Wpf - find a control in headertemplate and edit it

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Hello,
I can find a control in DataGridTemplateColumn declared in main resource

XML

<DataGridTemplateColumn x:Key="rowRegroupement"  MinWidth="140" Width="1*">
    <DataGridTemplateColumn.HeaderTemplate>
        <DataTemplate>
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition />
                    <RowDefinition />
                    <RowDefinition />
                </Grid.RowDefinitions>
                <Label x:Name="lblRegLib" Grid.Row="0" Content="{x:Static resx:resTabBord.lblAchatsBud}"/>
                <Rectangle Grid.Row="1" Fill="{StaticResource scbGrey2}" Margin="-7, 2" Height="1.5" />
                <TextBox x:Name="txtRegLib" Grid.Row="2" Margin="2" Height="24" Visibility="{Binding ElementName=ucTabBord, Path=ModeAff, Converter={StaticResource BoolToVisibility}, ConverterParameter=true}"/>
            </Grid>
        </DataTemplate>
    </DataGridTemplateColumn.HeaderTemplate>

Like this:

C#

var colModel = (DataGridTemplateColumn)this.Resources["rowRegroupement"];
var tpl = colModel.HeaderTemplate.LoadContent(); // Instanciation du template pour pouvoir parcourir ses controls
var ctrls = Classes.clsUtils.FindVisualChildren<Label>(tpl);
foreach (var ctrl in ctrls) {
    ((Label)ctrl).Content = "TEST"; // KO
}

But if i want change a property (content by example), the change don't occurs.
I thing it's because the template is loaded with LoadContent().
But if i don't made this, i can't find a control inside template.

Do you have a solution ?

What I have tried:

C#

//ucDataGridColHead uc = ((ucDataGridColHead)ctrl);
//uc.Title = Col.BddNomTable; // Ne fonctionne pas car les controls sont déjà mappés avec LoadContent().
//var lblTitre = uc.FindName("lblTitre");
//if (lblTitre != null) { ((System.Windows.Documents.Run)lblTitre).Text = Col.BddNomTable; } // Ne fonctionne pas car les controls sont déjà mappés avec LoadContent().

Posted 6-Dec-16 0:35am

Member 12521151

Updated 7-Dec-16 2:11am

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Richard Deeming · Accepted Answer · 2016-12-06T06:19:00

A DataTemplate defines a template for a group of controls.

When you call LoadContent, you create an instance of the control tree defined within the template. Your code then modifies that single instance, and then throws it away.

The next time something uses the DataTemplate to create an instance of the control tree, your changes are not there, because you changed an instance of the control tree, not the template itself.

You might be able to drill into the colModel.HeaderTemplate.VisualTree to find and modify the element, assuming the template isn't sealed by the time you get to it. Or, you might be able to create the template through code - but that's a lot more complicated than doing it through XAML.

The best option is to find another way to make the changes you need.

Pete O'Hanlon · Accepted Answer · 2016-12-07T02:11:00

This is something you should be able to achieve pretty much entirely in XAML. Basically, you're going to want to put a ContentPresenter in the place of the Label and composite a Label as the default content in there. Then, you're just going to switch the Content depending on a trigger condition inside the DataTemplate.

XML

<DataGridTemplateColumn x:Key="rowRegroupement"  MinWidth="140" Width="1*">
    <DataGridTemplateColumn.HeaderTemplate>
        <DataTemplate>
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition />
                    <RowDefinition />
                    <RowDefinition />
                </Grid.RowDefinitions>
                <Label x:Name="lblRegLib" Grid.Row="0" Content="{x:Static resx:resTabBord.lblAchatsBud}"/>
                <Rectangle Grid.Row="1" Fill="{StaticResource scbGrey2}" Margin="-7, 2" Height="1.5" />
                <TextBox x:Name="txtRegLib" Grid.Row="2" Margin="2" Height="24" Visibility="{Binding ElementName=ucTabBord, Path=ModeAff, Converter={StaticResource BoolToVisibility}, ConverterParameter=true}"/>
            </Grid>
            <DataTemplate.Triggers>
              <DataTrigger Binding="{Binding IsActive}" Value="True">
                <Setter TargetName="lblRegLib" Property="Content" Value="Test" />
              </DataTrigger>
            </DataTemplate.Triggers>
        </DataTemplate>
    </DataGridTemplateColumn.HeaderTemplate>

I am just using IsActive as a demonstration that it's possible to trigger changes in the code just by responding to binding changes.

Wpf - find a control in headertemplate and edit it

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