</Grid.RowDefinitions>
<Button Grid.Row="0" Template="{StaticResource CardTemplate}"/>
<Button Grid.Row="1" Template="{StaticResource CardTemplate}"/>
</Grid>
<Grid Grid.Column="0" Grid.Row="1">
<Grid.RowDefinitions>
<RowDefinition Height="1*"/>
<RowDefinition Height="1*"/>
</Grid.RowDefinitions>
<Button Grid.Row="0" Template="{StaticResource CardTemplate}"/>
<Button Grid.Row="1" Template="{StaticResource CardTemplate}"/>
</Grid>
<Button Grid.Column="1" Grid.Row="1" Template="{StaticResource CardTemplate}"/>
</Grid>
</DataTemplate>
Which I intend to display in a ListBox:
<ListBox ScrollViewer.HorizontalScrollBarVisibility="Disabled"
Name="ListBox" ItemTemplate="{DynamicResource DataTemplate}"
ScrollBar.Scroll="ScrollOnBottom">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel/>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
</ListBox>
Here's how my cod behind basically works:
class Cards
{
public List<Card> cards; // list of 6 Card objects
}
class Card
{
string title;
BitmapImage image;
public string Title { get => title; set => title = value; }
public BitmapImage Image { get => image; set => image = value; }
}
ObservableCollection<Cards> cc = new ObservableCollection<Cards>();
/*
Cards are already filled with 6 Card
cc filled with Cards
*/
formationListBox.ItemsSource = cc;
Here's the problem, it displays the right amount of Cards but the buttons are empty. I don't know how to bind a specific object to each button.

To Give an example of what Sinatr commented. You should approach this from an Mvvm perspective. first you should add a View Model for the View that this Window is in. This will contain a list of objects that are DisplayCards each object will store the string and image.
public class DisplayCard : INotifyPropertyChanged
{
private string _title;
public string Title
{
get { return _title; }
set
{
if (value != _title) { _title = value; RaisePropertyChanged(); }
}
}
private string _cardImage;
public string CardImage
{
get { return _cardImage; }
set
{
if (value != _cardImage) { _cardImage = value; RaisePropertyChanged(); }
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged([CallerMemberName] string propertyName = "")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
public class YourViewVM : INotifyPropertyChanged
{
private ObservableCollection<DisplayCard> _cardCollection;
public ObservableCollection<DisplayCard> CardCollection
{
get { return _cardCollection; }
set
{
if (value != _cardCollection) { _cardCollection = value; RaisePropertyChanged(); }
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged([CallerMemberName] string propertyName = "")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
Then you need to make the list CardCollection set to the ListBox's ItemSource. Then use a datatemplate to bind the DisplayCards properties to the containing object.
<ListBox Name="lbTodoList" HorizontalContentAlignment="Stretch" ItemSource="{Binding CardCollection}">
<ListBox.ItemTemplate>
<DataTemplate>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="4*"/>
<RowDefinition Height="1*"/>
</Grid.RowDefinitions>
<Image Grid.Row="0" Source="{Binding Image}"/>
<TextBlock Grid.Row="1" Text="{Binding Title}"/>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
You need to make sure you set the YourViewVM As the DataContext of the View. A simple search should solve how to do that.
The above should be enough to allow you to refactor your code such that it works.

