I'm trying to build Ext.Net.MVC project with MVC2 and I'm having an error at line 43 in the AjaxResult class:

'Ext.Net.DirectResponse' does not contain a definition for 'IsUpload' and no extension method 'IsUpload' accepting a first argument of type 'Ext.Net.DirectResponse' could be found (are you missing a using directive or an assembly reference?)
Can I comment this line or am I missing something?