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WindowsFormsApplicationBase.OpenForms Property

  • Reference

Definition

Namespace:
Microsoft.VisualBasic.ApplicationServices
Assembly:
Microsoft.VisualBasic.dll
Assembly:
Microsoft.VisualBasic.Forms.dll
Source:
WindowsFormsApplicationBase.vb
Source:
WindowsFormsApplicationBase.vb
Source:
WindowsFormsApplicationBase.vb

Gets a collection of all the application's open forms.

public:
 property System::Windows::Forms::FormCollection ^ OpenForms { System::Windows::Forms::FormCollection ^ get(); };
public System.Windows.Forms.FormCollection OpenForms { get; }
member this.OpenForms : System.Windows.Forms.FormCollection
Public ReadOnly Property OpenForms As FormCollection

Property Value

FormCollection

A collection that contains all of the application's open forms.

Examples

This example loops over the application's open forms, selects the ones directly accessible by the current thread, and displays their titles in a ListBox control. This example requires that your Windows Forms application have a form named Form1 that contains a list box named ListBox1.

Private Sub GetOpenFormTitles()
    Dim formTitles As New Collection

    Try
        For Each f As Form In My.Application.OpenForms
            If Not f.InvokeRequired Then
                ' Can access the form directly.
                formTitles.Add(f.Text)
            End If
        Next
    Catch ex As Exception
        formTitles.Add("Error: " & ex.Message)
    End Try

    Form1.ListBox1.DataSource = formTitles
End Sub

This example loops over the application's open forms and displays their titles in a ListBox control.

Private Sub GetOpenFormTitles()
    Dim formTitles As New Collection

    Try
        For Each f As Form In My.Application.OpenForms
            ' Use a thread-safe method to get all form titles.
            formTitles.Add(GetFormTitle(f))
        Next
    Catch ex As Exception
        formTitles.Add("Error: " & ex.Message)
    End Try

    Form1.ListBox1.DataSource = formTitles
End Sub

Private Delegate Function GetFormTitleDelegate(f As Form) As String
Private Function GetFormTitle(f As Form) As String
    ' Check if the form can be accessed from the current thread.
    If Not f.InvokeRequired Then
        ' Access the form directly.
        Return f.Text
    Else
        ' Marshal to the thread that owns the form. 
        Dim del As GetFormTitleDelegate = AddressOf GetFormTitle
        Dim param As Object() = {f}
        Dim result As System.IAsyncResult = f.BeginInvoke(del, param)
        ' Give the form's thread a chance process function.
        System.Threading.Thread.Sleep(10)
        ' Check the result.
        If result.IsCompleted Then
            ' Get the function's return value.
            Return "Different thread: " & f.EndInvoke(result).ToString
        Else
            Return "Unresponsive thread"
        End If
    End If
End Function

Remarks

The My.Application.OpenForms property gets a collection of all the application's open forms. The behavior is identical to the Application.OpenForms property.

Note

The My.Application.OpenForms property returns all open forms, regardless of which thread opened them. You should check the InvokeRequired property of each form before accessing it; otherwise, it might throw an InvalidOperationException exception.

Availability by Project Type

Project type Available
Windows Forms Application Yes
Class Library No
Console Application No
Windows Forms Control Library No
Web Control Library No
Windows Service No
Web Site No

Applies to

See also