Cannot insert the value NULL into column 'Doc_ID', table 'C:\INETPUB\WWWROOT\WEB\APP_DATA\DATABASE.MDF.dbo.upload'; column does not allow nulls. INSERT fails.
The statement has been terminated. 
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.Data.SqlClient.SqlException: Cannot insert the value NULL into column 'Doc_ID', table 'C:\INETPUB\WWWROOT\WEB\APP_DATA\DATABASE.MDF.dbo.upload'; column does not allow nulls. INSERT fails.
The statement has been terminated.

Source Error: 


Line 38:     mycommand.Parameters.Add("@contenttype", SqlDbType.VarChar).Value = inputFile.PostedFile.ContentType;
Line 39:     myconnection.Open();
Line 40:     mycommand.ExecuteNonQuery();
Line 41:     myconnection.Close();
Line 42:     Response.Redirect("success.html") ;
 

 mycommand.Parameters.Add("@Doc_ID", SqlDbType.Int).????