I am creating custom transport controls.
I want to have a Visibility control for a custom Button which I have created. So I have created a Property for it. In that Property, I have used GetTemplateChild("CompactOverlayButton") as Button to get the particular button but it returns null.
Here is my code
public bool IsCompactOverlayButtonVisible
{
get
{
var compactOverlayButton = GetTemplateChild("CompactOverlayButton") as Button;
if (compactOverlayButton.Visibility == Visibility.Visible)
return true;
else
return false;
}
set
{
var compactOverlayButton = GetTemplateChild("CompactOverlayButton") as Button;
if (value)
compactOverlayButton.Visibility = Visibility.Visible;
else
compactOverlayButton.Visibility = Visibility.Collapsed;
}
}
But the same line of code returns proper value in OnApplyTemplate() function.
Here is my code for OnApplyTemplate()
protected override void OnApplyTemplate()
{
var compactOverlayButton = GetTemplateChild("CompactOverlayButton") as Button;
compactOverlayButton.Click += CompactOverlayButton_ClickAsync;
base.OnApplyTemplate();
}
IsCompactOverlayButtonVisible probably gets evaluated for the first time before OnApplyTemplate(), meaning that the first time it gets evaluated, the template hasn't been applied and the button doesn't exist yet. In OnApplyTemplate(), get the button and assign it to a private field.
private Button _compactOverlayButton;
protected override void OnApplyTemplate()
{
base.OnApplyTemplate();
_compactOverlayButton = GetTemplateChild("CompactOverlayButton") as Button;
_compactOverlayButton.Click += CompactOverlayButton_ClickAsync;
}
And before you try to touch the button's properties, make sure it's not null.
public bool IsCompactOverlayButtonVisible
{
get
{
return _compactOverlayButton != null
&& _compactOverlayButton.Visibility == Visibility.Visible;
}
set
{
if (_compactOverlayButton != null)
{
compactOverlayButton.Visibility = value
? Visibility.Visible
: Visibility.Collapsed;
}
}
}
If something will set this value before the template is applied, for example if it's a public property of the control that may be set in XAML (which it sure looks like it is), you can't do it this way. You need to make it a regular dependency property, give it a PropertyChanged handler that updates the button's visibility if the button exists, and add a line in OnApplyTemplate() to update the actual button when you get your hands on it. Then it'll be usable as a target of a binding as well.
Update
And here's how you do that. This is the right way.
private Button _compactOverlayButton;
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
_compactOverlayButton = GetTemplateChild("CompactOverlayButton") as Button;
// Update actual button visibility to match whatever the dependency property value
// is, in case XAML gave us a value for it already.
OnIsCompactOverlayButtonVisibleChanged();
_compactOverlayButton.Click += CompactOverlayButton_Click;
// Secondly, just in case something in the XAML may change the button's visibility,
// put a watch on the property and update our dependency property to match when that
// changes.
var dpd = DependencyPropertyDescriptor.FromProperty(Button.VisibilityProperty, typeof(Button));
dpd.AddValueChanged(_compactOverlayButton, CompactOverlayButton_VisibilityChanged);
}
protected void CompactOverlayButton_VisibilityChanged(object sender, EventArgs args)
{
IsCompactOverlayButtonVisible = _compactOverlayButton.Visibility == Visibility.Visible;
}
private void CompactOverlayButton_Click(object sender, RoutedEventArgs e)
{
// ...whatever
}
#region IsCompactOverlayButtonVisible Property
public bool IsCompactOverlayButtonVisible
{
get { return (bool)GetValue(IsCompactOverlayButtonVisibleProperty); }
set { SetValue(IsCompactOverlayButtonVisibleProperty, value); }
}
public static readonly DependencyProperty IsCompactOverlayButtonVisibleProperty =
DependencyProperty.Register(nameof(IsCompactOverlayButtonVisible), typeof(bool), typeof(CustomMediaTransportControls),
new FrameworkPropertyMetadata(true,
FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,
IsCompactOverlayButtonVisible_PropertyChanged));
protected static void IsCompactOverlayButtonVisible_PropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
// It's a hassle to do stuff in a static method, so my dependency property
// snippet just creates a private instance method and calls it from the
// static handler.
(d as CustomMediaTransportControls).OnIsCompactOverlayButtonVisibleChanged();
}
private void OnIsCompactOverlayButtonVisibleChanged()
{
if (_compactOverlayButton != null)
{
// If the existing value is the same as the new value, this is a no-op
_compactOverlayButton.Visibility =
IsCompactOverlayButtonVisible
? Visibility.Visible
: Visibility.Collapsed;
}
}
#endregion IsCompactOverlayButtonVisible Property
I have a combobox which will load data in the data grid based on selection change.
