I've been working on an application in MVVM Light lately. I have a TextBox in my XAML bound to my UI. I'd like to validate any input and ensure that only numbers are entered. I've tried the following code:
My TextBox:
<TextBox TabIndex="1" Height="23" MinWidth="410" DockPanel.Dock="Left"
HorizontalAlignment="Left"
Text="{Binding Input, UpdateSourceTrigger=PropertyChanged}"
IsEnabled="{Binding IsEnabled}"
AcceptsReturn="False"
local:FocusExtension.IsFocused="{Binding IsFocused}">
And in my ViewModel:
private string input;
public string Input
{
get { return this.input; }
set
{
decimal test;
if(decimal.TryParse(value, out test))
{
this.input = value;
}
else
{
this.input = "";
}
RaisePropertyChanged("Input");
}
}
This fails to update the UI. If I enter "B" and check the debugger, it runs through the setter, but fails to actually update the UI.
Curiously, if I set this.input = "TEST"; in the else block, the UI updates, but, if I attempt to set it to "", string.Empty, or the value of input before the validation, the UI fails to update.
Is this by design? Possibly a bug? Is there something I'm doing wrong?
Edit I mistakenly forgot to include RaisePropertyChanged in my example code. I've updated it. Raising it isn't the problem as I've watched the debugger run all the way through raising it and returning input via the getter.
Way you use strign type property and then convert to decimal, easier to change lik this:
public decimal Input
{
get { return this.input; }
set
{
this.input = value;
RaisePropertyChanged("Input");
}
}
And for validate use IDataErrorInfo (read more: http://blogs.msdn.com/b/wpfsdk/archive/2007/10/02/data-validation-in-3-5.aspx)
What we have done is created a Custom Control, since we use it for a Currency Text Box. I warn you I have no validation that this is a good idea, or falls in line with MVVM model because all manipulation of the control are done in code behind.
In the control on the textbox we have an event on PreviewTextInput that does this
e.Handled = Functions.DoubleConverter(Convert.ToChar(e.Text), ((TextBox)sender).Text.Replace("$", ""));
Then for the function (which isnt perfect, I have a few issues with it still) is:
static public bool DoubleConverter(char c, string str)
{
if (!char.IsDigit(c))
{
if (c == '.' && (str.Contains('.')))
{
return true;
}
else if (c != '.')
{
return true;
}
}
return false;
}
Please use this as a reference, not exactly as is because it is a very crude implementation.
Related
I inherited a project that uses the Xamarin Extended Forms controls. All of the text boxes on the form use this. I am trying to do something that feels very simple... I want to display and capture numbers and display them with thousands seperators. So, my odometer field displays 356,098 instead of 356098, much easier to read. It needs to save the integer without formatting in the binding.
I've tried various forms of string formatting on the text box and when my page loads I get an endless loop. It seems like the control formats the field and updates it which triggers the getter/setter which then tries to format it without the comma which triggers the textbox that there is a change, through the binding, and it adds the comma, which triggers another loop and on and on.
Here is the control.
<xfx:XfxEntry
Text="{Binding OdometerEntry, StringFormat='{0:N0}'}"
TextColor="{Binding TextColor}"
IsEnabled="{Binding READ_ONLY, Converter={StaticResource NegateBool}}"
FontSize="Medium"
Keyboard="Numeric"
Margin="10,-20,0,-20"
Grid.Row="2"
Grid.Column="1" />
And here is the model for that field:
public string OdometerEntry
{
get => _odometerEntry;
set
{
if (string.IsNullOrEmpty(value) || value == "0")
{
if (Inspection != null && Inspection.Truck != null)
{
Inspection.Truck.OdometerEntry = 0;
}
_odometerEntry = "";
}
else
{
int i = General.IntParseSafe(value);
if (i < 0)
{
i = 0;
}
if (Inspection != null && Inspection.Truck != null)
{
Inspection.Truck.OdometerEntry = i;
}
_odometerEntry = i.ToString();
}
OnPropertyChanged();
}
}
I tried adding formatting in the ToString but that did not work. I realize this form extender is no longer supported, but I'm hoping someone has some insight.
UPDATE
I tried using the regular Entry tag but same result. The string just will not format.
<Entry Text="{Binding OdometerEntry,StringFormat='{0:#,0}'}"
Rough sketch of the solution, off the top of my head:
int _numericValue;
string _previousString = "";
override OnTextChanged(...)
