recursive SuspendDrawing and ResumeDrawing

Pilz.UI/Utilities/DrawingControl.vb

@@ -1,4 +1,4 @@
-Imports System.Runtime.CompilerServices
+Imports System.Runtime.CompilerServices
 Imports System.Windows.Forms
 
 Namespace Utils
@@ -6,10 +6,19 @@ Namespace Utils
     Public Module DrawingControl
 
         Private Const WM_SETREDRAW = 11
+        Private ReadOnly dicSuspendCount As New Dictionary(Of IntPtr, Integer)
 
         <Extension>
         Public Sub SuspendDrawing(control As Control)
-            SendMessage(control.Handle, WM_SETREDRAW, False, 0)
+            If Not dicSuspendCount.ContainsKey(control.Handle) Then
+                dicSuspendCount.Add(control.Handle, 1)
+            Else
+                dicSuspendCount(control.Handle) += 1
+            End If
+
+            If dicSuspendCount(control.Handle) = 1 Then
+                SendMessage(control.Handle, WM_SETREDRAW, False, 0)
+            End If
         End Sub
 
         <Extension>
@@ -19,8 +28,19 @@ Namespace Utils
 
         <Extension>
         Public Sub ResumeDrawing(control As Control, redraw As Boolean)
-            SendMessage(control.Handle, WM_SETREDRAW, True, 0)
+            Dim doRedraw As Boolean = True
-            If redraw Then control.Refresh()
+
+            If dicSuspendCount.ContainsKey(control.Handle) Then
+                dicSuspendCount(control.Handle) -= 1
+                If dicSuspendCount(control.Handle) >= 1 Then
+                    doRedraw = False
+                End If
+            End If
+
+            If doRedraw Then
+                SendMessage(control.Handle, WM_SETREDRAW, True, 0)
+                If redraw Then control.Refresh()
+            End If
         End Sub
 
     End Module