On change of combobox selection i need to check if the current data in data grid is correct or not . if not correct i would like to cancel the combobox selection change.
here is my behavior class
public class ComboBoxSelectionBehaviour : Behavior<ComboBox>
{
public static readonly DependencyProperty SourceProperty = DependencyProperty.RegisterAttached(
"Source",
typeof(ViewModel),
typeof(ComboBoxSelectionBehaviour),
new PropertyMetadata(null));
public ViewModel Source
{
get { return (ViewModel)GetValue(SourceProperty); }
set { SetValue(SourceProperty, value); }
}
protected override void OnAttached()
{
base.OnAttached();
AssociatedObject.SelectionChanged += AssociatedObject_SelectionChanged; ;
}
protected override void OnDetaching()
{
base.OnDetaching();
AssociatedObject.SelectionChanged -= AssociatedObject_SelectionChanged;
}
private void AssociatedObject_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
var combo = sender as ComboBox;
if (Source != null)
{
// Suppress the event if errors exist
if (!Source.IsDataCorrect())
{
e.Handled = true;
}
}
}
}
even after handling the event combobox selected item is getting changed.
Please give some suggestions to solve this issue.
Could you simply just do a
myComboBox.SelectedIndex--
If the data is not correct? Or would this cause an infinite loop?
I have a TabControl with a SelectionChanged event. When the selected TabPage changes, I want to get notified for the selected TabPage if a value of one of the UIElements on the TabPage has changed.
private FrameworkElement CurrentFrameworkElement { get; set; }
public TabEvents(DispatcherEvents dispatcherEvents)
: base(dispatcherEvents)
{
EventManager.RegisterClassHandler(typeof(System.Windows.Controls.TabControl), System.Windows.Controls.TabControl.SelectionChangedEvent, new SelectionChangedEventHandler(TabControl_SelectionChanged), true);
}
private void TabControl_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (e.Source is System.Windows.Controls.TabControl)
{
var ti = ((System.Windows.Controls.TabControl)e.Source).SelectedItem as TabItem;
CurrentFrameworkElement = e.Source as System.Windows.Controls.TabControl;
}
}
With this code I can get the current TabItem. How can I detect changes of UIElement values inside the current TabItem? For example entering text in a TextBox or toggling a CheckBox should give a notification.
I found an implementation of ObservableUIElementCollection here but I don't know if I can use it for this scenario and how.
You can track your changes within the ViewModel. I have done something similar by marking a field from the property setters:
bool _hasChanged = false;
public string Name
{
get
{
return _name;
}
set
{
if (value != _name)
{
_name = value;
_hasChanged = true;
}
}
}
Then when your tab changes check the value of the _hasChanged field
I'm trying to dynamically change the background color of an editable ComboBox at runtime, using code. In particular, I want to change the background of the editable TextBox that is part of the ComboBox.
There are several answers about this on SO, like this one:
WPF change the background color of an edittable combobox in code
however, the problem is that they're all based on XAML and editing default templates. I don't want to do that, I'm searching for a generic solution that works with just code.
Is it possible? I tried the solution that seems obvious:
TextBox textBox = (TextBox)comboBox.Template.FindName("PART_EditableTextBox", comboBox);
textBox.Background = Brushes.Yellow;
But this does absolutely nothing. What am I missing?