{
string newText = ...; // From a parameter to OnTextChanged.
if (string.Equals(newText, _previousString))
return; // Avoid infinite loop - this call caused by our change!
string formattedString = StringFormat("...", newText); // Apply desired format.
if (!string.Equals(formattedString, _previousString))
{
_previousString = formattedString;
// CAUTION: This triggers another call to `OnTextChanged`.
theTextField.Text = formattedString;
// TODO: Set cursor to end of text?
}
}
I have a combobox with a custom enum (just true/false). I have a function that checks conditions if the SelectedValue changes from false to true and if the conditions are wrong it changes the combobox SelectedValue back to false. This changes the SelectedValue to false if you check it in code, but when you look at the UI it's still on true.
Here's the xaml for the combobox:
<ComboBox x:Name="comboEnabled1" Width="80" Height="26"
ItemsSource="{Binding Path=TrueFalseChoices}"
SelectedValue="{Binding Path=Enable1, Mode=TwoWay}"/>
Here's the viewmodel
private TrueFalse _enable1 = TrueFalse.False;
public TrueFalse Enable1
{
get { return _enable1; }
set
{
if (_enable1 != value)
{
_enable1 = value;
base.OnPropertyChanged("Enable1");
OnEnableChanged(EventArgs.Empty);
}
}
}
And here's the function that I'm using to check the conditions
public void HandleEnable(object sender, EventArgs e)
{
if(Enable1 == TrueFalse.True)
{
if(!connected)
{
HandleMessage("Can't enable, not connected");
Enable1 = TrueFalse.False;
}
else if (!_main.CBCheck(_main.cbReason))
{
Enable1 = TrueFalse.False;
}
}
Console.WriteLine("Enabled {0}", Enable1);
}
Was thinking I'm changing the value too rapidly, but the last Console.Writeline produces the right outcome each time.
Any help appreciated!
Edit: Calling Handleenable here:
protected void OnEnableChanged(EventArgs e)
{
EventHandler handler = EnableChanged;
if (handler != null)
handler(this, e);
}
And in the ViewModel funct:
EnableChanged += HandleEnable;
Changing the Enable1 in any other place worked as it should have, only having issues in HandleEnable function.Also tried changing other comboboxes in the HandleEnable function and that worked as it should have.
I would recommend actually disabling the ComboBox if the requirements are not met.
But if you insist on reverting Enable1 back to False if conditions are not met, you should push the notification properly through the dispatcher.
set
{
var effectiveValue = condition ? value : TrueFalse.False;
if (effectiveValue == TrueFalse.False && value == TrueFalse.True)
System.Windows.Threading.Dispatcher.CurrentDispatcher.BeginInvoke(
new Action(() => base.OnPropertyChanged("Enable1"), null));
//your regular set-code follows here
}
It happens because WPF is already responding to that event, and therefore ignoring the subsequent calls until it's done. So you immediately queue another pass as soon as the current one is finished.
But I would still recommend disabling the ComboBox when it is effectively disabled. Accessing the dispatcher from a viewmodel does not smell good no matter how you look at it.
UPD: You can also solve that with {Binding Enable1, Delay=10} if your framework is 4.5.1+.
SOLUTION IS IN EDIT OF THE ACCEPTED ANSWER
I have a view in which has two Pickers, I need to have it so that when the SelectedItem property in one Picker changes, the list of Items in the second Picker (ItemSource) changes as well.
Currently I have a bound the SelectedItem and SelectedIndex properties of both pickers to properties in my ViewModel. In the setter(s) for both of them, I perform the logic needed to change the list of Items in the second picker. The list of Items in the second picker changes successfully, but when I set the SelectedIndex (to make it select an Item by default), this fails if the index which I am setting it to is the same as the index which it was on in the previous list. It just shows the Title of the Picker instead, this issue seems to be related to this bug.
