> 
> Server Error in '/' Application.
> 
> 
> 'respond' is not a valid script name. The name must end in '.js'.
> 
> 
> Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 
> 
> 
> Exception Details: System.InvalidOperationException: 'respond' is not a valid script name. The name must end in '.js'.
> 
> 
> Source Error: 
> 
> 
> An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
> 
> 
> Stack Trace: 
> 
> 
> [InvalidOperationException: 'respond' is not a valid script name. The name must end in '.js'.]
>  System.Web.UI.ScriptReference.GetDebugName(String releaseName) +140
>  System.Web.UI.ScriptReference.ShouldUseDebugScript(String releaseName, Assembly assembly, Boolean isDebuggingEnabled, Assembly currentAjaxAssembly) +48
>  System.Web.UI.ScriptReference.DetermineResourceNameAndAssembly(ScriptManager scriptManager, Boolean isDebuggingEnabled, String& resourceName, Assembly& assembly) +106
>  System.Web.UI.ScriptReference.GetUrlFromName(ScriptManager scriptManager, IControl scriptManagerControl, Boolean zip, Boolean useCdnPath) +77
>  System.Web.UI.ScriptReference.GetUrlInternal(ScriptManager scriptManager, Boolean zip, Boolean useCdnPath) +370
>  System.Web.UI.ScriptReference.GetUrlInternal(ScriptManager scriptManager, Boolean zip) +61
>  System.Web.UI.ScriptReference.GetUrl(ScriptManager scriptManager, Boolean zip) +123
>  System.Web.UI.ScriptManager.RegisterUniqueScripts(List`1 uniqueScripts) +167
>  System.Web.UI.ScriptManager.RegisterScripts() +405
>  System.Web.UI.ScriptManager.OnPagePreRenderComplete(Object sender, EventArgs e) +145
>  System.Web.UI.Page.OnPreRenderComplete(EventArgs e) +9753946
>  System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5054
> 
> 
> 

I don't know where to even begin looking for the cause of this error
Happens when i debug my ASP.NET web app in VS2015.

It seems to have happened if I deleted `Global.asax` class because before that it would work locally but not when deployed to web when it threw type ambiguous errors.
I have now since re-added the `Global.asax` class, but to no avail.