.NET Information center: How do I prevent users from pinning my program to the taskbar?

Sunday, June 05, 2011

How do I prevent users from pinning my program to the taskbar?

A customer wanted to prevent users from pinning their application to the taskbar.

I have an application that is launched as a helper by a main application. Users shouldn't be launching it directly, but rather should be launching the main application. But since the helper shows up in the taskbar, users may be tempted to right-click on the taskbar icon and select "Pin to taskbar." Unfortunately, this pins the helper program to the taskbar instead of the main application, and launching the helper program directly doesn't work. Is there a way I can prevent users from pinning the helper program?

It so happens that there are a number of ways of marking your helper program as Don't pin me. Given the description above, the most direct way is probably to set the System.AppUserModel.PreventPinning property on the window created by the helper program.

Take our scratch program and make the following changes:

#include <shellapi.h>

#include <propsys.h>

#include <propkey.h>

HRESULT MarkWindowAsUnpinnable(HWND hwnd)

{

IPropertyStore *pps;

HRESULT hr = SHGetPropertyStoreForWindow(hwnd, IID_PPV_ARGS(&pps));

if (SUCCEEDED(hr)) {

PROPVARIANT var;

var.vt = VT_BOOL;

var.boolVal = VARIANT_TRUE;

hr = pps->SetValue(PKEY_AppUserModel_PreventPinning, var);

pps->Release();

}

return hr;

}

BOOL

OnCreate(HWND hwnd, LPCREATESTRUCT lpcs)

{

MarkWindowAsUnpinnable(hwnd);

return TRUE;

}

I set the PROPVARIANT manually instead of using InitPropVariantFromBoolean just to emphasize that the boolVal must be VARIANT_TRUE and not TRUE. In real life, I probably would have used InitPropVariantFromBoolean.