Following code is how to pass NULL to SQL using parameter

myCmd.Parameters.Add("@Phone", SqlDbType.Decimal).Value = string.IsNullOrEmpty(txtPhone.Text) ? DBNull.Value : (object)Decimal.Parse(txtPhone.Text);

Any idea how to do this in LINQ to SQL

Phone = string.IsNullOrEmpty(txtPhone.Text) ? null : Convert.ToDecimal(txtPhone.Text),

This way its give error since the field Phone in SQL is numeric..