Wie setzen maxlength für die combobox-Komponente in WPF?

Wie kann ich einstellen, maxlength, combobox, die mit einem Stil versehen.

Dank

InformationsquelleAutor der Frage Ershad | 2009-10-15

Bei der Verwendung von DependencyProperty, können wir die maxlength der combo-box ohne änderung Ihrer style/template.

public class EditableComboBox
{

    public static int GetMaxLength(DependencyObject obj)
    {
        return (int)obj.GetValue(MaxLengthProperty);
    }

    public static void SetMaxLength(DependencyObject obj, int value)
    {
        obj.SetValue(MaxLengthProperty, value);
    }

    //Using a DependencyProperty as the backing store for MaxLength.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty MaxLengthProperty = DependencyProperty.RegisterAttached("MaxLength", typeof(int), typeof(EditableComboBox), new UIPropertyMetadata(OnMaxLenghtChanged));

    private static void OnMaxLenghtChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
    {
        var comboBox = obj as ComboBox;
        if (comboBox == null) return;

        comboBox.Loaded +=
            (s, e) =>
            {
                var textBox = comboBox.FindChild(typeof(TextBox), "PART_EditableTextBox");
                if (textBox == null) return;

                textBox.SetValue(TextBox.MaxLengthProperty, args.NewValue);
            };
    }
}

Beispiel:

<ComboBox ComboboxHelper:EditableComboBox.MaxLength="50" />

Wo ComboboxHelper ist:

xmlns:ComboboxHelper="clr-namespace:yourNameSpace;assembly=yourAssembly"

comboBox.FindChild(...) Methode ist gebucht hier.

InformationsquelleAutor der Antwort Tri Q Tran

Oder verwenden Sie den GotFocus -, oder Loaded-Ereignis der combobox für die Einstellung der maxlength.Wenn die maxlength tust viel ändern während der Laufzeit, die Sie verwenden können, loaded-Ereignis oder sonst mit gotfocus-Ereignis

<ComboBox Height="30" IsEditable="True" Loaded="ComboBox_Loaded"/>

und in der jeweiligen Veranstaltung...

   var obj = (ComboBox)sender;
    if (obj != null)
    {
        var myTextBox = (TextBox)obj.Template.FindName("PART_EditableTextBox",obj);
        if (myTextBox != null)
        {
            myTextBox.MaxLength = maxLength;
        }
    }

InformationsquelleAutor der Antwort biju

Sind Sie richtig. Es ist ein maxlength für ein Textfeld, aber nicht für eine combobox. Du musst Rollen Sie Ihre eigenen mit einer Textbox als Vermittler. Hier einige code:

public int MaxLength {get; set;}
protected override void OnGotFocus(System.Windows.RoutedEventArgs e)
{
    base.OnGotFocus(e);
    TextBox thisTextBox = (TextBox)base.GetTemplateChild("PART_EditableTextBox");
    if (thisTextBox != null)
        thisTextBox.MaxLength = MaxLength;
}

InformationsquelleAutor der Antwort Rap

Diese TextBox kommt null.
Den Stil gegeben, ist wie folgt.

<ControlTemplate x:Key="ComboBoxToggleButton" TargetType="ToggleButton">
        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*" />
                <ColumnDefinition Width="{Binding Path=(local:ToggleComboBox.Width),
                     RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ComboBox}}}" />
            </Grid.ColumnDefinitions>
            <Border x:Name="Border" 
                    Grid.Column="1"
                    CornerRadius="2"
                    Background="#CCFFCC"
                    BorderBrush="#000080"
                    BorderThickness="4" />

            <Border Grid.Column="0"
                    CornerRadius="8,8,8,8" 
                    Margin="0" 
                    Background="#CCFFCC" 
                    BorderBrush="#000080"
                    BorderThickness="4,4,4,4" />

            <Image x:Name="Arrow"
                   Grid.Column="1"     
                   Source="Arrow.png" Margin="4,4,4,4"
                   HorizontalAlignment="Center"
                   VerticalAlignment="Center"/>
        </Grid>
        <ControlTemplate.Triggers>
            <Trigger Property="ToggleButton.IsMouseOver" Value="true">
                <Setter TargetName="Border" Property="Background" Value="{StaticResource DarkBrush}" />
            </Trigger>
            <Trigger Property="ToggleButton.IsChecked" Value="true">
                <Setter TargetName="Border" Property="Background" Value="{StaticResource PressedBrush}" />
            </Trigger>
            <Trigger Property="IsEnabled" Value="False">
                <Setter TargetName="Border" Property="Background" Value="{StaticResource DisabledBackgroundBrush}" />
                <Setter TargetName="Border" Property="BorderBrush" Value="{StaticResource DisabledBorderBrush}" />
                <Setter Property="Foreground" Value="{StaticResource DisabledForegroundBrush}"/>
                <!--<Setter TargetName="Arrow" Property="Fill" Value="{StaticResource DisabledForegroundBrush}" />-->
            </Trigger>
        </ControlTemplate.Triggers>
    </ControlTemplate>

    <ControlTemplate x:Key="ComboBoxTextBox" TargetType="TextBox">
        <Border x:Name="PART_ContentHost" Focusable="False" Background="{TemplateBinding Background}" />
    </ControlTemplate>


