Develop Reference

How to pass parameters with shell navigation before binding

I am writing a program using Xamarin, Shell and MVVM.I want to send a parameter to next page and I am using the following code:
await Shell.Current.GoToAsync($"//{nameof(CopyBooksPage)}?RegisteredUserId={registeredUser.Id}");
Question: How to get the parameter before binding?
First wrong solution:
In CopyBooksPage.xaml I have binding to properties in VM but I have no affiliation with the VM.
I do this:
[XamlCompilation(XamlCompilationOptions.Compile)]
[QueryProperty(nameof(RegisteredUserId), "RegisteredUserId")]
public partial class CopyBooksPage : ContentPage
{
private int _registeredUserId;
public int RegisteredUserId
{
get { return _registeredUserId; }
set
{
_registeredUserId = value;
CopyBooksViewModel copyBooksViewModel = App.GetViewModel<CopyBooksViewModel>();
copyBooksViewModel.RegisteredUserId = _registeredUserId;
BindingContext = copyBooksViewModel;
copyBooksViewModel.RefreshBinding();
}
}
public CopyBooksPage()
{
InitializeComponent();
}
}
Call order:
construktor
properties RegisteredUserId
The problem is twofold.
After calling the constructor, I get information about binding errors (because there is no VM). It's not annoying but I want (need) to get rid of it.
I do the binding only in the propertis and this causes the problem that for each VM propertis I have to call the OnPropertyChanged method to refresh the binding. And this is troublesome for me. I do not want to do it.
Second wrong solution
Code behind:
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class CopyBooksPage : ContentPage
{
public CopyBooksPage()
{
InitializeComponent();
BindingContext = App.GetViewModel<CopyBooksViewModel>();
}
}
ViewModel:
class CopyBooksViewModel : BaseViewModel, IQueryAttributable
{
private int registeredUserId;
//read from database
private CopyBook copyBookModel;
public string BookTitle
{
get { return copyBookModel.Title; }
set
{
copyBookModel.Title = value;
OnPropertyChanged(nameof(Title));
}
}
public CopyBooksViewModel()
{
}
public void ApplyQueryAttributes(IDictionary<string, string> query)
{
if (query.ContainsKey("RegisteredUserId"))
{
registeredUserId = int.Parse(HttpUtility.UrlDecode(query["RegisteredUserId"]));
copyBookModel = ReadFromDatabase(registeredUserId);
}
}
}
Call order:
construktor
Binding
method ApplyQueryAttributes
When binding the BookTitle, I reference the copyBookModel which is null. I could secure it.
The problem is that the ApplyQueryAttributes method is called last. In it again I would have to call OnPropertyChanged for all propertis. I do not want to do it.

TextBlock Inline Binding using DependencyProperty [duplicate]

This question already has answers here:
DependencyProperty getter/setter not being called
(2 answers)
Closed 7 years ago.
I'm using MVVMLight. This is what I have from an example here.
private ObservableCollection<Inline> _inlineList;
public ObservableCollection<Inline> InlineList
{
get { return _inlineList; }
set { Set(() => InlineList, ref _inlineList, value); }
}
private void SendClicked()
{
InlineList.Add(new Run("This is some bold text") { FontWeight = FontWeights.Bold });
InlineList.Add(new Run("Some more text"));
InlineList.Add(new Run("This is some text") { TextDecorations = TextDecorations.Underline });
}
public class BindableTextBlock : TextBlock
{
public ObservableCollection<Inline> InlineList
{
get { return (ObservableCollection<Inline>)GetValue(InlineListProperty); }
set { SetValue(InlineListProperty, value); }
}
public static readonly DependencyProperty InlineListProperty =
DependencyProperty.Register("InlineList", typeof(ObservableCollection<Inline>), typeof(BindableTextBlock), new UIPropertyMetadata(null, OnPropertyChanged));
private static void OnPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
if (e.NewValue == null) return;
var textBlock = (BindableTextBlock)sender;
textBlock.Inlines.AddRange((ObservableCollection<Inline>)e.NewValue);
}
}
<testRobot:BindableTextBlock
Width="Auto" Height="Auto"
InlineList="{Binding InlineList}" >
</testRobot:BindableTextBlock>
The problem is that bound property InlineList never gets updated. I don't see any text I add to the collection ObservableCollection. When I put a break point in OnPropertyChanged method it never gets hit. I know my data context is set correctly as other bound controls work.
What could be the problem?

