AjaxControlToolkit没有通过WebResource.axd加载css导致ajaxToolkit:TabPanel无法显示正确的样式

what-is-webresource-axd

WebResource.axd provides access to embedded resources within a project. It's a handler that enables control and page developers to download resources that are embedded in an assembly to the end user.

You include WebResources in your AssemblyInfo:

[assembly: System.Web.UI.WebResource("Project.Styles.Main.css", "text/css")]

Then you can get an include path for your Page using the following code:

string includeLocation = Page.ClientScript.GetWebResourceUrl(this.GetType(),    
    "Project.Styles.Main.css");

Then to add the above file (which is a CSS file in this case):

LiteralControl include = new LiteralControl(
    String.Format(includeTemplate, includeLocation));

((System.Web.UI.HtmlControls.HtmlHead)Page.Header).Controls.Add(include);

Then you'll end up seeing references within your page source such as the following:

/WebResource.axd?d=PhPk80h_UWEcbheb-NHNP5WshV_47UOpWqAOl1_li
    UFfN4cNofL74cFlQ1fvpFSf0&t=632573240669964903

https://github.com/DevExpress/AjaxControlToolkit/wiki/How-to-use-bundling-and-CDN

To disable bundling:

remove ScriptReference from ScriptManager
remove the Style.Render expression from the element
in the “ajaxControlToolkit” config section (Web.config), set the “renderStyleLinks” attribute to “true”, and the “useStaticResources” attribute to “false”

只需要将renderStyleLinks设置为true就可以，另外一个attribute默认就是false