This is how you can do it
<ComboBox Loaded="MyCombo_OnLoaded" x:Name="myCombo" IsEditable="True"></ComboBox>
private void MyCombo_OnLoaded(object sender, RoutedEventArgs e)
{
var textbox = (TextBox)myCombo.Template.FindName("PART_EditableTextBox", myCombo);
if (textbox!= null)
{
var parent = (Border)textbox.Parent;
parent.Background = Brushes.Yellow;
}
}
Reusable AttachedProperty solution for xaml only fans:
<ComboBox Background="Orange" IsEditable="True" Text="hi" local:ComboBoxHelper.EditBackground="Red"></ComboBox>
Implementation:
public static class ComboBoxHelper
{
public static readonly DependencyProperty EditBackgroundProperty = DependencyProperty.RegisterAttached(
"EditBackground", typeof (Brush), typeof (ComboBoxHelper), new PropertyMetadata(default(Brush), EditBackgroundChanged));
private static void EditBackgroundChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs args)
{
var combo = dependencyObject as ComboBox;
if (combo != null)
{
if (!combo.IsLoaded)
{
RoutedEventHandler comboOnLoaded = null;
comboOnLoaded = delegate(object sender, RoutedEventArgs eventArgs)
{
EditBackgroundChanged(dependencyObject, args);
combo.Loaded -= comboOnLoaded;
};
combo.Loaded += comboOnLoaded;
return;
}
var part = combo.Template.FindName("PART_EditableTextBox", combo);
var tb = part as TextBox;
if (tb != null)
{
var parent = tb.Parent as Border;
if (parent != null)
{
parent.Background = (Brush)args.NewValue;
}
}
}
}
[AttachedPropertyBrowsableForType(typeof(ComboBox))]
public static void SetEditBackground(DependencyObject element, Brush value)
{
element.SetValue(EditBackgroundProperty, value);
}
[AttachedPropertyBrowsableForType(typeof(ComboBox))]
public static Brush GetEditBackground(DependencyObject element)
{
return (Brush) element.GetValue(EditBackgroundProperty);
}
}
I have a requirement that I want to make a datagridcolumn which only accepts numeric values(integer) ,when the user enter something other than numbers handle the textbox .
I tried a lot of webpages ,Iam tired of these ,I greately appreciate anybody have the helping mind.
Based on #nit suggestion, you can create your own class derived from DataGridTextColumn like this:
public class DataGridNumericColumn : DataGridTextColumn
{
protected override object PrepareCellForEdit(System.Windows.FrameworkElement editingElement, System.Windows.RoutedEventArgs editingEventArgs)
{
TextBox edit = editingElement as TextBox;
edit.PreviewTextInput += OnPreviewTextInput;
return base.PrepareCellForEdit(editingElement, editingEventArgs);
}
void OnPreviewTextInput(object sender, System.Windows.Input.TextCompositionEventArgs e)
{
try
{
Convert.ToInt32(e.Text);
}
catch
{
// Show some kind of error message if you want
// Set handled to true
e.Handled = true;
}
}
}
In the PrepareCellForEdit method you register the OnPreviewTextInput method to the editing TextBox PreviewTextInput event, where you validate for numeric values.
In xaml, you simply use it:
<DataGrid ItemsSource="{Binding SomeCollection}">
<DataGrid.Columns>
<DataGridTextColumn Binding="{Binding NonNumericProperty}"/>
<local:DataGridNumericColumn Binding="{Binding NumericProperty}"/>
</DataGrid.Columns>
</DataGrid>
Hope this helps
Use TryParse instead, this helps to restrict input values to integer numbers only.
/// <summary>
/// This class help to create data grid cell which only support interger numbers.
/// </summary>
public class DataGridNumericColumn : DataGridTextColumn
{
protected override object PrepareCellForEdit(FrameworkElement editingElement, RoutedEventArgs editingEventArgs)
{
TextBox edit = editingElement as TextBox;
if (edit != null) edit.PreviewTextInput += OnPreviewTextInput;
return base.PrepareCellForEdit(editingElement, editingEventArgs);
}
private void OnPreviewTextInput(object sender, System.Windows.Input.TextCompositionEventArgs e)
{
int value;
if (!int.TryParse(e.Text, out value))
e.Handled = true;
}
}
If you dont want to show any validation errors and just want to block any non-numeral value then you can create the DataGridTemplateColumn and in CellEditingTemplate use the TextBox.
<DataGridTemplateColumn Width="100*">
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<TextBlock Text="{Binding Path=NumericProperty}"/>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
<DataGridTemplateColumn.CellEditingTemplate>
<DataTemplate>
<TextBox PreviewTextInput="TextBox_PreviewTextInput" Text="{Binding Path=NumericProperty}"/>
</DataTemplate>
</DataGridTemplateColumn.CellEditingTemplate>
</DataGridTemplateColumn>
and in PreviewTextInput of the TextBox set e.Handled = true if value is other than integer:
private void TextBox_PreviewTextInput(object sender, TextCompositionEventArgs e)
{
try
{
Convert.ToInt32(e.Text);
}
catch
{
e.Handled = true;
}
}
I got here looking for a solution to the same problem: constraining the input into cells on a DataGrid to be numeric. But the accepted answer did not work for me. The following did:
For the DataGrid add an event handler for PreparingForCellEdit.
In that event handler, cast the EditingElement to a TextBox and add an event handler for PreviewTextInput to the TextBox.
In the PreviewTextInput event handler set e.Handled to true, if the input should not be allowed.