My Code:
Both Pickers are bound to an Observable collection of strings FYI
FrameType and DirectionType are Enums
I initially used only the SelectedItem property
Relevant XAML
<Label Grid.Row="1" Grid.Column="0" VerticalTextAlignment="Center"
Text="Direction: " />
<Picker x:Name="PickerDirection" Grid.Row="1" Grid.Column="1"
Title="Select Direction"
ItemsSource="{Binding Directions}"
SelectedItem="{Binding SelectedDirection}"
SelectedIndex="{Binding SelectedDirectionIndex}"></Picker>
<Label Grid.Row="2" Grid.Column="0" VerticalTextAlignment="Center"
Text="Frame: "/>
<Picker x:Name="PickerFrame" Grid.Row="2" Grid.Column="1"
Title="Select Frame"
ItemsSource="{Binding Frames}"
SelectedItem="{Binding SelectedFrame}"
SelectedIndex="{Binding SelectedFrameIndex}"></Picker>
Relevant View Model code:
public string SelectedDirection
{
get { return _selectedDirection; }
set
{
if (Directions.Contains(value))
{
if (_selectedDirection != value)
{
if (EnumUtils.ToEnumFromString<FrameType>(SelectedFrame) == FrameType.Road &&
!DirectionsRoad.Contains(value))
{
_selectedDirection = Directions[Directions.IndexOf(DirectionType.Right.ToString())];
}
else
{
_selectedDirection = value;
}
OnPropertyChanged();
}
}
}
}
public string SelectedFrame
{
get { return _selectedFrame; }
set
{
if (_selectedFrame != value)
{
_selectedFrame = value;
if (EnumUtils.ToEnumFromString<FrameType>(_selectedFrame) == FrameType.Road)
{
Directions = DirectionsRoad;
if (Directions.Contains(SelectedDirection))
{
SelectedDirectionIndex = Directions.IndexOf(SelectedDirection);
}
else
{
SelectedDirectionIndex = Directions.IndexOf(DirectionType.Right.ToString());
}
}else if (EnumUtils.ToEnumFromString<FrameType>(_selectedFrame) == FrameType.Lane)
{
Directions = DirectionsAll;
SelectedDirectionIndex = Directions.IndexOf(SelectedDirection);
}
OnPropertyChanged();
}
}
}
}
public int SelectedDirectionIndex
{
get { return _selectedDirectionIndex; }
set
{
if (_selectedDirectionIndex != value)
{
if (!(value < 0 || value >= Directions.Count))
{
_selectedDirectionIndex = value;
OnPropertyChanged();
}
}
}
}
public int SelectedFrameIndex
{
get { return _selectedFrameIndex; }
set
{
if (_selectedFrameIndex != value)
{
if (!(value < 0 || value >= Frames.Count))
{
_selectedFrameIndex = value;
OnPropertyChanged();
}
}
}
}
The outcome:
I expect it to never be empty since I ensure that the SelectedDirection is always set to something.
Notes:
I initially used just the SelectedItem property, but when I encountered this bug I thought using the SelectedIndex property would help to fix it.
I used ObservableCollection to maintain consistency with the other viewModels in the project, and to ensure that the options in the picker are updated when I make changes (based on my understanding you need to use ObservableCollection to make this possible).
I do plan to refactor the code in the setter for SelectedFrame into smaller functions as soon as I get things to work.
Due to this It seems that using the SelectedIndexChanged event of the Picker would be the only way to fix this. However the comment by ottermatic in this question says that events are unreliable. Hence I felt is was better to perform this logic in the setter.
If someone could comment on what I may be doing wrong in my code which is causing this issue and also comment on the pros/cons and/or whether or not I should use the eventHandler or have the logic in my setter. Thanks
I don't really see why you are using both SelectedItem and SelectedIndex, but I think what you are trying to achieve can be achieved easier.
First of all, I don't think you need ObservableCollection types at all in your example, since you are setting the directions anyway and not modifying the collection. More importantly, fiddling around with the indices is completely unnecessary, as far as I can tell. You are using strings anyway and even though String is not a value type, but a reference type, you cannot practically distinguish two String instances that have the same content, hence assinging the respective values to SelectedDirection and SelectedFrame is sufficient.
