Populating TreeViews with data acquired from void static callback methods
-
Hi, I'm trying to populate a TreeView with info I'm gathering via a PeekCompleted callback for a MessageQueue. My PeekCompleted method, which is "void static", does not have any trouble populating a ListBox but the compiler complains that I must use Control.Invoke() from the callback to use TreeNode.Add(). Here are my questions: 1) Why? 2) Should I use Control.Invoke() or do this another way? All I'm trying to do is build a TreeView using data I collected from a callback method. What are my other options? TIA, Matt
-
Hi, I'm trying to populate a TreeView with info I'm gathering via a PeekCompleted callback for a MessageQueue. My PeekCompleted method, which is "void static", does not have any trouble populating a ListBox but the compiler complains that I must use Control.Invoke() from the callback to use TreeNode.Add(). Here are my questions: 1) Why? 2) Should I use Control.Invoke() or do this another way? All I'm trying to do is build a TreeView using data I collected from a callback method. What are my other options? TIA, Matt
Yes you should use
Control.Invoke. This invokes the call on the thread on which the control was created, which is important. You should do this for yourListViewas well. Modifying the control from a different thread causes problems in the message queue. The technical details get down into what is encapsulated by the .NET Framework (much of it, anyway): Win32 APIs. To useInvoke, take a look at this sample code to safely add aTreeNodein the property thread:internal void SafeAdd(TreeNodeCollection nodes, TreeNode node)
{
if (nodes == null || node == null)
throw new ArgumentNullException(nodes == null ? "nodes" : "node");
if (treeView1.InvokeRequired)
{
Delegate d = new AddTreeNodeHandler(nodes.Add);
treeView1.Invoke(d, new object[] {node});
}
else nodes.Add(node);
}
private delegate int AddTreeNodeHandler(TreeNode node);Microsoft MVP, Visual C# My Articles