Question

In Microsoft Access there was an easy method to turn off screen updates by setting Echo = False. Is there an equivalent in VB.NET for WinForms? I’ve got a situation where I’m trying to prevent users from seeing controls flickering while they’re being updated. I could probably solve the problem by coding it differently, but would rather avoid it if I can.

Answer 1

What you’re looking to do is suspend and resume the redrawing of your form. There isn’t a managed API for this, but it’s a fairly trivial P/Invoke to do it. I don’t remember the VB.NET syntax for declaring external functions right off the top of my head, but this C# example should give you the information that you need to know.

[DllImport("user32.dll")]
public static extern int SendMessage(IntPtr hWnd, Int32 wMsg, bool wParam, Int32 lParam);

private const int WM_SETREDRAW = 11; 

public static void SuspendDrawing(Control target)
{
    SendMessage(target.Handle, WM_SETREDRAW, false, 0);
}

public static void ResumeDrawing(Control target)
{
    SendMessage(target.Handle, WM_SETREDRAW, true, 0);
    target.Refresh();
}