CA1300: Specify MessageBoxOptions

Cause

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

Rule Description

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

How to Fix Violations

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

When to Suppress Warnings

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.

Example

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
    {
        [STAThread]
        static void Main()
        {
            SomeForm myForm = new SomeForm();
            // Uncomment the following line to test the right-to-left feature.
            //myForm.RightToLeft = RightToLeft.Yes;
            Application.Run(myForm);
        }
    }

    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);
            Controls.Add(_Button);
        }

        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 |
                MessageBoxOptions.RightAlign;
            }

            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;
        }
    }
}

Imports System
Imports System.Globalization
Imports System.Resources
Imports System.Windows.Forms

Namespace GlobalizationLibrary
    Class Program
    
        <STAThread()> _
        Shared Sub Main()
            Dim myForm As New SomeForm()
            
            ' Uncomment the following line to test the right to left feature.
            ' myForm.RightToLeft = RightToLeft.Yes
            Application.Run(myForm)
        End Sub
    End Class

    Public Class SomeForm : Inherits Form
        Private _Resources As ResourceManager
        Private WithEvents _Button As Button

        Public Sub New()
            _Resources = New ResourceManager(GetType(SomeForm))
            _Button = New Button()
            Controls.Add(_Button)
        End Sub

        Private Sub Button_Click(ByVal sender As Object, ByVal e As EventArgs) Handles _Button.Click
            ' Switch the commenting on the following 4 lines to test the form.
            'Dim text As String = "Text"
            'Dim caption As String = "Caption"
            Dim text As String = _Resources.GetString("messageBox.Text")
            Dim caption As String = _Resources.GetString("messageBox.Caption")
            
            RtlAwareMessageBox.Show(CType(sender, Control), text, caption, _
            MessageBoxButtons.OK, MessageBoxIcon.Information, _
            MessageBoxDefaultButton.Button1, CType(0, MessageBoxOptions))
        End Sub
    End Class

    Public Module RtlAwareMessageBox

        Public Function Show(ByVal owner As IWin32Window, ByVal text As String, ByVal caption As String, ByVal buttons As MessageBoxButtons, ByVal icon As MessageBoxIcon, ByVal defaultButton As MessageBoxDefaultButton, ByVal options As MessageBoxOptions) As DialogResult
            If (IsRightToLeft(owner)) Then
                options = options Or MessageBoxOptions.RtlReading Or _
                MessageBoxOptions.RightAlign
            End If

            Return MessageBox.Show(owner, text, caption, _
            buttons, icon, defaultButton, options)
        End Function

        Private Function IsRightToLeft(ByVal owner As IWin32Window) As Boolean
            Dim control As Control = TryCast(owner, Control)

            If (control IsNot Nothing) Then
                Return control.RightToLeft = RightToLeft.Yes
            End If

            ' If no parent control is available, ask the CurrentUICulture
            ' if we are running under right-to-left.
            Return CultureInfo.CurrentUICulture.TextInfo.IsRightToLeft
        End Function
    End Module
End Namespace

See Also

System.Resources.ResourceManager Resources in Desktop Apps