Even after so many years of expereince with ADO.Net and SQL, every now and then I run into problems which are very obvious but sometime easy problems become hard to track. I was implementing a data access method and called ExecuteNonQuery method on SqlCommand object and got the above exception thrown. I looked at the code and nothing seemed wrong. Then I started my regular debugging steps and ran Sql profiler. When ExecuteNonQuery method was called, I looked at the trace and I saw something unusual. I was trying to call a stored procedure [dbo].[AddContent]through SqlCommand object. I was expecting to see the sored procedure being called. Instead I saw the following code being executed.

declare @p13 bigint
set @p13=NULL
exec sp_executesql N'[dbo].[AddContent]',N'@AuthorId bigint,@CategoryId bigint...................							
							

Looking at this in profiler gave hint that instead of executing my stored procedure, ADO.Net has tried to execute command text. And then I looked at the implementation thats exactly the problem was. I did not set CommandType property of SqlCommand to CommandType.StoredProcedure. After I set that property the code worked. So if you are specifying a stored procedure as command text, make sure that you have set CommandType property too.