ObservableCollection not updated to UI when property changed

Question: ObservableCollection not updated to UI when property changed
What I have tried:
XAML view:
<UserControl x:Class="FlexilineDotNetGui.Flexiline.UserControls.UCRealestate"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
xmlns:translations="clr-namespace:FlexilineDotNetGui.Flexiline.Translations"
xmlns:viewModels="clr-namespace:FlexilineDotNetGui.Flexiline.ViewModels"
x:Name="Realestate"
DataContext="{StaticResource vmRealestate}">
<Grid Margin="5">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Grid Grid.Row="0" >
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<DataGrid Grid.Row="0" Grid.RowSpan="3" Grid.Column="0" Height="200" Margin="5"
ItemsSource="{Binding Panden, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" AutoGenerateColumns="False"
CanUserAddRows="False" IsReadOnly="True" SelectedItem="{Binding Pand}">
<DataGrid.Columns>
<DataGridTextColumn Header="{x:Static translations:UCRealestate.RegistrationType}" Binding="{Binding RegistrationType, Mode=TwoWay}" Width="Auto"/>
</DataGrid.Columns>
</DataGrid>
<Button Grid.Column="1" Grid.Row="0" Background="Transparent"
Width="20" Height="20" Padding="0" Margin="5" Command="{Binding AddPandCMD}"
CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type viewModels:RealestateViewModel}}}">
<Image Source="/Flexiline;component/Resources/New_16x16.ico"/>
</Button>
<Button Grid.Row="1" Grid.Column="1" VerticalAlignment="Top"
Width="20" Height="20" Padding="0" Background="Transparent" Margin="5" Command="{Binding DeletePandCMD}"
CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type viewModels:RealestateViewModel}}}">
<Image Source="/Flexiline;component/Resources/Delete_16x16.ico"/>
</Button>
<Grid Grid.Row="3" Margin="5">
<Grid>
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid Grid.Row="1" Grid.Column="1" Margin="0,5">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" MaxWidth="100"/>
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
</Grid>
<Label Grid.Row="2" Grid.Column="2" Content="{x:Static translations:UCRealestate.RegistrationType}" HorizontalContentAlignment="Right" VerticalAlignment="Center"/>
<ComboBox Grid.Row="2" Grid.Column="3" Margin="5" ItemsSource="{Binding AardInschrijving, UpdateSourceTrigger=PropertyChanged}" SelectedValue="{Binding SelectedAardInschrijving, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" DisplayMemberPath="Description" SelectedValuePath="FlexKey"/>
</Grid>
</Grid>
</Grid>
</Grid>
</Grid>
</UserControl>
ViewModel :
using FlexilineDotNet.SharedDomainLogic.Models.CommunicationModels;
using FlexilineDotNetGui.Domain.Controls;
using FlexilineDotNetGui.Domain.Models;
using GalaSoft.MvvmLight.Command;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Windows;
using System.Windows.Data;
namespace FlexilineDotNetGui.Flexiline.ViewModels
{
public class RealestateViewModel : ANavigationPaneSubViewModel, INotifyPropertyChanged
{
BorgRealestate _borgRealestate = new BorgRealestate();
ObservableCollection<BorgRealestate> ocPanden = new ObservableCollection<BorgRealestate>();
private DomainController _controller = DomainController.GetInstance();
public RelayCommand<object> AddPandCMD { get; private set; }
public RelayCommand<object> DeletePandCMD { get; private set; }
#region "properties"
public ObservableCollection<BorgRealestate> Panden
{
get
{
return ocPanden ?? (ocPanden = new ObservableCollection<BorgRealestate>());
}
set
{
if (ocPanden == value)
return;
ocPanden = value;
OnPropertyChanged("Panden");
}
}
//public ObservableCollection<BorgRealestate> Panden { get; }
public BorgRealestate Pand
{
get
{
return _borgRealestate ?? (_borgRealestate = new BorgRealestate());
}
set
{
if (value == _borgRealestate) return;
_borgRealestate = value;
OnPropertyChanged();
OnPropertyChanged("Panden");
}
}
public List<DropDownItem> AardInschrijving { get { return _controller.GetDropDownItemsByType("AardInschrijving"); } }
private DropDownItem SelectedAardInschrijvingDI
{
get
{
DropDownItem test = _controller.GetDropDownItemsByType("AardInschrijving").FirstOrDefault(x => x.FlexKey == _borgRealestate?.RegistrationType);
if (test == null)
{
test = _controller.GetDropDownItemsByType("AardInschrijving").FirstOrDefault();
}
return test;
}
set
{
OnPropertyChanged();
OnPropertyChanged("Panden");
}
}
public int SelectedAardInschrijving
{
get
{
return SelectedAardInschrijvingDI.FlexKey;
}
set
{
if (value == Pand?.RegistrationType) return;
Pand.RegistrationType = value;
OnPropertyChanged();
OnPropertyChanged("Panden");
}
}
public string SelectedAardInschrijvingText
{
get
{
return SelectedAardInschrijvingDI.Description;
}
}
#endregion
#region "ctor"
public RealestateViewModel()
{
//Panden = new ObservableCollection<BorgRealestate>();
AddPandCMD = new RelayCommand<object>(o => AddPand());
DeletePandCMD = new RelayCommand<object>(o => DeletePand());
}
#endregion
#region "methods"
private void AddPand()
{
BorgRealestate newBorgRealestate = new BorgRealestate { RegistrationType = SelectedAardInschrijving };
Panden.Add(newBorgRealestate);
}
private void DeletePand()
{
Panden.Remove(Pand);
}
#endregion
}
}
Problem description:
When I Update the combobox value, it's updated in the "Panden" property when I check with a breakpoint but the datagrid in the view is not updated. The problem exists with Oneway and also with TwoWay as I defined in datagrid columns. I have both modes tried.
The views are inside a dxnavbar control, when I switch between navbar items and back then the view is updated OK.
EDIT:
When the application starts, the Panden list is indeed null, I had forgotten to mention something....
In my view there is a datagrid with a button where I add items to the observable collection where also some of the properies as example nature inscription combobox value is shown in datagrid. This button is then connected to a relay command. That is the collection that i have binded to the datagridview.
the getter of the property property is not empty and is therefore filled with the correct values, only the changes do not change in the view.
it is indeed normal that the collection is null if no "Pand" items are added to the "Panden" collection via the provided button on the UI (relaycommand). But the "Pand" item in de datagrid will not update after i change a value from the combobox after adding an item with the button to the collection.
EDIT 21/11 08:54
This is the logic for adding the pand:
private void AddPand()
{
BorgRealestate newBorgRealestate = new BorgRealestate { RegistrationType = SelectedAardInschrijving };
Panden.Add(newBorgRealestate);
}
But after i add i see the items gets added to the collection and get also updated in the collection after the combobox value changed only not in ui. (when the row in the datagrid have the focus)

