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CA1300: Specify MessageBoxOptions







Breaking Change


A method calls an overload of the MessageBox.Show method that does not take a MessageBoxOptions argument.

To display a message box correctly for cultures that use a right-to-left reading order, the RightAlign and RtlReading members of the MessageBoxOptions enumeration must be passed to the Show method. Examine the Control.RightToLeft property of the containing control to determine whether to use a right-to-left reading order.

To fix a violation of this rule, call an overload of the Show method that takes a MessageBoxOptions argument.

It is safe to suppress a warning from this rule when the code library will not be localized for a culture that uses a right-to-left reading order.

The following example shows a method that displays a message box that has options that are appropriate for the reading order of the culture. A resource file, which is not shown, is required to build the example. Follow the comments in the example to build the example without a resource file and to test the right-to-left feature.

using System;
using System.Globalization;
using System.Resources;
using System.Windows.Forms;

namespace GlobalizationLibrary
    class Program
        static void Main()
            SomeForm myForm = new SomeForm();
            // Uncomment the following line to test the right-to-left feature. 
            //myForm.RightToLeft = RightToLeft.Yes;

    public class SomeForm : Form
        private ResourceManager _Resources;
        private Button _Button;
        public SomeForm()
            _Resources = new ResourceManager(typeof(SomeForm));
            _Button = new Button();
            _Button.Click += new EventHandler(Button_Click);

        private void Button_Click(object sender, EventArgs e)
            // Switch the commenting on the following 4 lines to test the form. 
            // string text = "Text";
            // string caption = "Caption";
            string text = _Resources.GetString("messageBox.Text");
            string caption = _Resources.GetString("messageBox.Caption");
            RtlAwareMessageBox.Show((Control)sender, text, caption,
            MessageBoxButtons.OK, MessageBoxIcon.Information,
            MessageBoxDefaultButton.Button1, (MessageBoxOptions)0);

    public static class RtlAwareMessageBox
        public static DialogResult Show(IWin32Window owner, string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon, MessageBoxDefaultButton defaultButton, MessageBoxOptions options)
            if (IsRightToLeft(owner))
                options |= MessageBoxOptions.RtlReading |

            return MessageBox.Show(owner, text, caption,
            buttons, icon, defaultButton, options);

        private static bool IsRightToLeft(IWin32Window owner)
            Control control = owner as Control;

            if (control != null)
                return control.RightToLeft == RightToLeft.Yes;

            // If no parent control is available, ask the CurrentUICulture 
            // if we are running under right-to-left. 
            return CultureInfo.CurrentUICulture.TextInfo.IsRightToLeft;