The above steps work if the user clicks the cell to edit. However, if the cell is not in edit mode, the PreparingForCellEdit event will not be called. To perform validation in that case:
Add an event handler to the DataGrid for PreviewTextInput.
In that event handler, safely cast e.OriginalSource to a DataGridCell (exiting, if it is not a DataGridCell), check the DataGridCell's IsEditing property, and if the cell is not editing set e.Handled to true.
The effect of the above is that the user will have to click into the cell in order to edit its contents and, as such, the PreparingForCellEdit / PreviewTextInput combination above will be invoked for all changes to the cell's contents.
Just to extend #Omribitan's answer, Here is the solution with a data Paste guard added:
public class NumericTextColumn : DataGridTextColumn
{
protected override object PrepareCellForEdit(FrameworkElement editingElement, RoutedEventArgs editingEventArgs)
{
var edit = editingElement as TextBox;
edit.PreviewTextInput += Edit_PreviewTextInput;
DataObject.AddPastingHandler(edit, OnPaste);
return base.PrepareCellForEdit(editingElement, editingEventArgs);
}
private void OnPaste(object sender, DataObjectPastingEventArgs e)
{
var data = e.SourceDataObject.GetData(DataFormats.Text);
if (!IsDataValid(data)) e.CancelCommand();
}
private void Edit_PreviewTextInput(object sender, TextCompositionEventArgs e)
{
e.Handled = !IsDataValid(e.Text);
}
bool IsDataValid(object data)
{
try
{
Convert.ToInt32(data);
return true;
}
catch
{
return false;
}
}
}
For whatever it's worth, here's how I solved it. This solution allows you to specify a variety of options when validating input, allows string formatting to be used (e.g. '$15.00' in the data grid) and more.
The null value and string formatting provided by the Binding class itself do not suffice as neither act correctly when the cell is editable so this class covers it. What this does is it uses another class that I've been using for a long time already: TextBoxInputBehavior, it has been an invaluable asset for me and it originally came from WPF – TextBox Input Behavior blog post albeit the version here seems much older (but well tested). So what I did I just transferred this existing functionality I already had on my TextBoxes to the my custom column and thus I have the same behaviour in both. Isn't that neat?
Here's the code of the custom column:
public class DataGridNumberColumn : DataGridTextColumn
{
private TextBoxInputBehavior _behavior;
protected override FrameworkElement GenerateElement(DataGridCell cell, object dataItem)
{
var element = base.GenerateElement(cell, dataItem);
// A clever workaround the StringFormat issue with the Binding set to the 'Binding' property. If you use StringFormat it
// will only work in edit mode if you changed the value, otherwise it will retain formatting when you enter editing.
if (!string.IsNullOrEmpty(StringFormat))
{
BindingOperations.ClearBinding(element, TextBlock.TextProperty);
BindingOperations.SetBinding(element, FrameworkElement.TagProperty, Binding);
BindingOperations.SetBinding(element,
TextBlock.TextProperty,
new Binding
{
Source = element,
Path = new PropertyPath("Tag"),
StringFormat = StringFormat
});
}
return element;
}
protected override object PrepareCellForEdit(FrameworkElement editingElement, RoutedEventArgs editingEventArgs)
{
if (!(editingElement is TextBox textBox))
return null;
var originalText = textBox.Text;
_behavior = new TextBoxInputBehavior
{
IsNumeric = true,
EmptyValue = EmptyValue,
IsInteger = IsInteger
};
_behavior.Attach(textBox);
textBox.Focus();
if (editingEventArgs is TextCompositionEventArgs compositionArgs) // User has activated editing by already typing something
{
if (compositionArgs.Text == "\b") // Backspace, it should 'clear' the cell
{
textBox.Text = EmptyValue;
textBox.SelectAll();
return originalText;
}
if (_behavior.ValidateText(compositionArgs.Text))
{
textBox.Text = compositionArgs.Text;
textBox.Select(textBox.Text.Length, 0);
return originalText;
}
}
if (!(editingEventArgs is MouseButtonEventArgs) || !PlaceCaretOnTextBox(textBox, Mouse.GetPosition(textBox)))
textBox.SelectAll();
return originalText;
}
