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Control.ControlAccessibleObject Constructor

Initializes a new instance of the Control.ControlAccessibleObject class.

[Visual Basic]
Public Sub New( _
   ByVal ownerControl As Control _
)
[C#]
public Control.ControlAccessibleObject(
   Control ownerControl
);
[C++]
public: ControlAccessibleObject(
   Control* ownerControl
);
[JScript]
public function Control.ControlAccessibleObject(
   ownerControl : Control
);

Parameters

ownerControl
The Control that owns the Control.ControlAccessibleObject.

Exceptions

Exception Type Condition
ArgumentNullException The ownerControl parameter value is a null reference (Nothing in Visual Basic).

Example

[Visual Basic, C#, C++] The following example creates a check box control that derives from the CheckBox class and creates a custom Control.ControlAccessibleObject for the derived class to use. The derived class, MyCheckBox, has an Appearance of Button by default so it appears as a toggle button. The derived Control.ControlAccessibleObject class, MyCheckBoxControlAccessibleObject, overrides three properties to account for the difference in appearance.

[Visual Basic] 
Imports System
Imports System.Windows.Forms
Imports Accessibility
Imports System.Drawing

Namespace MyCustomControls
   Public Class MyCheckBox
      Inherits CheckBox
      
      Public Sub New()
         ' Make the check box appear like a toggle button.
         Me.Appearance = Appearance.Button
         ' Center the text on the button.
         Me.TextAlign = ContentAlignment.MiddleCenter
      End Sub
      
      ' Create an instance of the AccessibleObject 
      ' defined for the 'MyCheckBox' control 
      Protected Overrides Function CreateAccessibilityInstance() _
        As AccessibleObject
         Return New MyCheckBoxAccessibleObject(Me)
      End Function
   End Class
    
   ' Accessible object for use with the 'MyCheckBox' control.
   Friend Class MyCheckBoxAccessibleObject
      Inherits Control.ControlAccessibleObject
      
      Public Sub New(owner As MyCheckBox)
         MyBase.New(owner)
      End Sub
      
      Public Overrides ReadOnly Property DefaultAction() As String
         Get
            ' Return the DefaultAction based upon 
            ' the state of the control. 
            If CType(Owner, MyCheckBox).Checked Then
               Return "Toggle button up"
            Else
               Return "Toggle button down"
            End If
         End Get
      End Property
      
      Public Overrides Property Name() As String
         Get
            ' Return the Text property of the control 
            ' if the AccessibleName is null. 
            Dim accessibleName As String = Owner.AccessibleName
            If Not (accessibleName Is Nothing) Then
               Return accessibleName
            End If
            Return CType(Owner, MyCheckBox).Text
         End Get

         Set
            MyBase.Name = value
         End Set
      End Property
      
      Public Overrides ReadOnly Property Role() As AccessibleRole
         Get
            ' Since the check box appears like a button,
            ' make the Role the same as a button. 
            Return AccessibleRole.PushButton
         End Get
      End Property
   End Class
End Namespace

[C#] 
using System;
using System.Windows.Forms;
using Accessibility;
using System.Drawing;

namespace MyCustomControls
{
   public class MyCheckBox : CheckBox
   {
      public MyCheckBox()
      {
         // Make the check box appear like a toggle button.
         this.Appearance = Appearance.Button;
         // Center the text on the button.
         this.TextAlign = ContentAlignment.MiddleCenter;
     // Set the AccessibleDescription text.
         this.AccessibleDescription = "A toggle style button.";
      }
      
      // Create an instance of the AccessibleObject 
      // defined for the 'MyCheckBox' control
      protected override AccessibleObject CreateAccessibilityInstance() 
      {
         return new MyCheckBoxAccessibleObject(this);
      }
   }

   // Accessible object for use with the 'MyCheckBox' control.
   internal class MyCheckBoxAccessibleObject : Control.ControlAccessibleObject 
   {
      public MyCheckBoxAccessibleObject(MyCheckBox owner) : base(owner) 
      {
        
      }
               
      public override string DefaultAction 
      {
         get
         {
            // Return the DefaultAction based upon 
            // the state of the control.
            if( ((MyCheckBox)Owner).Checked )
            {
               return "Toggle button up";
            }
            else
            {
               return "Toggle button down";
            }
         }
      }

      public override string Name 
      {
         get 
         {
            // Return the Text property of the control 
            // if the AccessibleName is null.
            string name = Owner.AccessibleName;
            if (name != null) 
            {
               return name;
            }
            return ((MyCheckBox)Owner).Text;
         }
         
         set
         {
            base.Name = value;
         }
      }            
               
      public override AccessibleRole Role 
      {
         get 
         {
            // Since the check box appears like a button,
            // make the Role the same as a button.
            return AccessibleRole.PushButton;
         }
      }
   }
}

[C++] 
#using <mscorlib.dll>
#using <Accessibility.dll>
#using <System.Drawing.dll>
#using <System.dll>
#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::Windows::Forms;
using namespace System::Drawing;

namespace MyCustomControls {
public __gc class MyCheckBox : public CheckBox {
public:
   MyCheckBox() {
      // Make the check box appear like a toggle button.
      this->Appearance = Appearance::Button;
      // Center the text on the button.
      this->TextAlign = ContentAlignment::MiddleCenter;
      // Set the AccessibleDescription text.
      this->AccessibleDescription = S"A toggle style button.";
   }

   // Create an instance of the AccessibleObject
   // defined for the 'MyCheckBox' control
protected:
   AccessibleObject* CreateAccessibilityInstance();
};

// Accessible Object* for use with the 'MyCheckBox' control.
private __gc class MyCheckBoxAccessibleObject : public Control::ControlAccessibleObject {
public:
   MyCheckBoxAccessibleObject(MyCheckBox* owner) : ControlAccessibleObject(owner) {
   }

   __property String* get_DefaultAction() {
      // Return the DefaultAction based upon
      // the state of the control.
      if ((dynamic_cast<MyCheckBox*>(Owner))->Checked) {
         return S"Toggle button up";
      } else {
         return S"Toggle button down";
      }
   }

   __property String* get_Name() {
      // Return the Text property of the control
      // if the AccessibleName is 0.
      String* name = Owner->AccessibleName;
      if (name != 0) {
         return name;
      }
      return (dynamic_cast<MyCheckBox*>(Owner))->Text;
   }
   __property void set_Name(String* value) {
      ControlAccessibleObject::set_Name(value);
   }

   __property AccessibleRole get_Role() {
      // Since the check box appears like a button,
      // make the Role the same as a button.
      return AccessibleRole::PushButton;
   }
};

AccessibleObject* MyCheckBox::CreateAccessibilityInstance() {
   return new MyCheckBoxAccessibleObject(this);
}
}

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

See Also

Control.ControlAccessibleObject Class | Control.ControlAccessibleObject Members | System.Windows.Forms Namespace | Control.ControlAccessibleObject | Owner

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