WPF find textbox control inside combo box with combobox.Template

Question

This question is extension to WPF ComboBox with checkboxes and textbox with search field

Adding the UserControl in my window as follows

<Usercontrols:MultiSelectComboBox x:Name="multiCombo" HorizontalAlignment="Left" Height="28" VerticalAlignment="Top" Width="235" Margin="81,27,0,0"/>

I am having my combobox.Template as follows in my combobox

<ComboBox>
<ComboBox.Template>
        <ControlTemplate TargetType="ComboBox">
            <Grid Name="control" >

                <ToggleButton 
                    x:Name="ToggleButton" 
                   Grid.Column="2" IsChecked="{Binding Path=IsDropDownOpen,Mode=TwoWay,RelativeSource={RelativeSource TemplatedParent}}"
                    Focusable="false"                           
                    ClickMode="Press" HorizontalContentAlignment="Left" >
                    <ToggleButton.Template>
                        <ControlTemplate>
                            <Grid>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="*"/>
                                    <ColumnDefinition Width="18"/>
                                </Grid.ColumnDefinitions>
                                <Border
              x:Name="Border" 
              Grid.ColumnSpan="2"
              CornerRadius="2"
              Background="White"
              BorderBrush="Silver"
              BorderThickness="1,1,1,1" />
                                <Border 
                x:Name="BorderComp" 
              Grid.Column="0"
              CornerRadius="2" 
              Margin="1" 
             Background="White"
              BorderBrush="Black"
              BorderThickness="0,0,0,0" >
                                    <TextBlock Text="{Binding Path=Text,RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl}}" 
                                           Background="White" Padding="3" />
                                </Border>
                                <Path 
              x:Name="Arrow"
              Grid.Column="1"     
              Fill="Black"
              HorizontalAlignment="Center"
              VerticalAlignment="Center"
              Data="M 0 0 L 4 4 L 8 0 Z"/>
                            </Grid>
                        </ControlTemplate>
                    </ToggleButton.Template>
                </ToggleButton>
                <Popup 
Name="Popup"
Placement="Bottom"                        
AllowsTransparency="True" 
Focusable="False"  IsOpen="{TemplateBinding IsDropDownOpen}"
PopupAnimation="Slide">
                    <Grid 
    Name="DropDown"
    SnapsToDevicePixels="True"  
    MinWidth="{TemplateBinding ActualWidth}"
    MaxHeight="{TemplateBinding MaxDropDownHeight}">
                        <Border 
        x:Name="DropDownBorder"
        BorderThickness="1" Background="White"
        BorderBrush="Black"/>
                        <ScrollViewer Margin="4,6,4,6" SnapsToDevicePixels="True" DataContext="{Binding}">
                            <Grid>
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="Auto" />
                                    <RowDefinition Height="*" />
                                </Grid.RowDefinitions>
                                <TextBox Name="TextBox"  Text="{Binding Path=Text, Mode=TwoWay}" TextChanged="TextBox_TextChanged" />
                                <StackPanel Grid.Row="2" IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Contained" />
                            </Grid>
                        </ScrollViewer>
                    </Grid>
                </Popup>
            </Grid>
            <ControlTemplate.Triggers>
                <Trigger Property="HasItems" Value="false">
                    <Setter TargetName="DropDownBorder" Property="MinHeight" Value="95"/>
                </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>
            </ControlTemplate.Triggers>
        </ControlTemplate>
    </ComboBox.Template>
</ComboBox>

I am trying to find the TextBox control inside UserControl with ComboBox and ComboBox.ItemTemplate on my text box changed event. I tried as below but i am getting null

private void multiCombo_TextChange(object sender, EventArgs e)
    {
        Grid TxtBox = (Grid)multiCombo.Template.FindName("control", multiCombo);
        //TextBox textBox = sender as TextBox;
        MessageBox.Show(TxtBox.ToString());
    }

There is no TextBox control created until the Popup is opened. Where is the multiCombo_TextChange event handler hooked up? — mm8, Aug 14 '18 at 13:12
Ok but once after opening the popup I will enter some text in the text box based on that it should filter which I can write — Learner, Aug 14 '18 at 13:13

mm8 · Accepted Answer · 2018-08-14T13:24:37.390

2

You could cast the OriginalSource property of the TextChangedEventArgs:

private void multiCombo_TextChange(object sender, TextChangedEventArgs e)
{
    TextBox textBox = e.OriginalSource as TextBox;
    //...
}

edited Aug 14 '18 at 13:24

answered Aug 14 '18 at 13:14

mm8

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sender I am getting as comobox – Learner Aug 14 '18 at 13:17
`+ sender {WpfApp1.usercontrol.MultiSelectComboBox} object {WpfApp1.usercontrol.MultiSelectComboBox} ` – Learner Aug 14 '18 at 13:18
Here is my code https://drive.google.com/file/d/1VjIkceNVfbis109074ERlYO2R2Q4Die1/view?usp=sharing – Learner Aug 14 '18 at 13:22
See my edit. You should be able to cast the OriginalSource of the TextChangedEventArgs. – mm8 Aug 14 '18 at 13:25
Thanks in the user control I have written the event as follows `private void TextBox_TextChanged(object sender, TextChangedEventArgs e) { //MessageBox.Show("hi"); TextBox textBox = e.OriginalSource as TextBox; this.TextBoxClick(textBox, e); }` – Learner Aug 14 '18 at 13:29

WPF find textbox control inside combo box with combobox.Template

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