private static bool PlaceCaretOnTextBox(TextBox textBox, Point position)
{
int characterIndexFromPoint = textBox.GetCharacterIndexFromPoint(position, false);
if (characterIndexFromPoint < 0)
return false;
textBox.Select(characterIndexFromPoint, 0);
return true;
}
protected override void CancelCellEdit(FrameworkElement editingElement, object uneditedValue)
{
UnwireTextBox();
base.CancelCellEdit(editingElement, uneditedValue);
}
protected override bool CommitCellEdit(FrameworkElement editingElement)
{
UnwireTextBox();
return base.CommitCellEdit(editingElement);
}
private void UnwireTextBox() => _behavior.Detach();
public static readonly DependencyProperty EmptyValueProperty = DependencyProperty.Register(
nameof(EmptyValue),
typeof(string),
typeof(DataGridNumberColumn));
public string EmptyValue
{
get => (string)GetValue(EmptyValueProperty);
set => SetValue(EmptyValueProperty, value);
}
public static readonly DependencyProperty IsIntegerProperty = DependencyProperty.Register(
nameof(IsInteger),
typeof(bool),
typeof(DataGridNumberColumn));
public bool IsInteger
{
get => (bool)GetValue(IsIntegerProperty);
set => SetValue(IsIntegerProperty, value);
}
public static readonly DependencyProperty StringFormatProperty = DependencyProperty.Register(
nameof(StringFormat),
typeof(string),
typeof(DataGridNumberColumn));
public string StringFormat
{
get => (string) GetValue(StringFormatProperty);
set => SetValue(StringFormatProperty, value);
}
}
What I did is I peeked into the source code of DataGridTextColumn and handled the TextBox creation in almost the same way plus I attached the custom behaviour to the TextBox.
Here's the code of the behavior I attached (this is a behavior you can use on any TextBox):
public class TextBoxInputBehavior : Behavior<TextBox>
{
#region DependencyProperties
public static readonly DependencyProperty RegularExpressionProperty = DependencyProperty.Register(
nameof(RegularExpression),
typeof(string),
typeof(TextBoxInputBehavior),
new FrameworkPropertyMetadata(".*"));
public string RegularExpression
{
get
{
if (IsInteger)
return #"^[0-9\-]+$";
if (IsNumeric)
return #"^[0-9.\-]+$";
return (string)GetValue(RegularExpressionProperty);
}
set { SetValue(RegularExpressionProperty, value); }
}
public static readonly DependencyProperty MaxLengthProperty = DependencyProperty.Register(
nameof(MaxLength),
typeof(int),
typeof(TextBoxInputBehavior),
new FrameworkPropertyMetadata(int.MinValue));
public int MaxLength
{
get { return (int)GetValue(MaxLengthProperty); }
set { SetValue(MaxLengthProperty, value); }
}
public static readonly DependencyProperty EmptyValueProperty = DependencyProperty.Register(
nameof(EmptyValue),
typeof(string),
typeof(TextBoxInputBehavior));
public string EmptyValue
{
get { return (string)GetValue(EmptyValueProperty); }
set { SetValue(EmptyValueProperty, value); }
}
public static readonly DependencyProperty IsNumericProperty = DependencyProperty.Register(
nameof(IsNumeric),
typeof(bool),
typeof(TextBoxInputBehavior));
public bool IsNumeric
{
get { return (bool)GetValue(IsNumericProperty); }
set { SetValue(IsNumericProperty, value); }
}
public static readonly DependencyProperty IsIntegerProperty = DependencyProperty.Register(
nameof(IsInteger),
typeof(bool),
typeof(TextBoxInputBehavior));
public bool IsInteger
{
get { return (bool)GetValue(IsIntegerProperty); }
set
{
if (value)
SetValue(IsNumericProperty, true);
SetValue(IsIntegerProperty, value);
}
}
public static readonly DependencyProperty AllowSpaceProperty = DependencyProperty.Register(
nameof(AllowSpace),
typeof (bool),
typeof (TextBoxInputBehavior));
public bool AllowSpace
{
get { return (bool) GetValue(AllowSpaceProperty); }
set { SetValue(AllowSpaceProperty, value); }
}
#endregion
protected override void OnAttached()
{
base.OnAttached();
AssociatedObject.PreviewTextInput += PreviewTextInputHandler;
AssociatedObject.PreviewKeyDown += PreviewKeyDownHandler;
DataObject.AddPastingHandler(AssociatedObject, PastingHandler);
}
protected override void OnDetaching()
{
base.OnDetaching();
if (AssociatedObject == null)
return;
AssociatedObject.PreviewTextInput -= PreviewTextInputHandler;
AssociatedObject.PreviewKeyDown -= PreviewKeyDownHandler;
