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.net – VSTO: Application Focus

Posted by: admin March 9, 2020 Leave a comment


Anyone know of a way to see if the Excel window of a VSTO project is active/in focus?

I’m looking for an equivalent of System.Windows.Window.IsActive.

How to&Answers:

I’ve been frustrated with this as well. Are you using a dialog in the VSTO app? If so, what I have done is add an event to the closing of a Windows Form/Dialog to activate the Office application as follows (example is with Word, so there may be differences in Excel):

//... VSTO Startup Event
WindowsForm form = new WindowsForm();
form.FormClosed += new FormClosedEventHandler(form_FormClosed);

void form_FormClosed(object sender, FormClosedEventArgs e)
    this.Application.ActiveWindow.WindowState = Microsoft.Office.Interop.Word.WdWindowState.wdWindowStateNormal;


I have found this line always lies/returns true:


But this works better (global bool variable “AppActive” to keep track of active window):

//... VSTO Startup Event    
this.Application.WindowDeactivate += new Microsoft.Office.Interop.Word.ApplicationEvents4_WindowDeactivateEventHandler(Application_WindowDeactivate);
this.Application.WindowActivate += new Microsoft.Office.Interop.Word.ApplicationEvents4_WindowActivateEventHandler(Application_WindowActivate);

    void Application_WindowActivate(Microsoft.Office.Interop.Word.Document Doc, Microsoft.Office.Interop.Word.Window Wn)
        AppActive = true;

    void Application_WindowDeactivate(Microsoft.Office.Interop.Word.Document Doc, Microsoft.Office.Interop.Word.Window Wn)
        AppActive = false;


this.ActiveWindow.Activate() is the method that activates the window.

this.ActiveWindow.Active is the property that tell you the state of the window.