Index and length must refer to a location within the string?!

 
 MySqlCommand command4 = Form2.connection.CreateCommand();
            command4.CommandText = "update products_to_categories set products_name='" + textBox1.Text + "', products_description='" + textBox8.Text.Replace("\r\n", "
") + "' WHERE products_id=" + id + " AND language_id=4";
            command4.ExecuteNonQuery();