DataObject.RemovePastingHandler(AssociatedObject, PastingHandler);
}
private void PreviewTextInputHandler(object sender, TextCompositionEventArgs e)
{
string text;
if (AssociatedObject.Text.Length < AssociatedObject.CaretIndex)
text = AssociatedObject.Text;
else
text = TreatSelectedText(out var remainingTextAfterRemoveSelection)
? remainingTextAfterRemoveSelection.Insert(AssociatedObject.SelectionStart, e.Text)
: AssociatedObject.Text.Insert(AssociatedObject.CaretIndex, e.Text);
e.Handled = !ValidateText(text);
}
private void PreviewKeyDownHandler(object sender, KeyEventArgs e)
{
if (e.Key == Key.Space)
e.Handled = !AllowSpace;
if (string.IsNullOrEmpty(EmptyValue))
return;
string text = null;
// Handle the Backspace key
if (e.Key == Key.Back)
{
if (!TreatSelectedText(out text))
{
if (AssociatedObject.SelectionStart > 0)
text = AssociatedObject.Text.Remove(AssociatedObject.SelectionStart - 1, 1);
}
}
// Handle the Delete key
else if (e.Key == Key.Delete)
{
// If text was selected, delete it
if (!TreatSelectedText(out text) && AssociatedObject.Text.Length > AssociatedObject.SelectionStart)
{
// Otherwise delete next symbol
text = AssociatedObject.Text.Remove(AssociatedObject.SelectionStart, 1);
}
}
if (text == string.Empty)
{
AssociatedObject.Text = EmptyValue;
if (e.Key == Key.Back)
AssociatedObject.SelectionStart++;
e.Handled = true;
}
}
private void PastingHandler(object sender, DataObjectPastingEventArgs e)
{
if (e.DataObject.GetDataPresent(DataFormats.Text))
{
var text = Convert.ToString(e.DataObject.GetData(DataFormats.Text));
if (!ValidateText(text))
e.CancelCommand();
}
else
e.CancelCommand();
}
public bool ValidateText(string text)
{
return new Regex(RegularExpression, RegexOptions.IgnoreCase).IsMatch(text) && (MaxLength == int.MinValue || text.Length <= MaxLength);
}
/// <summary>
/// Handle text selection.
/// </summary>
/// <returns>true if the character was successfully removed; otherwise, false.</returns>
private bool TreatSelectedText(out string text)
{
text = null;
if (AssociatedObject.SelectionLength <= 0)
return false;
var length = AssociatedObject.Text.Length;
if (AssociatedObject.SelectionStart >= length)
return true;
if (AssociatedObject.SelectionStart + AssociatedObject.SelectionLength >= length)
AssociatedObject.SelectionLength = length - AssociatedObject.SelectionStart;
text = AssociatedObject.Text.Remove(AssociatedObject.SelectionStart, AssociatedObject.SelectionLength);
return true;
}
}
All the good credit for above Behaviour class goes to blindmeis, I merely tweaked it over time. After checking his Blog I see he has a newer version of it so you may check it out. I was very happy to find out I could use his behaviour on DataGrid as well!
This solution worked really well, you can edit the cell properly via mouse/keyboard, paste the contents properly, use any binding source update triggers, use any string formatting etc. - it just works.
Here's an example of how to use it:
<local:DataGridNumberColumn Header="Nullable Int Currency" IsInteger="True" Binding="{Binding IntegerNullable, TargetNullValue=''}" StringFormat="{}{0:C}" />
Hope this helps someone.
I went on from Omris approach
however i wanted to be able to delete the cell value after it has input in case they wanted to clear it
The way i did this was overriding the CommitCellEdit method and making the string null instead of blank. Im also using decimal? in my case
public class DataGridNumericColumn : DataGridTextColumn
{
protected override object PrepareCellForEdit(System.Windows.FrameworkElement editingElement, System.Windows.RoutedEventArgs editingEventArgs)
{
TextBox edit = editingElement as TextBox;
edit.PreviewTextInput += OnPreviewTextInput;
return base.PrepareCellForEdit(editingElement, editingEventArgs);
}
protected override bool CommitCellEdit(System.Windows.FrameworkElement editingElement)
{
TextBox tb = editingElement as TextBox;
if (string.IsNullOrEmpty(tb.Text))
tb.Text = null;
return base.CommitCellEdit(editingElement);
}
void OnPreviewTextInput(object sender, System.Windows.Input.TextCompositionEventArgs e)
{
try
{
Convert.ToDecimal(e.Text);
}
catch
{
// Show some kind of error message if you want
// Set handled to true
e.Handled = true;
}
}
}