What is wrong with this simple update query?

Programmer Question

I get no error message, but the row is not updated. The rows integer is set 1 following the query, indicating that 1 row was affected.

String query = "UPDATE contacts SET contact_name = '" + ContactName.Text.Trim() + "', " +
            "contact_phone = '" + Phone.Text.Trim() + "', " +
            "contact_fax = '" + Fax.Text.Trim() + "', " +
            "contact_direct = '" + Direct.Text.Trim() + "', " +
            "company_id = '" + Company.SelectedValue + "', " +
            "contact_address1 = '" + Address1.Text.Trim() + "', " +
            "contact_address2 = '" + Address2.Text.Trim() + "', " +
            "contact_city = '" + City.Text.Trim() + "', " +
            "contact_state = '" + State.SelectedValue + "', " +
            "contact_zip = '" + Zip.Text.Trim() + "' " + 
            "WHERE contact_id = '" + contact_id + "'";



        String cs = Lib.GetConnectionString(null);
        SqlConnection conn = new SqlConnection(cs);
        SqlCommand cmd = conn.CreateCommand();
        cmd.CommandText = query;
        cmd.Connection.Open();
        int rows = cmd.ExecuteNonQuery();

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