In this code here:
public ObservableCollection<BorgRealestate> Panden
{
get
{
return ocPanden ?? (ocPanden = new ObservableCollection<BorgRealestate>());
}
You create a new collection but you don't at that point call OnPropertyChanged; and you shouldn't because it would be wrong to do this here. Therefore, the UI doesn't know you've created the new collection. It looks like the first time the above getter is called is in your AddPand function. Therefore, the UI never receives an OnPropertyChanged for Panden and so does not update.
Instead of this create the collection in your constructor and you should find it will update. Also you may not need a setter at all for Panden if it is never recreated.
in constructor:
Panden = new ObservableCollection<BorgRealestate>();
Then Panden property becomes:
public ObservableCollection<BorgRealestate> Panden { get; }
Which can be simplified to:
public ObservableCollection<BorgRealestate> Panden { get; } = new ObservableCollection<BorgRealestate>();

In the Viewmodel:
That short piece of code did the trick:
CollectionViewSource.GetDefaultView(ocPanden).Refresh();
Replace this:
public ObservableCollection<BorgRealestate> Panden
{
get
{
return ocPanden ?? (ocPanden = new ObservableCollection<BorgRealestate>());
}
set
{
if (ocPanden == value)
return;
ocPanden = value;
OnPropertyChanged("Panden");
}
}
With this:
public ObservableCollection<BorgRealestate> Panden
{
get
{
if(ocPanden != null)
{
CollectionViewSource.GetDefaultView(ocPanden).Refresh(); //This will do the trick
}
return ocPanden ?? (ocPanden = new ObservableCollection<BorgRealestate>());
}
set
{
if (ocPanden == value)
return;
ocPanden = value;
OnPropertyChanged("Panden");
}
}
Unfortunately I have not yet found out where the cause really comes from?
If someone can know that then leave a message?

Binding a list of object to grid

Trying to render a ListView with a grid into it. The grid contains two columns. The first one, with a button. The second one, with a Label.
Model contains two attributes. First one, a List of specific object. Second one, a string.
Finally, the label of the grid inside of listview will be binded to the one random attribute of list of object of the Model.
My best approach is:
<ListView x:Name="intervectionList"
ItemsSource="{Binding .}">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<Grid Padding="5">
<Grid.RowDefinitions>
<RowDefinition Height="20"></RowDefinition>
<RowDefinition Height="1"></RowDefinition>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1*"></ColumnDefinition>
<ColumnDefinition Width="3*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<Button Text="Play" Grid.Row="0" Grid.Column="0" Clicked="OnLogginClicked"/>
<Label Grid.Row="0" Grid.Column="1" Text="{Binding random_attribute}"/>
<BoxView Color="Navy" HeightRequest="1" Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="2"/>
</Grid>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
CODE-BEHIND:
public Intervection()
{
InitializeComponent();
var obj= new Model();
this.BindingContext = prueba.List_of_object;
}
public class ViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void RaiseOnPropertyChange([CallerMemberName] string propertyName = null)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public ViewModel()
{
_viewmodel = new ViewModel();
}
private ViewModel _viewmodel;
private string _attribute1;
public string Attribute1
{
get { return _attribute1; }
set { _attribute1= value; RaiseOnPropertyChange(); }
}
.............
}
public class Model
{
public List<obj> Intervencion;
public string attribute2;
// Helpers...
}
That is not rendering anything.
I tried successive approaches. Coming from Basic ListView with string, ListView of object,... and so on. The problem is coming from when I insert the grid.
After check Stackoverflow. I found this link Create Grid from Code-Behind, but this is not serving to my purpose because I can´t re-write the view model. (I, even, tried to coded it).
As usual, thanks mates.

