CA1300: Specify MessageBoxOptions


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The latest version of this topic can be found at CA1300: Specify MessageBoxOptions.

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

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
        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()
        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 _
            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

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