Question

I had ddl which determine gender and user can donot choose any value from ddl so i tried to check if user didnot select any value from ddl inser null value or any value in database i made that but error apear(Procedure or Function ‘InsertRegisteration’ expects parameter ‘@Gender_Id’, which was not supplied).any one help me

(My Code)

 if (DDLGender.SelectedItem.Value[0]!= null )
  {
    command.Parameters.Add("@Gender_Id",SqlDbType.Int).Value=null;
  }
  else
  {
    command.Parameters.Add(Parameter.NewInt("@Gender_Id", DDLGender.SelectedValue));
  }

Answer 1

Try this:

if (DDLGender.SelectedItem.Value[0]!= null ) 
{ 
   command.Parameters.Add("@Gender_Id",SqlDbType.Int).Value= DBNull.Value; 
} 
else 
{    
   command.Parameters.Add(Parameter.NewInt("@Gender_Id", DDLGender.SelectedValue)); 
}

Added : Difference between null and System.DbNull.Value

Well, null is not an instance of any type. Rather, it is an invalid reference.

However, System.DbNull.Value, is a valid reference to an instance of System.DbNull (System.DbNull is a singleton and System.DbNull.Value gives you a reference to the single instance of that class) that represents nonexistent^* values in the database.

^{*We would normally say null, but I don’t want to confound the issue.}

So, there’s a big conceptual difference between the two. The keyword null represents an invalid reference. The class System.DbNull represents a nonexistent value in a database field. In general, we should try avoid using the same thing (in this case null) to represent two very different concepts (in this case an invalid reference versus a nonexistent value in a database field).

Keep in mind, this is why a lot of people advocate using the null object pattern in general, which is exactly what System.DbNull is an example of.