Determine Whether Program is the Active Window in .NET

Question

I have a C#/.NET app and I want to implement the following behavior:

I have a popup menu. Whenever the user clicks on anything within the application that

Answer 1

I stumbled upon your question while working on a project and based on Reed Copsey's answer, I wrote this quick code which seems to do the job well.

Here's the code:

Public Class Form1
    '''

    '''Returns a handle to the foreground window.
    '''
     _
    Private Shared Function GetForegroundWindow() As IntPtr
    End Function

    '''

    '''Gets a value indicating whether this instance is foreground window.
    '''
    '''
    '''true if this is the foreground window; otherwise, false.
    '''
    Private ReadOnly Property IsForegroundWindow As Boolean
        Get
            Dim foreWnd = GetForegroundWindow()
            Return ((From f In Me.MdiChildren Select f.Handle).Union(
                    From f In Me.OwnedForms Select f.Handle).Union(
                    {Me.Handle})).Contains(foreWnd)
        End Get
    End Property
End Class

I didn't have too much time to convert it to C# as I'm working on a project with a deadline in 2 days but I believe you can quickly do the conversion.

Here is the C# version of the VB.NET code:

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    [System.Runtime.InteropServices.DllImport("user32.dll")]
    private static extern IntPtr GetForegroundWindow();

    ///
Gets a value indicating whether this instance is foreground window.
    ///true if this is the foreground window; otherwise, false.
    private bool IsForegroundWindow
    {
        get
        {
            var foreWnd = GetForegroundWindow();
            return ((from f in this.MdiChildren select f.Handle)
                .Union(from f in this.OwnedForms select f.Handle)
                .Union(new IntPtr[] { this.Handle })).Contains(foreWnd);
        }
    }
}