The following checks seem redundant to me
if (Directions.Contains(value))
if (EnumUtils.ToEnumFromString<FrameType>(SelectedFrame) == FrameType.Road &&
!DirectionsRoad.Contains(value))
since Directions are set to DirectionsRoad anyway if SelectedFrame has been set to "Road". Hence I'd assume that the second condition won't evaluate to true in any case. Hence the SelectedDirection can be simplified:
public string SelectedDirection
{
get => _selectedDirection;
set
{
if (_selectedDirection != value && Directions.Contains(value))
{
_selectedDirection = value;
OnPropertyChanged();
}
}
}
Within the setter of SelectedFrame there are many things going on, which I'd refactor to methods on it's own right, to improve clarity.
public string SelectedFrame
{
get => _selectedFrame;
set
{
if (_selectedFrame != value)
{
_selectedFrame = value;
UpdateAvailableDirections();
OnPropertyChanged();
}
}
}
private void UpdateAvailableDirections()
{
// store the selected direction
var previouslySelectedDirection = SelectedDirection;
Directions = GetValidDirectionsByFrameType(EnumUtils.ToEnumFromString<FrameType>(SelectedFrame));
SelectedDirection = GetSelectedDirection(previoslySelectedDirection, Directions);
}
private string[] GetValidDirectionsByFrameType(FrameType frameType)
{
return frameType == FrameType.Road ? DirectionsRoad : DirectionsAll;
}
private string GetSelectedDirection(string previouslySelectedDirection, string[] validDirections)
{
return validDirections.Contains(previouslySelectedDirection) ? previouslySelectedDirection : DefaultDirection;
}
By setting the SelectedItem instead of fiddling with the indices, the correct values shall be displayed.
Concerning your question whether this logic may be better suited in an event handler or in the setter depends on your requirements. If all you need is the index, the event SelectedIndexChanged may work out for you, but if the value is needed in several places and methods that are not called by the event handler, the presented solution may be more viable.
Edit
You were correct, it has got nothing to do with the usage of SelectedIndex and SelectedItem. The issue is a bit more subtle.
I build a quick proof-of-concept and found the following:
Assuming SelectedDirection is "Right" (and the index is set accordingly)
When Directions is set, the SelectedItem on the picker seems to be reset
SelectedDirection is set to null
this.Directions.Contains(value) evaluates to false, hence _selectedDirection is not set (this hold true for SelectedDirectionIndex, since the value -1 is filtered by if(!value < 0 || value >= this.Directions.Count))
When SelectedDirection is set afterwards, the value is still "Right", hence OnPropertyChanged is not called (since the values are the same) and the SelectedItem is not set
This way there is a mismatch between the value the Picker actually holds and the property in the viewmodel, which leads to unexpected behavior.
How to mitigate the issue?
I'd still stick with the code without the indices (unless you really need them) and use the string values.
There are other possibilities, but I'd change the setter of SelectedDirection. When you allowed the value to be set to null, PropertyChanged will be raised properly when the value is set to Right afterwards. If you really need to filter what the value is set to, you should still raise OnPropertyChanged, to inform the Picker that the value has changed (preventing a mismatch between the actual Pickers value and the viewmodel)
public string SelectedDirection
{
get => _selectedDirection;
set
{
if (_selectedDirection != value)
{
if(Directions.Contains(value))
{
_selectedDirection = value;
}
else
{
_selectedDirection = DirectionTypes.Right.ToString();
}
OnPropertyChanged();
}
}
}
Found a somewhat hacky fix for this, and it seems to be a Xamarin issue. I have made the following changes to my code"
The relevant changes are in the setter for SelectedFrame:
public string SelectedFrame
{
get { return _selectedFrame; }
set
{
if (_selectedFrame != value)
{
_selectedFrame = value;
if (EnumUtils.ToEnumFromString<FrameType>(_selectedFrame) == FrameType.Road)
{
Directions = DirectionsRoad;
if (Directions.Contains(SelectedDirection))
{
/*Relevant edits*/
var position = Directions.IndexOf(SelectedDirection);
SelectedDirection = Directions[Directions.Count - position -1];
SelectedDirection = Directions[position];
}
else
{
SelectedDirectionIndex = Directions.IndexOf(DirectionType.Right.ToString());
}
}else if (EnumUtils.ToEnumFromString<FrameType>(_selectedFrame) == FrameType.Lane)
{
Directions = DirectionsAll;
/*Relevant edits*/
var position = Directions.IndexOf(SelectedDirection);
SelectedDirection = Directions[Directions.Count - position -1];
SelectedDirection = Directions[position];
}
OnPropertyChanged();
}
}
}
}
It seems that my issue arises when I change the contents of my ObservableCollectoin but the SelectedDirection stays the same.
When I change Directions (which is an ObservableCollection) by assigning it to DirectionsAll (also an ObservableCollection), I need to make sure that the SelectedDirection changes,. The added code ensures that a change actually occurs to SelectionDirection and that fixes it. Seems somewhat hacky but it works.
