ElementHost flickers black borders on resize - wpf

Question

Disclaimer: This is not a duplicated post. I googled about the issue. Also read this, this and this SO questions. I tried some of those things but nothing seemed to help.
Consider the following simple example code. It's just an empty ElementHost inside a WinForm (no WPF control inside):
using System.Windows.Forms;
using System.Windows.Forms.Integration;
namespace WindowsFormsApplication15
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
ElementHost host = new ElementHost();
host.Dock = DockStyle.Fill;
this.Controls.Add(host);
}
}
}
When you resize the form, you can see two black edges at the form border:
Please, ¿someone could give a working solution over my example to fix this issue?

Answer 1

Try this (same idea as the first link you provided, but better performance):
public class ElementHost2 : ElementHost {
public ElementHost2() {
this.AutoSize = true;
}
public override Size GetPreferredSize(Size proposedSize) {
Form f = this.FindForm();
Size s = f.ClientSize;
return s;
}
private const uint WM_SETREDRAW = 0xB;
[DllImport("user32.dll")]
private static extern int SendMessage(IntPtr hWnd, uint Msg, int wParam, int lParam);
[DllImport("user32.dll")]
static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X, int Y, int cx, int cy, uint uFlags);
private const uint NOSIZE = 0x0001;
private const uint NOMOVE = 0x0002;
private const uint NOZORDER = 0x0004;
private const uint NOREDRAW = 0x0008;
private const uint NOACTIVATE = 0x0010;
private const uint DRAWFRAME = 0x0020;
private const uint FRAMECHANGED = 0x0020;
private const uint SHOWWINDOW = 0x0040;
private const uint HIDEWINDOW = 0x0080;
private const uint NOCOPYBITS = 0x0100;
private const uint NOOWNERZORDER = 0x0200;
private const uint NOREPOSITION = 0x0200;
private const uint NOSENDCHANGING = 0x0400;
private const uint DEFERERASE = 0x2000;
private const uint ASYNCWINDOWPOS = 0x4000;
protected override void OnResize(EventArgs e) {
base.OnResize(e);
SendMessage(this.Handle, WM_SETREDRAW, 0, 0);
SendMessage(this.Handle, WM_SETREDRAW, 1, 0);
// forces window to redraw:
SetWindowPos(this.Handle, IntPtr.Zero, 0, 0, 0, 0, NOSIZE | NOMOVE| NOZORDER | NOACTIVATE | SHOWWINDOW);
}
// better performance?
protected override void OnPaintBackground(PaintEventArgs pevent) {
//base.OnPaintBackground(pevent);
}
protected override void OnPaint(PaintEventArgs e) {
//base.OnPaint(e);
}
}
class Form2 : Form {
ElementHost host = new ElementHost2();
public Form2() {
Controls.Add(host);
this.BackColor = Color.Red;
var p = new System.Windows.Controls.DockPanel();
p.Background = System.Windows.Media.Brushes.Red;
host.Child = p;
p.Children.Add(new System.Windows.Controls.TextBox { Width = 100, Height = 20 });
}
}

Answer 2

The issue is not related to ElementHost and Winforms. It's just a WPF issue, and I found the answer in the following SO question:
How to fix the WPF form resize - controls lagging behind and black background?