Avoiding duplicate icon resources in a .NET (C#) project

You're looking for Icon.ExtractAssociatedIcon. Call passing your executable:

var icon = Icon.ExtractAssociatedIcon(Assembly.GetExecutingAssembly().Location);

I think in many cases including a duplicate icon is at the end of the day more efficient than trying to extract it from the unmanaged resource - considering you can't use Icon.ExtractAssociatedIcon for UNC paths.

Yeah, it's pretty annoying. But the problem with the proposed answer of Icon.ExtractAssociatedIcon is that it will retrieve the 32x32 icon, and then downsample to a 16x16 icon in your forms window or on the taskbar, which will look terrible unless your 32x32 icon is very cleverly constructed.

The way I'm doing it is with interop (put the first line in your form constructor):

this.Icon = ExtractSmallIconFromLibrary(Application.ExecutablePath);
...

public static Icon ExtractSmallIconFromLibrary(string file) {
    IntPtr[] reficon = new IntPtr[1];
    int nextracted = ExtractIconEx(file, 0, null, reficon, 1);
    if (nextracted < 1)
        return null;
    Icon unmanaged_icon = Icon.FromHandle(reficon[0]);
    Icon icon = (Icon)unmanaged_icon.Clone();
    DestroyIcon(unmanaged_icon.Handle);
    return icon;
}

[DllImport("Shell32", CharSet = CharSet.Auto)]
extern static int ExtractIconEx(
    [MarshalAs(UnmanagedType.LPTStr)] 
    string lpszFile,
    int nIconIndex,
    IntPtr[] phIconLarge,
    IntPtr[] phIconSmall,
    int nIcons
    );

[DllImport("user32.dll", CharSet = CharSet.Auto)]
extern static bool DestroyIcon(IntPtr handle);

But this isn't great, either, since you do want the 32x32 icon for things like the Alt-Tab icon list. So you really need to extract the entire icon, which is a bigger job. Maybe there's a straightforward way to combine the two icons into one. Or you can do like this codeproject program, which extracts the whole icon in the first place with a huge pile of code.

You're right, and it's rather annoying.

You have to load the icons yourself instead of relying on designer-generated code. Save the icon as a project resource, then load the resource into the form's Icon property in the form's constructor:

this.Icon = Properties.Resources.myIconResourceName;