I have added the VerticalOptions to the Listview and Grid.
I have created a viewmodel in which I have one property, the list of items.
The viewmodel also implements INotifyPropertyChanged.
You can read about INotifyPropertyChanged here.
The INotifyPropertyChanged interface is used to notify clients,
typically binding clients, that a property value has changed.
XAML :
<ListView ItemsSource="{Binding MyObservableCollection}" VerticalOptions="FillAndExpand">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<Grid Padding="5" VerticalOptions="Fill">
<Grid.RowDefinitions>
<RowDefinition Height="20"></RowDefinition>
<RowDefinition Height="1"></RowDefinition>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1*"></ColumnDefinition>
<ColumnDefinition Width="3*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<Button Text="Play" Grid.Row="0" Grid.Column="0"/>
<Label Grid.Row="0" Grid.Column="1" Text="{Binding .}"/>
<BoxView Color="Navy" HeightRequest="1" Grid.Row="1"
Grid.Column="0" Grid.ColumnSpan="2"/>
</Grid>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
ViewModel :
public class ListViewWithGridViewModel : INotifyPropertyChanged
{
private ObservableCollection<string> _myObservableCollection;
public ListViewWithGridViewModel()
{
MyObservableCollection = new ObservableCollection<string>(new List<string> { "abc", "xyz", "pqr", "aaa", "abc", "xyz", "pqr", "aaa", "abc", "xyz", "pqr", "aaa" });
}
public ObservableCollection<string> MyObservableCollection
{
get { return _myObservableCollection; }
set
{
_myObservableCollection = value;
OnPropertyChanged();
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null) => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
XAML.cs :
public partial class ListViewWithGrid : ContentPage
{
public ListViewWithGrid()
{
InitializeComponent();
BindingContext = new ListViewWithGridViewModel();
}
}

Finally I got it. The xaml needed for it is the next one (you can complet all code coming from the code´s question). Posted just in case you all want to use another approach. Proper answer (more elegant) is #Rohit´s answer.
<ContentPage.Resources>
<ResourceDictionary>
<Color x:FactoryMethod="FromHex" x:Key="fondoBlancoPalido">
<x:Arguments>
<x:String>#F2F2F2</x:String>
</x:Arguments>
</Color>
</ResourceDictionary>
</ContentPage.Resources>
<ListView x:Name="listView" ItemsSource="{Binding .}" BackgroundColor="{StaticResource fondoBlancoPalido}">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<ViewCell.View>
<Grid Padding="5">
<Grid.RowDefinitions>
<RowDefinition Height="60"></RowDefinition>
<RowDefinition Height="60"></RowDefinition>
<RowDefinition Height="10"></RowDefinition>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1*"></ColumnDefinition>
<ColumnDefinition Width="2*"></ColumnDefinition>
<ColumnDefinition Width="3*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<Button Grid.Row="0" Grid.Column="0" Clicked="OnStartClicked" Image="play.png" BackgroundColor="Transparent" HorizontalOptions="Center" Grid.RowSpan="2"/>
<Label Grid.Row="0" Grid.Column="1" Text="Hora de Inicio: " XAlign="Center" YAlign="Center" TextColor="Black" FontAttributes="Bold"/>
<Label Grid.Row="0" Grid.Column="2" Text="{ Binding attribute3 }" XAlign="Center" YAlign="Center" TextColor="Black"/>
<Label Grid.Row="1" Grid.Column="1" Text="Encargado de la Tarea: " XAlign="Center" YAlign="Center" TextColor="Black" FontAttributes="Bold"/>
<Label Grid.Row="1" Grid.Column="2" Text="{ Binding attribute4 }" XAlign="Center" YAlign="Center" TextColor="Black"/>
<BoxView Color="Navy" HeightRequest="2" Grid.Row="2" Grid.Column="0" Grid.ColumnSpan="3"/>
</Grid>
</ViewCell.View>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>

Use data template based on property

Is it possible to control which DataTemplate a node used based on a property rather than the class type which is typically seen in wpf.
In my case I have a list of teams and I want to control the background of each team being listed in the listbox as well as a few other design elements such as displaying different logos based on which team. In my mind it seems easiest to just make a data template based on the team name.
How do you guys suggest I handle it. I don't want to create a class object for every entire team. However it would be ideal if a team doesn't have a design template that a default one gets used.
Either way if someone could put together a super simple example Id appreciate it considering im not sure how to do it .

