SPUtility.IsDesignTimeRender method
SharePoint 2013
Indicates whether the current request is run in a design-time context. Usually this is because a Web service call is made by a Microsoft SharePoint Foundation-compatible editor, for example Microsoft SharePoint Designer 2010.
Assembly: Microsoft.SharePoint (in Microsoft.SharePoint.dll)
[SubsetCallableExcludeMemberAttribute(SubsetCallableExcludeMemberType.PerSpec)] public static bool IsDesignTimeRender()
Return value
Type: System.Booleantrue if the request is run in a design-time context; otherwise, false.