The links below describe how to solve common server-side issues:
The target "X" for the callback could not be found or did not implement ICallbackEventHandler
The controller for ASPxUploadProgressHandlerPage.ashx was not found or does not implement IController
Internal Error. Unable to find the X resource in the Y
Response.Redirect cannot be called in a Page callback
Why you cannot download files on callbacks
A primary key field specified using the KeyFieldName property is not found
The "Key expression is undefined" error occurs when you use LinqServerModeDataSource / EntityServerModeDataSource
Data binding methods such as Eval(), XPath(), and Bind() can only be used for a databound control
Could not find control 'X' in ControlParameter 'Y'
"The X has no access to path Y" or "Access to the path X is denied" (Image and File Controls)
Why redirect to another page or View does not work on AJAX requests
Data binding directly to a store query (DbSet, DbQuery, DbSqlQuery, DbRawSqlQuery) is not supported
An extension with 'X' name is already rendered
'System.Web.WebPages.Html.HtmlHelper' does not contain a definition for 'DevExpress'