可以在异步任务中更改前景色但不能更改文本框的背景色

Question

I'm trying to change colors of a textbox as stated above, I'm just gonna show the code because I think that would be the most fitting explanation.

    private async Task Disco()
    {
        int duration;
        switch (ptr)
        {
            default:
                //duration = 900;//15 min
                duration = 10;
                break;
            case 1:
                duration = 50;
                //duration = 1800;//30 min
                break;
        }

        int color = 0;
        await Task.Run(() =>
        {
            while (duration-- != 0)
            {
                TB.ForeColor = foreground[color];
                TB.BackColor = background[color];
                if (++color == foreground.Length)
                    color = 0;
                Thread.Sleep(1000);
            }
        });

        TB.ForeColor = Color.Black;
    }

The forecolor has been working fine, but when I added the backcolor line it throws

"An exception of type 'System.InvalidOperationException' occurred in System.Windows.Forms.dll but was not handled in user code Cross-thread operation not valid: Control 'TB' accessed from a thread other than the thread it was created on."

How is this even possible???

I'm literally accessing it in the line above with the forecolor, why is the backcolor behaving different???

If I make the backcolor line a comment everything is fine again....

Making a static var for the textbox does not help.

I am using .net 3.1(for win 7) but that should not be the problem here.

Answer 1

As hijinxbassist and MySkullCaveIsADarkPlace stated, I got lot lucky with the foreground and had to invoke the UI calls.