C# ASP.Net Parameters.AddWithValue rejecting null value for parameter

Question

I am populating tables using a stored procedure. The table allows a 'null' for the middle initial of the name, but I'm getting the following error message:

Procedure or function 'uspInsertPersonalAccountApplication' expects parameter '@MiddleInitial', which was not supplied.

Thanks in advance!

   public void ProcessForm(string[] InputData)
    {
        string ConnString = System.Configuration.ConfigurationManager.ConnectionStrings["AssociatedBankConnectionString"].ToString();

        SqlConnection conn = new SqlConnection(ConnString);
        SqlCommand cmd = new SqlCommand("uspInsertPersonalAccountApplication", conn);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.AddWithValue("@AccountType", "Savings");
        cmd.Parameters.AddWithValue("@AccountSubType", "Savings");
        cmd.Parameters.AddWithValue("@ExistingCustomer","No");
        conn.Open();
        cmd.ExecuteNonQuery();

        conn.Close();
    }

Answer 1

You can add to project and use following extension method:

public static SqlParameter AddWithValueSafe(this SqlParameterCollection parameters, string parameterName, object value)
{
    return parameters.AddWithValue(parameterName, value ?? DBNull.Value);
}

Answer 2

There are two options here:

Modify you stored procedure and make @MiddleInitial param optional (which is currently not optional that's why error is thrown)

@MiddleInitial nvarchar(10) = NULL

Or add following line to your code:

cmd.Parameters.AddWithValue("@MiddleInitial", null);