DataGridTextColumn.MaxLength?

Question

How to set MaxLength property for DataGridTextColumn?

Answer 1

<tk:DataGridTextColumn Binding="{Binding Text}"> <tk:DataGridTextColumn.EditingElementStyle> <Style TargetType="TextBox"> <Setter Property="MaxLength" Value="16"/> </Style> </tk:DataGridTextColumn.EditingElementStyle> </tk:DataGridTextColumn> 

You can also set it using the following behavior, so you don't need to use style and setters every time:

 Public Class TextBoxBehavior Private Shared Types As Type() = New Type() {GetType(AutoCompleteBox), GetType(ComboBox), GetType(DataGridTextColumn)} Public Shared Function GetMaxLength(ByVal element As DependencyObject) As Integer Return element.GetValue(MaxLengthProperty) End Function Public Shared Sub SetMaxLength(ByVal element As DependencyObject, ByVal value As Integer) element.SetValue(MaxLengthProperty, value) End Sub Private Shared Sub ValidateElement(ByVal element As DependencyObject) If element Is Nothing Then Throw New ArgumentNullException("element") If Not Types.Contains(element.GetType) Then Throw New NotSupportedException("The TextBoxBehavior is not supported for the given element") End Sub Public Shared ReadOnly MaxLengthProperty As DependencyProperty = DependencyProperty.RegisterAttached("MaxLength", GetType(Integer), GetType(TextBoxBehavior), New FrameworkPropertyMetadata(Integer.MaxValue, AddressOf TextBox_MaxLengthChanged)) Private Shared Sub TextBox_MaxLengthChanged(ByVal sender As Object, ByVal e As DependencyPropertyChangedEventArgs) If sender Is Nothing Then Exit Sub Dim value = DirectCast(e.NewValue, Integer) If TypeOf sender Is AutoCompleteBox Then Dim acb = DirectCast(sender, AutoCompleteBox) If acb.IsLoaded Then Dim tb = DirectCast(acb.Template.FindName("Text", acb), TextBox) tb.MaxLength = value Else acb.AddHandler(AutoCompleteBox.LoadedEvent, New RoutedEventHandler(AddressOf Element_Loaded)) End If ElseIf TypeOf sender Is ComboBox Then Dim cb = DirectCast(sender, ComboBox) If cb.IsLoaded Then Dim tb = DirectCast(cb.Template.FindName("PART_EditableTextBox", cb), TextBox) tb.MaxLength = value Else cb.AddHandler(ComboBox.LoadedEvent, New RoutedEventHandler(AddressOf Element_Loaded)) End If ElseIf TypeOf sender Is DataGridTextColumn Then Dim dgtc = DirectCast(sender, DataGridTextColumn) Dim setter = GetIsMaxLengthSet(dgtc.EditingElementStyle) If setter Is Nothing Then Dim style = New Style(GetType(TextBox), dgtc.EditingElementStyle) style.Setters.Add(New Setter(TextBox.MaxLengthProperty, value)) dgtc.EditingElementStyle = style style.Seal() Else setter.Value = value End If End If End Sub Private Shared Function GetIsMaxLengthSet(ByVal style As Style) As Setter If style Is Nothing Then Return Nothing Dim setter = style.Setters.LastOrDefault(Function(s) TypeOf s Is Setter AndAlso DirectCast(s, Setter).Property Is TextBox.MaxLengthProperty) If setter IsNot Nothing Then Return setter Else Return GetIsMaxLengthSet(style.BasedOn) End Function Private Shared Sub Element_Loaded(ByVal sender As Object, ByVal e As RoutedEventArgs) Dim ml = GetMaxLength(sender) TextBox_MaxLengthChanged(sender, New DependencyPropertyChangedEventArgs(TextBox.MaxLengthProperty, -1, ml)) sender.RemoveHandler(FrameworkElement.LoadedEvent, New RoutedEventHandler(AddressOf Element_Loaded)) End Sub End Class 

Using:

 <ComboBox xmlns:loc="MyNamesapace" loc:TextBoxBehavior.MaxLength="50" /> 

Answer 2

If you have a common style among all the columns, and you want to add an additional style to one or more of them, you can use the Style.BasedOn property:

  <DataGridTextColumn Binding="{Binding SomeProperty, UpdateSourceTrigger=PropertyChanged}" ElementStyle="{StaticResource CellErrorStyle}"> <DataGridTextColumn.EditingElementStyle> <Style TargetType="TextBox" BasedOn="{StaticResource OriginalStyleKey}"> <Setter Property="MaxLength" Value="5" /> </Style> </DataGridTextColumn.EditingElementStyle> </DataGridTextColumn>