Modifying opacity of any window from C#

Question

Is it possible to modify the opacity of all opened windows from C#. I googled for minimizing the windows and i came to know that its possible with pInvoke calls. It even worked. Similarly is it possible to change the opacity of all the opened windows from C#?

Also, i am not in to MFC stuffs. Still is there any tools to know the list of apis exposed in a dll?

Answer 1

You can use SetLayeredWindowAttributes API to do so.

Check this for the pInvoke version of this API.

Sample Code from the above-mentioned link:

[DllImport("user32.dll")]
static extern bool SetLayeredWindowAttributes(IntPtr hwnd, uint crKey,byte bAlpha, uint dwFlags);

public const int GWL_EXSTYLE = -20;
public const int WS_EX_LAYERED = 0x80000;
public const int LWA_ALPHA = 0x2;
public const int LWA_COLORKEY = 0x1;

//set the window style to alpha appearance
private void button4_Click(object sender, EventArgs e)
{
    SetWindowLong(Handle, GWL_EXSTYLE, GetWindowLong(Handle, GWL_EXSTYLE) ^ WS_EX_LAYERED);
    SetLayeredWindowAttributes(Handle, 0, 128, LWA_ALPHA);
}