OnApplyTemplate not called in Custom Control

Question

I have a Custom Control which uses some PART controls:

 [TemplatePart(Name = "PART_TitleTextBox", Type = typeof(TextBox))]
    [TemplatePart(Name = "PART_TitleIndexText", Type = typeof(Label))]
    [TemplatePart(Name = "PART_TimeCodeInText", Type = typeof(TextBlock))]
    [TemplatePart(Name = "PART_TimeCodeOutText", Type = typeof(TextBlock))]
    [TemplatePart(Name = "PART_ApprovedImage", Type = typeof(Image))]
    [TemplatePart(Name = "PART_CommentsImage", Type = typeof(Image))]
    [TemplatePart(Name = "PART_BookmarkedImage", Type = typeof(Image))]
    public class TitleBoxNew : Control
    {
        static TitleBoxNew()
        { 
            DefaultStyleKeyProperty.OverrideMetadata(
                typeof(TitleBoxNew),
                new FrameworkPropertyMetadata(typeof(TitleBoxNew)));
        } 

        public TitleBoxNew() { }

        // ... rest of class
    }

This control is overriding OnApplyTemplate:

public override void OnApplyTemplate()
{
      base.OnApplyTemplate();

      InitializeEvents();
}

Which works well, most of the time. I have added the control inside a custom tab control in a window and somehow OnApplyTemplate is never called for that control! Why doesn't this work as I expect?

Answer 1

For anyone else who might stumble upon this post, I was having the same issue and I managed to solve it by adding the following into the AssemblyInfo.cs of the project containing my custom control:

[assembly: ThemeInfo(
    ResourceDictionaryLocation.None, //where theme specific resource dictionaries are located
    //(used if a resource is not found in the page, 
    // or application resource dictionaries)
    ResourceDictionaryLocation.SourceAssembly //where the generic resource dictionary is located
    //(used if a resource is not found in the page, 
    // app, or any theme specific resource dictionaries)
)]

My control's template is located in the file Theme/Generic.xaml in the same project as the control.

Answer 2

The other two answers are correct...but not complete. According to this post (and my experience of just resolving this issue) there are 4 things you need to check: (for some reason the code blocks in this post wouldn't stay formatted if I used numbers or dashes...so letters it is)

A. The controls template and styles should be located in the Generic.xaml file a folder called Themes of the root of your project.

B. Make sure your namespaces are correct in the Generic.xaml

C. Set the style key in the constructor of your control. It is also widely recommended you put the following in a static constructor.

 static YourControl()
 {
      DefaultStyleKeyProperty.OverrideMetadata(typeof(YourControl), new FrameworkPropertyMetadata(typeof(YourControl)));
 }

D. Ensure the following is in your assemblyinfo.cs

 [assembly: ThemeInfo(ResourceDictionaryLocation.None, 
 //where theme specific resource dictionaries are located
 //(used if a resource is not found in the     
 // or application resource dictionaries)
 ResourceDictionaryLocation.SourceAssembly 
 //where the generic resource dictionary is located
 //(used if a resource is not found in the page,
 // app, or any theme specific resource dictionaries)
 )]