How to set opacity of a window?

[Daniel Chylek]

Hi, I want to set opacity of a window.

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;
static void Main(string[] args){
IntPtr Handle = Process.GetCurrentProcess().MainWindowHandle;
Console.WriteLine(SetWindowLong(Handle,GWL_EXSTYLE,(int)GetWindowLong(Handle, GWL_EXSTYLE) ^ WS_EX_LAYERED));
Console.WriteLine(Marshal.GetLastWin32Error());
Console.WriteLine(SetLayeredWindowAttributes(Handle,0,64,LWA_ALPHA));
Console.WriteLine(Marshal.GetLastWin32Error());
Console.ReadKey();
}
 

And this is output:
0 (SetWindowLong() failed)
1008 (ERROR_NO_TOKEN)
False (SetLayeredWindowAttributes() failed)
87 (ERROR_INVALID_PARAMETER)

I tried to find a solution, but I didn't find anything, please help me. (Of course I imported functions from user32.dll, and sorry if I made mistakes in text, I'm still learning English)

[Plater]

Couln't you just use this line:
this.Opacity = .5;

That sets my window to 50% opacity

[Daniel Chylek]

Sorry, I didn't formulate what I need. I want to set opacity of variable "Handle" into which I will insert window handle later. Now it's set to the current process for testing.

[Plater]

Ahhh, looking back at your code...
Do you even HAVE a handle to work with? It doesn't look like you have any forms open at the time of running the code?

EDIT:
I just ran it and the line: Process.GetCurrentProcess().MainWindowHandle;
always returned a zero, even when I had a main window.
I was successfull with this though:

IntPtr Handle = this.Handle;
Int32 oldValue = GetWindowLong(Handle, GWL_EXSTYLE);
Int32 AlsoOldValue = SetWindowLong(Handle, GWL_EXSTYLE, oldValue | WS_EX_LAYERED);
bool result=SetLayeredWindowAttributes(Handle, 0, 255 / 2, LWA_ALPHA);
 

It also worked when I used the Process object to get the MainWindowHandle of a different process and set THAT window's opacity

[Daniel Chylek]

Thanks, it works! I will try to make fade-in and fade-out effect :).