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Custom skins not applied or overridden by base Telerik stylesheets


Render Mode Lightweight


The Skins generated from the Telerik ThemeBuilder are generated with the same selectors's specificity as the built-in base styles. Sometimes, depending on the skin and scenario, the base Telerik styles are overriding styles from the custom skins. This is considered an issue with the skins themselves and will be fixed in upcoming versions of the controls. In the meantime the solution below can be used.


The Telerik ThemeBuilder allows customizing skins for the Lightweight render mode of the Telerik UI for ASP.NET AJAX controls. Increasing the Selectors' specificity would prevent any base stylesheets from overriding it.

Example: .RadAutoCompleteBox_CustomSkin selector to become .RadAutoCompleteBox.RadAutoCompleteBox_CustomSkin.

Here is a code snippet of the application that programmatically increases the selector's specificity. The fully runnable WebForms WebSite can be downloaded from here.

<asp:ScriptManager runat="server" />
<asp:Button runat="server" ID="Button1" Text="Increase selectors" OnClick="Button1_Click" AutoPostBack="true" />
<asp:TextBox ID="tbSkinName" runat="server"  placeholder="Enter SkinName here..."></asp:TextBox>
<asp:RequiredFieldValidator ForeColor="DarkRed" ErrorMessage="*Please enter skin name" ControlToValidate="tbSkinName" runat="server" />
<asp:Label runat="server" ID="Label1"></asp:Label>
public static string SkinName = "";

public static string SelectorStrenghEnhancer(Match match)
    var matchString = match.Value;
    var control = matchString.Substring(0, matchString.Length - ("_" + SkinName).Length);
    var finalString = control + matchString;

    return finalString;

protected void Button1_Click(object sender, EventArgs e)
    SkinName = tbSkinName.Text;

    var inputPath = Server.MapPath("~/Input");
    var outputPath = Server.MapPath("~/Output");

    var files = Directory.GetFiles(inputPath, "*.css");
    MatchEvaluator evaluator = new MatchEvaluator(SelectorStrenghEnhancer);

    foreach (var filePath in files)
        string text = File.ReadAllText(filePath);
        var filename = Path.GetFileName(filePath);
        text = Regex.Replace(text, @"\.Rad.*?_"+ SkinName, evaluator, RegexOptions.IgnorePatternWhitespace);
        File.WriteAllText(Path.Combine(outputPath,filename), text);

    Label1.Text = "Styles selectors increased successfully";

Instructions to use the project

  • Place the custom skin .css files in ~/Input folder of the project
  • Open the project with Visual Studio and run it
  • Set the name of the custom skin in the TextBox
  • Press the button
  • Get the new .css files from the ~/Output folder and apply them in your
  • Apply the custom theme in your project

See Also

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