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Form.ActiveForm Property

Gets the currently active form for this application.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

public static Form ActiveForm { get; }

Property Value

Type: System.Windows.Forms.Form
A Form that represents the currently active form, or null if there is no active form.

You can use this method to obtain a reference to the currently active form to perform actions on the form or its controls.

If your application is a multiple-document interface (MDI) application, use the ActiveMdiChild property to obtain the currently active MDI child form.

The following code example gets the active form and disables all the controls on the form. The example uses the Controls collection of the form to iterate through each control on the form and disable the controls.

public void DisableActiveFormControls()
    // Create an instance of a form and assign it the currently active form.
    Form currentForm = Form.ActiveForm;

    // Loop through all the controls on the active form. 
    for (int i = 0; i < currentForm.Controls.Count; i++)
       // Disable each control in the active form's control collection.
       currentForm.Controls[i].Enabled = false;

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0