Passing NULL values to SqlCommand.Parameters.AddWithValue

this code might help

       
SqlCommand sqlCmd = new SqlCommand(sqlStatment, dbConn);
sqlCmd.Parameters.AddWithValue("@Name", name);
sqlCmd.Parameters.AddWithValue("@Surname", surname);
foreach (SqlParameter Parameter in sqlCmd.Parameters)
{
        if (Parameter.Value == null)
        {
                Parameter.Value = DBNull.Value;
        }
}

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