Ok you only need to add these in your BindableTextBlock With your Original solution. What we do here is we add handler for when collection is changed (meaning new values are added), we only do that when the collection is set. So with the binding that you have in your xaml every change you make on the collection in the VM fires collection changed event in the textblock which in turn just appends values to the Inline.
private void CollectionChangedHandler(object sender, NotifyCollectionChangedEventArgs e)
{
Inlines.AddRange(e.NewItems);
}
private static void OnPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
if (e.NewValue == null) return;
var textBlock = (BindableTextBlock)sender;
textBlock.InlineList.CollectionChanged += textBlock.CollectionChangedHandler;
}
BEFORE EDIT for history reasons
Ok I saw what's happening so first the explanation then an example.
So first some basic concepts about wpf:
In order to have your view notified for a change in bound variable in your ViewModel (or whatever that is DataContext at the moment) you have to either RaisePropertyChanged event with the name of the changed property or use something that's doing this somehow :) - like ObservableCollection.
So some use cases:
You have a property with field -> it is common practice to have it like this:
private ICollection<Inline> _inlineList;
public ICollection<Inline> InlineList
{
get
{
return _inlineList;
}
set
{
_inlineList = value;
RaisePropertyChanged("InlineList");
}
}
This ensures that when you set a new value to InlineList the view will be notified
Or in your case what I've used:
private ICollection<Inline> _inlineList;
public ICollection<Inline> InlineList
{
get { return _inlineList; }
set { Set(() => InlineList, ref _inlineList, value); }
}
If you check the description of Set method you'll see that it is setting the value and raising the property (and some more stuff)
You want to have automatic updates and use ObservableCollection -> I use it like this:
private ObservableCollection<ClientFilter> clientFilters;
public IEnumerable<ClientFilter> ClientFilters
{
get
{
if (this.clientFilters == null)
{
this.clientFilters = new ObservableCollection<ClientFilter>();
}
return this.clientFilters;
}
set
{
if (this.clientFilters == null)
{
this.clientFilters = new ObservableCollection<ClientFilter>();
}
SetObservableValues<ClientFilter>(this.clientFilters, value);
}
}
The method SetObservableValues is in my main ViewModel and is doing this:
public static void SetObservableValues<T>(
ObservableCollection<T> observableCollection,
IEnumerable<T> values)
{
if (observableCollection != values)
{
observableCollection.Clear();
foreach (var item in values)
{
observableCollection.Add(item);
}
}
}
This method ensures that if the reference to the obs collection is not the same it will clear the old one and reuse it, because when you bind you bind to the reference at common mistake is to then change the reference itself not the values, which in turn doesn't update anything on the UI and you think binding is broken :)
So If you want it to function normally you just add/remove to the Collection/Enumerable ClientFilters
Now the solution
So I'm not 100% sure what you want to achieve but here's what you could do in order to have your binding working
Your ViewModel
using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Command;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Documents;
namespace WpfApplication3.ViewModel
{
public class MainViewModel : ViewModelBase
{
public MainViewModel()
{
}
private ICollection<Inline> _inlineList;
public ICollection<Inline> InlineList
{
get { return _inlineList; }
set { Set(() => InlineList, ref _inlineList, value); }
}
public RelayCommand SendClicked
{
get
{
return new RelayCommand(() =>
{
InlineList = new List<Inline>
{
new Run("This is some bold text") { FontWeight = FontWeights.Bold },
new Run("Some more text"),
new Run("This is some text") { TextDecorations = TextDecorations.Underline }
};
});
}
}
}
}
Your custom control -> BindableTextBlock
using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
namespace WpfApplication3
{
public class BindableTextBlock : TextBlock
{
public ICollection<Inline> InlineList
{
get { return (ICollection<Inline>)GetValue(InlineListProperty); }
set { SetValue(InlineListProperty, value); }
}
public static readonly DependencyProperty InlineListProperty =
DependencyProperty.Register("InlineList", typeof(List<Inline>), typeof(BindableTextBlock), new UIPropertyMetadata(null, OnPropertyChanged));
private static void OnPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
if (e.NewValue == null) return;
var textBlock = (BindableTextBlock)sender;
textBlock.Inlines.AddRange((ICollection<Inline>)e.NewValue);
}
}
}
Your XAML
On your Page or Window (depending on platform)
DataContext="{Binding Main, Source={StaticResource Locator}}"
Then inside
<StackPanel>
<Button Command="{Binding SendClicked}">SendClicked</Button>
<local:BindableTextBlock Background="Black" Foreground="AliceBlue"
Width = "Auto" Height="Auto"
InlineList="{Binding InlineList}"
>
</local:BindableTextBlock>
</StackPanel>
All assuming you have your ViewModelLocator from MVVM Light register your view model
using GalaSoft.MvvmLight.Ioc;
using Microsoft.Practices.ServiceLocation;
namespace WpfApplication3.ViewModel
{
public class ViewModelLocator
{
public ViewModelLocator()
{
ServiceLocator.SetLocatorProvider(() => SimpleIoc.Default);
SimpleIoc.Default.Register<MainViewModel>();
}
public MainViewModel Main
{
get
{
return ServiceLocator.Current.GetInstance<MainViewModel>();
}
}
public static void Cleanup()
{
}
}
}
ALTERNATIVE
Alternatively you could have your command like this:
public RelayCommand SendClicked
{
get
{
return new RelayCommand(() =>
{
_inlineList = new List<Inline>();
InlineList.Add(new Run("This is some bold text") { FontWeight = FontWeights.Bold });
InlineList.Add(new Run("Some more text"));
InlineList.Add(new Run("This is some text") { TextDecorations = TextDecorations.Underline });
RaisePropertyChanged("InlineList");
});
}
}
But you have to use the other option of defining the property as described at the beginning of my post.
You could do it in other ways of course.
Just one more advice -> It is considered bad practice and not in the spirit of MVVM to have UI elements in your view model, so change in architecture is strongly advised in this code IMO.
Post got too long (as usual), if you need aditional explanation please let me know.
Cheers and happy coding ;)

