I'm not sure what could be the problem here. I have tested locally in our Demo application. The steps in my test scenario are:
1. Drag and drop a new instance of RadButton
2. Subscribe to button click event.
3. Create a new RadToolStrip and add RadToolStripElement and RadToolStripItem to it, then modify its theme and change it to "Desert".
private void radButton2_Click(object sender, EventArgs e)
RadToolStrip toolStrip = new RadToolStrip();
toolStrip.Size = new Size(150, 30);
RadToolStripElement toolStripElement = new RadToolStripElement();
RadToolStripItem toolStripItem = new RadToolStripItem();
toolStrip.ThemeName = "Desert";
The following code worked for me. Please make sure that the Theme component is added to the component tray when you change the theme. In my case I had to drag and drop the Desert Theme component.
Please write me back if the information here has helped you. If not I will greatly appreciate if you send me a sample project demonstrating the issue and I will do my best to fix it.
the Telerik team