From what you described, it seems to me that those property can be hold on the Team class and you could display the content based on them !, but since you might need something much complicated you could use a DataTemplateSelector basically what you need to do is :
First : In resources area define the DataTemplates that you need plus a default one, in case none of the teams names matche a difined template,
lets say something like that :
<Window.Resources>
<DataTemplate x:Key="DefaultnDataTemplate" DataType="{x:Type YourNameSpace:Team}">
<Grid Background="LightGreen">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<TextBlock Text="DefaultnDataTemplate"/>
<TextBlock Text="{Binding Id}" Grid.Row="1" Grid.Column="0"/>
<TextBlock Text="{Binding Name}" HorizontalAlignment="Center" Grid.Row="1" Grid.Column="1"/>
<TextBlock Text="{Binding Matches}" Grid.Row="1" Grid.Column="2"/>
</Grid>
</DataTemplate>
<DataTemplate x:Key="TeamADataTemplate" DataType="{x:Type YourNameSpace:Team}">
<Grid Background="LightCoral">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<TextBlock Text="TeamADataTemplate"/>
<TextBlock Text="{Binding Id}" Grid.Row="1" Grid.Column="0"/>
<TextBlock Text="{Binding Name}" HorizontalAlignment="Center" Grid.Row="1" Grid.Column="1"/>
<TextBlock Text="{Binding Matches}" Grid.Row="1" Grid.Column="2"/>
</Grid>
</DataTemplate>
<DataTemplate x:Key="TeamBDataTemplate" DataType="{x:Type YourNameSpace:Team}">
<Grid Background="LightBlue">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<TextBlock Text="TeamBDataTemplate"/>
<TextBlock Text="{Binding Id}" Grid.Row="1" Grid.Column="0"/>
<TextBlock Text="{Binding Name}" HorizontalAlignment="Center" Grid.Row="1" Grid.Column="1"/>
<TextBlock Text="{Binding Matches}" Grid.Row="1" Grid.Column="2"/>
</Grid>
</DataTemplate>
</Window.Resources>
Second add a DataTemplateSelector class, the class will basically check the team name and return the appropriate DataTemplate:
public class TeamDataTemplateSelector : DataTemplateSelector
{
public DataTemplate DefaultnDataTemplate { get; set; }
public DataTemplate TeamADataTemplate { get; set; }
public DataTemplate TeamBDataTemplate { get; set; }
public override DataTemplate SelectTemplate(object item,
DependencyObject container)
{
var teamName = (item as Team).Name;
switch (teamName)
{
case "TeamA":
return TeamADataTemplate;
case "TeamB":
return TeamBDataTemplate;
default:
return DefaultnDataTemplate;
}
}
}
Third, add an instance of that class to the StaticResources, and point it to the already defined DataTemplates :
<YourNameSpace:TeamDataTemplateSelector x:Key="TeamDataTemplateSelector" TeamADataTemplate="{StaticResource TeamADataTemplate}" TeamBDataTemplate="{StaticResource TeamBDataTemplate}" DefaultnDataTemplate="{StaticResource DefaultnDataTemplate}"/>
Finally call the TemplateSelector in your List:
<ListBox ItemsSource="{Binding Teams}" ItemTemplateSelector="{StaticResource TeamDataTemplateSelector}">
</ListBox>
here the model i am using in this sample :
public class Team
{
public string Name { get; set; }
public string Id { get; set; }
public string Matches { get; set; }
}
private ObservableCollection<Team> _teams=new ObservableCollection<Team>()
{
new Team()
{
Id="1",
Matches = "45",
Name = "TeamA"
},
new Team()
{
Id="1",
Matches = "45",
Name = "TeamB"
},
new Team()
{
Id="1",
Matches = "45",
Name = "TeamC"
}
};
public ObservableCollection<Team> Teams
{
get
{
return _teams;
}
set
{
if (_teams == value)
{
return;
}
_teams = value;
OnPropertyChanged();
}
}

Develop Reference

C# (C-Sharp) is a programming language developed by Microsoft that runs on the .NET Framework.

How to pass data between the View and the ViewModel - c#

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Binding a list of object to grid

Use data template based on property

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