Winforms How to Bind to a List<long> DatagridView and have it show correctly

So I need to show in a Grid a list of numbers that people enter to help them double check their work. It almost works except it doesn't show the numbers. My setup is simple. I have a textbox, they enter the number, when the add button is clicked its added to a BindingList and then that is used as the datasource for the DataGridView.
So, with some help from this Stackoverflow Post I was able to get this halfway working.
Unfortunately, even though it appears to add a row the Grid each time it does not correctly show the value. It shows the new rows as empty.
Here is my code.
public partial class ManualEntry : Form
{
BindingList<long> ProjectIDs;
public ManualEntry()
{
InitializeComponent();
ProjectIDs = new BindingList<long>();
}
When the add button is clicked, this gets executed.
private void AddButton_Click(object sender, EventArgs e)
{
try
{
long temp = long.Parse(textBox1.Text);
ProjectIDs.Add(temp);
ProjectsGrid.DataSource = ProjectIDs;
textBox1.Text = "";//clear the textbox so they can add a new one.
}
catch//bring up the badinput form
{
BadInput b = new BadInput();
b.Show();
}
}
And so here is the result of adding a few numbers.
If you need any other code from me to help you answer the question, just ask.

You haven't told the DataGridViewColumn what to bind to.
Normally you bind to a public property of the bound data type. In this case your data type is long which does not have an appropriate property to bind to.
Wrap your long in a custom class and expose it as a public property.
public class Data
{
public long Value { get; set; }
}
Bind your column to the Value property. You can do this in the designer, but here is the code:
Column1.DataPropertyName = "Value";
Now instead of long you use Data:
ProjectIDs = new BindingList<Data>();
...
long temp = long.Parse(textBox1.Text);
ProjectIDs.Add(new Data { Value = temp });

The following post discusses this:
DataGridView bound to BindingList does not refresh when value changed
It looks like your data type in the binding list needs to support the INotifyPropertyChanged interface:
http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged.aspx
NOTE: Revised - my use of INotifyPropertyChanged was incorrect and also appears not to be needed.
Now this answer is basically just like Igby's - so I think his is the better one :)
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
ProjectIDs = new BindingList<AwesomeLong>();
var source = new BindingSource( ProjectIDs, null );
dataGridView1.DataSource = source;
dataGridView1.Columns.Add( new DataGridViewTextBoxColumn() );
}
BindingList<AwesomeLong> ProjectIDs;
private int i = 0;
private void button1_Click( object sender, EventArgs e )
{
i++;
ProjectIDs.Add(new AwesomeLong(i));
}
}
public class AwesomeLong
{
public long LongProperty { get; set; }
public AwesomeLong( long longProperty )
{
LongProperty = longProperty;
}
}
}

How do I "Invalidate" after adding items to a collection property?

