getting exception error -SPFieldType.File -“Operation is not valid due to the current state of the object.”

Question

creating a Field of type File and Attachments in document library and getting exception error as mentioned above.Please help me out thanks in advance..

Guid listid1 = web.Lists.Add("TESTLIBRARY", "THIS LIST IS FOR TESTING", 
                             SPListTemplateType.DocumentLibrary);

SPList documentlibrary = web.Lists["TESTLIBRARY"];
documentlibrary.ContentTypesEnabled = true;

documentlibrary.Fields.Add("Employee Attachments", SPFieldType.File, false);
                    documentlibrary.Update(); 

Answer 1

Having attachments on document libraries and surveys is not supported.

In addition, you don't add an attachments column to a list in general. The way to enable attachments is to set the EnableAttachments property on a list to true.

SPList list = web.Lists["LISTNAME"]; 
list.EnableAttachments = true;
list.Update();

The code above will throw an exception if the list is a document library or survey