    <Style x:Key="ComboBoxStyle" TargetType="ComboBox">
        <Setter Property="SnapsToDevicePixels" Value="true"/>
        <Setter Property="OverridesDefaultStyle" Value="true"/>
        <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto"/>
        <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto"/>
        <Setter Property="ScrollViewer.CanContentScroll" Value="true"/>
        <Setter Property="MinWidth" Value="120"/>
        <Setter Property="MinHeight" Value="20"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="ComboBox">
                    <Grid>
                        <ToggleButton Name="ToggleButton" 
                                      Template="{StaticResource ComboBoxToggleButton}" 
                                      Grid.Column="2" 
                                      Focusable="false"
                                      IsChecked="{Binding Path=IsDropDownOpen,
                                                          Mode=TwoWay,
                                                          RelativeSource={RelativeSource TemplatedParent}}"
                                      ClickMode="Press"/>

                        <ContentPresenter Name="ContentSite"
                                          IsHitTestVisible="False" 
                                          Content="{TemplateBinding SelectionBoxItem}"
                                          ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}"
                                          ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}"
                                          Margin="9,2,28,2"
                                          VerticalAlignment="Center"
                                          HorizontalAlignment="Left" />

                        <TextBox x:Name="PART_EditableTextBox"
                                 Style="{x:Null}" 
                                 Template="{StaticResource ComboBoxTextBox}" 
                                 HorizontalAlignment="Left" 
                                 VerticalAlignment="Center" 
                                 Margin="3,3,23,3"
                                 Focusable="True" 
                                 Background="Transparent"
                                 Visibility="Hidden"
                                 IsReadOnly="{TemplateBinding IsReadOnly}"/>

                        <Popup Name="Popup"
                               Placement="Bottom"
                               IsOpen="{TemplateBinding IsDropDownOpen}"
                               AllowsTransparency="True" 
                               Focusable="False"
                               PopupAnimation="Slide">

                            <Grid Name="DropDown"
                                  SnapsToDevicePixels="True"             
                                  MinWidth="{TemplateBinding ActualWidth}"
                                  MaxHeight="{TemplateBinding MaxDropDownHeight}">

                                <Border x:Name="DropDownBorder"
                                        Background="#CCFFCC" 
                                        BorderBrush="#000080"
                                        BorderThickness="2"/>

                                <ScrollViewer Margin="4,6,4,6" SnapsToDevicePixels="True">
                                    <ScrollViewer.Resources>
                                        <sys:Double x:Key="{x:Static SystemParameters.VerticalScrollBarWidthKey}">25</sys:Double>
                                    </ScrollViewer.Resources>                                    
                                    <StackPanel IsItemsHost="True" />
                                </ScrollViewer>
                            </Grid>
                        </Popup>
                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="HasItems" Value="false">
                            <Setter TargetName="DropDownBorder" Property="MinHeight" Value="95"/>
                        </Trigger>
                        <Trigger Property="IsEnabled" Value="false">
                            <Setter Property="Foreground" Value="{StaticResource DisabledForegroundBrush}"/>
                        </Trigger>
                        <Trigger Property="IsGrouping" Value="true">
                            <Setter Property="ScrollViewer.CanContentScroll" Value="false"/>
                        </Trigger>
                        <Trigger SourceName="Popup" Property="Popup.AllowsTransparency" Value="true">
                            <Setter TargetName="DropDownBorder" Property="CornerRadius" Value="4"/>
                            <Setter TargetName="DropDownBorder" Property="Margin" Value="0,2,0,0"/>
                        </Trigger>
                        <Trigger Property="IsEditable" Value="true">
                            <Setter Property="IsTabStop" Value="false"/>
                            <Setter TargetName="PART_EditableTextBox" Property="Visibility" Value="Visible"/>
                            <Setter TargetName="ContentSite" Property="Visibility" Value="Hidden"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
        <Setter Property="ItemContainerStyle" >
            <Setter.Value>
                <Style TargetType="{x:Type ComboBoxItem}">
                    <Setter Property="FontSize" Value="20" />
                </Style>
            </Setter.Value>
        </Setter>
    </Style>

InformationsquelleAutor der Antwort Ershad

-1

Ich verwendet, PreviewKeyDown-event, sehr einfache + Sie können die Warnung zeigen oder so etwas.

Registrieren Sie die Methode unten, um Ihre ComboBox.PreviewKeyDown += event

KeyDown-Ereignis wird nicht ausgelöst, wenn der Benutzer die Leertaste drücken.

private void ComboBox_PreviewKeyDown(object sender, KeyEventArgs e)
{
    if (ComboBox.Text.Length > 19) //allow max 20 chars
    {
        if (e.Key != Key.Back) //allow removing chars
        {
            e.Handled = true; //block any additional key press if there is more than allowed max
            System.Media.SystemSounds.Beep.Play(); //optional: beep to let user know he is out of space :)
        }
    }
}

InformationsquelleAutor der Antwort Mr. Noob

-1

Ich gefunden, einfache Lösung über XAML. In der comboBox Ressourcen, die wir-set-Stil für Textfeld und über setter gesetzt maxlenth.
```
<ComboBox Name="comboBox" Width="100" IsEditable="True">
<ComboBox.Resources>
<Style TargetType="{x:Type TextBox}"> 
    <Setter Property="MaxLength" Value="yourValue"></Setter> 
</Style>
</ComboBox.Resources>
</ComboBox>
```
EDIT: Das funktioniert mit Actipro ComboBox. Für die üblichen comboBox um diese Arbeit zu machen, schauen Sie hier

InformationsquelleAutor der Antwort Sasha

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