Outcome:
I encountered a problem with the IDataErrorInfo Interface and a wizard I'm currently programming.
The intention of my programm is to ask some Inputs ( usually done with a barcode scanner) and depending on the inputs start a specific sequence.
This is working as intendet. To make sure to catch wrong scans all inputs are check with an event ( OnValueParseFailed) If this event is triggered my current textbox is focused and all text selected:
this.MyWizardViewModel.ValueParseFailed += (s, e) =>
{
switch (e.Parameter)
{
case "ProductionOrder":
this.TextBoxProduction.Focus();
this.TextBoxProduction.SelectAll();
break;
The Interface itself is included this way:
public string this[string name]
{
get
{
string result = null;
if ((name == "ProductionOrder") && (!string.IsNullOrEmpty(this.ProductionOrder)))
{
if (this.System.FirmwareVersion == 0)
result = Lang.Strings.WrongEntry;
}
Its working for the first run. But if the wizard is finished or aborted and run a second time without closing the app, no error message is shown.
The Reset simply returns the app to default values.
public void ResetApplikation()
{
this.System.Clear(); // reset System values
this.ProductionOrder = string.Empty;
this.BmsTypeCode = string.Empty;
this.CellStack1TypeCode = string.Empty;
this.CellClass1 = string.Empty;
this.CellStack2TypeCode = string.Empty;
this.CellClass2 = string.Empty;
this.IsSystemProgrammed = false;
this.IsSystemParameterized = false;
this.MyMachine.Abort(); // reset wizard state
}
While debugging I can see the Interface to be handeled correctly. But no error is displayed.
In XAML the binding is set TwoWay
<TextBox Name="TextBoxProduction" Grid.Row="2" Width="200" Margin="10"
Style="{StaticResource TextBoxNormal}" Loaded="TextBoxProduction_Loaded"
Text="{Binding Path=ProductionOrder, ValidatesOnDataErrors=True,
NotifyOnValidationError=True, Delay=100,
UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" />
I'm using MahApps but as the textbox class is based on the wpf textbox I doubt a bug in this element is the problem. Any suggestions would be great.
Thank you.
The Answer of Domysee helped me.
Implementing INotifyDataErrorInfo instead of IDataErrorInfo was a major change but it fixed the problem!
public string TenNguoiDung
{
get { return _currentNguoiDung.TenNguoiDung; }
set
{
_currentNguoiDung.TenNguoiDung = value != null
? value.ToStandardString(true) : string.Empty;
SendPropertyChanged("TenNguoiDung");
ValidProperty(_currentNguoiDung.TenNguoiDung, new
ValidationContext(_currentNguoiDung) { MemberName = "TenNguoiDung" });
}
}
public static string ToStandardString(this string value,
bool isAllStartWithUpper = false)
{
string result = string.Empty;
value = value.Trim();
var listWord = value.Split(' ').ToList();
listWord.RemoveAll(p => p == string.Empty);
foreach (var item in listWord) result +=
item.Substring(0, 1).ToUpper() + item.Substring(1).ToLower() + " ";
if (!isAllStartWithUpper) result =
result.Substring(0, 1) + result.Substring(1).ToLower();
return result.Trim();
}
I have a TextBox:
<TextBox Grid.Column="1" Margin="1" Text=
"{Binding Path=TenNguoiDung,Mode=TwoWay,NotifyOnValidationError=True}"/>
When i typed some clear text to Standard, Setter called SendPropertyChanged("TenNguoiDung") but on UI not update. How can i fix that??
Edit:
public void SendPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
Edit:
I debuged at Setter, i saw _currentNguoiDung.TenNguoiDung changed after ToStandardString, but on UI was not updated
Update
I used few hours to google and i got my answer.
I feel happy when this bug only happen on debug mode. When i run application without debug, it work perfect!!
Fix debug Mode:
[link]Coerce Value in Property Setter - Silverlight 5
Right click on the Web project in Solution Explorer and select
Properties.
Select the Web tab.
Scroll down to the Debuggers section.
Uncheck the checkbox labelled Silverlight.
Make sure you are setting the data context to the instance of the class containing your property.
From the looks of it you are doing this but make sure you are implementing INotifyPropertyChanged
When debugging if you have any binding errors happening these will show in the output window.
Is the value changing if you type in 'hello' and then replace it with 'world'? If so it may just be a case sensitivity issue