I'm having a problem when dynamically adding a DataTrigger to an existing element.

在向現有元素動態添加DataTrigger時遇到問題。

If I hard-code it in MainWindow.XAML like this it works fine:

如果我在MainWindow.XAML中對它進行硬編碼，那么它可以正常工作：

In App.Xaml:

在App.Xaml中：

...
<Application.Resources>
    <ControlTemplate x:Key="MyTemplate">
        <TextBox AcceptsReturn="True" AcceptsTab="True" AllowDrop="True" Text="{Binding Content}"/>
    </ControlTemplate>
</Application.Resources>
...

In MainWindow.XAML:

在MainWindow.XAML中：

...
<DataTemplate>
    <Control x:Name="ViewPlaceHolder" Template="{StaticResource ViewPlaceHolderTemplate}" />
    <DataTemplate.Triggers>
        <DataTrigger Binding="{Binding TypeName}" Value="MyViewModelName">
            <Setter TargetName="ViewPlaceHolder" Property="Template" Value="{StaticResource MyTemplate}" />
        </DataTrigger>
    </DataTemplate.Triggers>
</DataTemplate>
...

But if I create the DataTrigger in code behind as follows:

但是如果我在后面的代碼中創建DataTrigger如下：

...
    DataTrigger tr = new DataTrigger();
    Binding b = new Binding();
    b.Path = new PropertyPath("TypeName");
    tr.Value = triggerValue;
    tr.Binding = b;
    Setter st = new Setter(Control.TemplateProperty, "{StaticResource MyTemplate}");
    st.TargetName = "ViewPlaceHolder";
    tr.Setters.Add(st);
    myDataTemplate.Triggers.Add(tr);
...

I get the following error during binding (there is no error when I add the trigger to the template and using XamlWriter.Write(myDataTemplate) shows its been added to the DataTemplate properly):

我在綁定期間遇到以下錯誤（當我將觸發器添加到模板並使用XamlWriter.Write（myDataTemplate）顯示它已正確添加到DataTemplate時沒有錯誤）：

'StaticResource MyTemplate' is not a valid value for the 'System.Windows.Controls.Control.Template' property on a Setter.

'StaticResource MyTemplate'不是Setter上'System.Windows.Controls.Control.Template'屬性的有效值。

I have to load the Trigger at runtime because it (triggerValue) comes from an dynamically loaded plugin. If I add the ControlTemplate directly to the Setter instead of referencing it as a StaticResource it also works fine but I don't like the idea of having to load the same ControlTemplate on every page/window where I might need it.

我必須在運行時加載Trigger，因為它（triggerValue）來自動態加載的插件。如果我將ControlTemplate直接添加到Setter而不是將其作為StaticResource引用它也可以正常工作，但我不喜歡必須在我可能需要它的每個頁面/窗口上加載相同的ControlTemplate。

Any idea of how I can get the Setter in the DataTrigger to reference the resource if I add it from Code behind?

如果我從Code后面添加它，我怎么能在DataTrigger中獲取Setter來引用資源？

1 个解决方案

var myTemplate = Application.Current.TryFindResource("MyTemplate") as ControlTemplate;
// Do something appropriate if myTemplate is null
Setter st = new Setter(Control.TemplateProperty, myTemplate);