Wpf style not fully applied for ContextMenu

Question

I would like to have a context menu in wpf/c# application on mouse left button click. I know this is an unusual behavior but in this very specific situation it is required. This is the xaml-file (reduced to the relevant parts):



    
        #FFAF231E
        #FF9F231E
        #FF8F231E
        #FF601818

        #FFBBBBBB
        #FF737373
        #FF646464
        #FF000000

        #FF8496AA
        #FF414141

Here comes the code (C#):

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace _ContextMenuText
{
/// 
/// Interaction logic for MainWindow.xaml
/// 
public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        ContextMenu cont = new ContextMenu();
        cont.Style = this.FindResource(typeof(ContextMenu)) as Style;
        MenuItem mni = new MenuItem();
        AddStyleToItem(mni);
        mni.Header = "item1";
        cont.Items.Add(mni);

        MenuItem mni1 = new MenuItem();
        AddStyleToItem(mni);
        mni1.Header = "item2";
        mni.Items.Add(mni1);

        MenuItem mni2 = new MenuItem();
        AddStyleToItem(mni);
        mni2.Header = "item22";
        mni.Items.Add(mni2);

        TestLabel.ContextMenu = cont;
    }
    private void AddStyleToItem(MenuItem item)
    {
        item.Style = this.FindResource(typeof(MenuItem)) as Style;
    }
    private void TestLabel_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        TestLabel.ContextMenu.IsOpen = true;
    }
}
}

If I start the program and firstly click on the label with left mouse button, the context menu is not properly styled:

In case of opening the context menu by clicking right mouse button, the context menu is shown correctly:

The point is that after the context menu was opened with right mouse button click, it is also well styled when I open it with left mouse button click. It seems that there is some initialization done when right mouse button is clicked. I was looking for ways to simulate the right mouse button click somehow but that was not successful. In case I raise right mouse button click in code this kind of initialization isn't done. The context menu is shown correctly. I tried to remove the assignment of the style in code:

cont.Style = this.FindResource(typeof(ContextMenu)) as Style;

That leads to almost the same wrong behavior. Only the first design when opening the context menu by right mouse button click firstly is different:

Is there anyone who could help me on that? Many thanks!

Kaspar · Accepted Answer

You need to move content of your ResourceDictionary to App.xaml to Application.Resources - then it will start working and also remove ResourceDictionary in Window Resources. Please let me know if works for you.

Wpf style not fully applied for ContextMenu

Answers (1)

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