I am creating a Custom control in where I am creating a property of the type "List"
Sections is a public class which has 4 properties.
The code in the control looks as follows:
public partial class genericGauge : Control
{
public genericGauge()
{
InitializeComponent();
}
// Stripped out code not needed for this issue question.
private List<Sections> indicators = new List<Sections>();
public List<Sections> Indicators
{
get
{
return indicators;
}
}
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
// Stripped out code not needed for this issue question.
}
}
The Sections Class is as follows:
public class Sections
{
private string header = "Section1";
public string Header
{
get {return header;}
set
{
header = value;
}
}
private float startvalue = 0.0f;
public float StartValue
{
get { return startvalue; }
set
{
startvalue = value;
}
}
private float sweepvalue = 0.0f;
public float SweepValue
{
get { return sweepvalue; }
set
{
sweepvalue = value;
}
}
private Color sectioncolor = new Color();
public Color SectionColor
{
get {return sectioncolor;}
set
{
sectioncolor = value;
}
}
}
Everything seems to work fine except that when I add items to the collection at designtime using the property browsers typeeditor the control is not repainted to reflect what is added to the collection.
When I click outside the control on my testform it is repainted.
Usually with simple properties I would use Invalidate, but this seems not to be possible here.
I also tried with other collection types than List<> where it is allowed to have a set accessor, but Invalidate still wont be called. I assume that it means that the SET is never called.
I know how to get this to work with expandable properties but I have no luck finding how to make this update with collections.
I hope someoone can help me out.
thanks in advance.

Instead of using the class List, use the class ObservableCollection, and use that to get notified when a new section is added or removed from the list.
private ObservableCollection<Sections> indicators = new ObservableCollection<Sections>();
public IList<Sections> Indicators
{
get
{
return indicators;
}
}
public genericGauge()
{
InitializeComponent();
this.indicators.CollectionChanged += this.IndicatorsCollectionChanged;
}
private void IndicatorsCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
// possibly inspect the NotifyCollectionChangedEventArgs to see if it's a change that should cause a redraw.
// or not.
this.Invalidate();
}

When using your example exactly as it was the Indicators property was not available for editing in the property window. So I made a few changes to it.
I added a new class:
// Added this class to deal with the Sections class
public class SectionObservable : ObservableCollection<Sections>
{
// Added a few methods here for creating a designtime collection if I need to.
}
Then I made the change as you suggested
public genericGauge()
{
InitializeComponent();
this.indicators.CollectionChanged += this.IndicatorsCollectionChanged; // your suggestion
}
And made the property like this instead:
private SectionObservable indicators = new SectionObservable(); // using the SectionObservable class instead
public SectionObservable Indicators // using the SectionObservable class instead
{
get
{
return indicators;
}
}
private void IndicatorsCollectionChanged(object sender, NotifyCollectionChangedEventArgs e) // your suggestion
{
this.Invalidate();
}
And now works as a charm.
Thank you very much. I appreciate to see that it IS possible to get help this fast. I like this forum alot.

C# user control crashing VS11

I'm finding myself coding C3 for the first time, and using Visual Studio for the first time in a looong time.
I'm creating a user control that allows for picking a file/folder etc, for making that kindof control easier to implement in the future. However whenever I drag the control unto any form, Visual Studio crashes instantly. I have tried rebuilding the entire solution several times.
The error seems to only happen when creating public variables in the control...
Does anyone know how to get around this?
Code is work in progress.... ;)
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace BackupReport.tools
{
public partial class pathchooser : UserControl
{
#region "Datatypes"
public enum DLG { Folder, FileSave, FileOpen };
#endregion
#region "public properties"
public DLG Dtype
{
get
{
return this.Dtype;
}
set
{
this.Dtype = value;
}
}
public string labelText
{
get
{
return this.labelText;
}
set
{
this.labelText = value;
label1.Text = this.labelText;
}
}
#endregion
#region "Constructor"
public pathchooser()
{
InitializeComponent();
this.Dtype = DLG.Folder;
this.labelText = "Source:";
label1.Text = this.labelText;
}
#endregion
private void browse_button_Click(object sender, EventArgs e)
{
switch (this.Dtype)
{
case DLG.Folder:
if (fbd.ShowDialog() == DialogResult.OK)
{
path_textbox.Text = fbd.SelectedPath;
}
break;
case DLG.FileSave:
break;
case DLG.FileOpen:
break;
default:
break;
}
}
}
}
Any help would be appreciated.
also I'm not sure it matters, but I'm using VS11 beta.
//Martin

public DLG Dtype
{
get
{
return this.Dtype;
}
set
{
this.Dtype = value;
}
}
You have a property referring to itself, and thus calling its own getter and setter inside (respectively) the getter and setter. Something more appropriate would either be to either have empty accessors:
public DLG DType{get; set;}
or to have accessors referring to private variables:
private DLG dtype;
public DLG Dtype
{
get
{
return this.dtype;
}
set
{
this.dtype = value;
}
}

I think your properties are causing a StackOverflowException because the getters and setters invoke themselves in an endless loop (Dtype -> Dtype -> Dtype ...).
Try this code instead:
private string labelText;
public DLG Dtype { get; set; }
public string LabelText
{
get { return this.labelText; }
set
{
this.labelText = value;
label1.Text = value;
}
}