DoubleClick a TreeView Node?

j1e1g1

Update: I tried replacing "AfterSelect" with DoubleClick, but when I compile I get this error:"D:\Documents\Visual Studio Projects\WindowsApplication5\Form1.cs(70): Cannot implicitly convert type 'System.Windows.Forms.TreeViewEventHandler' to 'System.EventHandler' " from this line: "this.treeView1.DoubleClick += new System.Windows.Forms.TreeViewEventHandler(this.treeView1_DoubleClick);". I tried casting this.treeView1.DoubleCLick to a TreeViewEventHandler, but it won't let me do that either. Any suggestions? (sorry, I'm very new to C#) Also, would it be possible to change the event from DoubleClick to when the user presses the "Enter" key? If so, what is the event for this? Thanks, Justin Original Question: I am relativley new to C#, and I'm trying to write an app, using the compact framework, that will allow a handheld user to scroll through a treeview, hit enter on a selected node, and then do something specific to that node. I figured that the doubleclick event was as close as I could get to actually pressing enter/return, but I still cannot figure out how to write a method that is specific to a node of the treeview, rather than the entire treeview. When I doubleclick on the treeview in design mode, regardless of what node I click on, the only code it creates for me is private void treeView1_AfterSelect(...). So, does anyone know how to setup a function that will do something when the user doubleclicks/hits enter on a node of a treeview? Examples are much appreciated. Thanks, j1e1g1

Nick Parker

Take a look at the TreeView.AfterSelect Event[^] documentation on MSDN. The TreeViewEventArgs contain a Node which you can refer to within your method as the selected node.

private void TreeView1_AfterSelect(object sender, TreeViewEventArgs e)
{
//...
TreeNode node = e.Node;
if(node != null)
//...
}

- Nick Parker
My Blog | My Articles

Dave Kreskowiak

Since the TreeNode doesn't fire any everys, you can't wire up any code to it. The DoubleClick event is fired by the TreeView control, not the TreeNode you clicked on. In your DoubleClick event handler, you'll used the SelectedNode property to find out which node the used clicked on. You can modify the function that the designer creates by renaming the treeView1_AfterSelect function to treeView1_DoubleClick and making the same change in the Windows Forms Designer gnerated code section. A search and replace for "AfterSelect" ought to do it nicely. RageInTheMachine9532 "...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

j1e1g1

I tried replacing "AfterSelect" with DoubleClick, but when I compile I get this error:"D:\Documents\Visual Studio Projects\WindowsApplication5\Form1.cs(70): Cannot implicitly convert type 'System.Windows.Forms.TreeViewEventHandler' to 'System.EventHandler' " from this line: "this.treeView1.DoubleClick += new System.Windows.Forms.TreeViewEventHandler(this.treeView1_DoubleClick);". I tried casting this.treeView1.DoubleCLick to a TreeViewEventHandler, but it won't let me do that either. Any suggestions? (sorry, I'm very new to C#) Also, would it be possible to change the event from DoubleClick to when the user presses the "Enter" key? If so, what is the event for this? Thanks, Justin

Serge Lobko Lobanovsky

Hi, The solution depends on the treeview depth. If it finite and small (e.g. 3 fixed levels), you can write a function that will tell your program, what kind of node it clicked on based on its treeview position. If the depth is indeterminate, you can assign some kind of identity object to the TreeNode's Tag property to tell one node type from another. Regards, Serge (Logic Software, Easy Projects .NET site)

Dave Kreskowiak

Oooops... My mistake. That line should read:

this.treeView1.DoubleClick += new System.EventHandler(this.treeView1_DoubleClick);

There is no specific event fired for the Enter key. You might want to look into handling the KeyPress event, or KeyDown/KeyUp events, or possibly the Click event, to see which one will suit your needs. You can do this easily enough by displaying a MessageBox when those event fire. RageInTheMachine9532 "...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

Heath Stewart

Because DoubleClick is not of type TreeViewEventHandler, it is of type EventHandler, as the documentation would tell you if you read it. You can get the TreeNode that was double-clicked like so:

this.treeView1.DoubleClick += new EventHandler(treeView1_DoubleClick);
//...
private void treeView1_DoubleClick(object sender, EventArgs e)
{
Point p = PointToClient(MousePosition);
TreeNode node = GetNodeAt(p);
if (node != null)
{
// Do something with the TreeNode that was double-clicked.
}
}

If you want to use the Enter key instead (really, it's better to use both), then handle the KeyDown event and get the select node using the TreeView.SelectedNode property. If you want to know what events, methods, and properties are available for the TreeView, then you really should read the class documentation. See TreeView Members[^] in the .NET Framework SDK. The only true way to learn what all is available is to read.

Microsoft MVP, Visual C# My Articles

j1e1g1

This line: this.treeView1.DoubleClick += new System.EventHandler(this.treeView1_DoubleClick); Still throws an error, because I'm not passing this.treeView1_DoubleClick any parameters. I'm not sure what I should pass here, other than (?nulls), because I don't have a sender object or an event arg to pass it. Here is the error: Method 'WindowsApplication5.Form1.treeView1_DoubleClick(object, System.Windows.Forms.TreeViewEventArgs)' does not match delegate 'void System.EventHandler(object, System.EventArgs)' Sorry if this seems elementary, I'm still learning.. Thank you for your patience and your helpful responses, Justin

j1e1g1

I have looked at the SDK, but it is all still a little overwhelming to a new .Net programmer. I guess I just need more practice with the syntax and necessary declarations of form control objects. Also, its still throwing an error, because I'm not passing treeView1_DoubleClick any parameters in this line: this.treeView1.DoubleClick += new EventHandler(treeView1_DoubleClick); I'm not sure what sender object or event args I should pass here, since I'm really just initializing the DoubleClick event... Error:'WindowsApplication5.Form1.treeView1_DoubleClick(object, System.Windows.Forms.TreeViewEventArgs)' does not match delegate 'void System.EventHandler(object, System.EventArgs)' Thanks for your help and patience, Justin

Heath Stewart

j1e1g1 wrote: I have looked at the SDK, but it is all still a little overwhelming to a new .Net programmer. I guess I just need more practice with the syntax and necessary declarations of form control objects. It's not about syntax; it's about the classes available to a language (a "syntax"). The base class library (BCL) and any other class libraries for .NET are available to all managed languages like C#, VB.NET, etc. They call compile to Intermediate Language (IL), which is one of the features of the Common Language Infrastructure (CLI). The only way to learn all this is to read. You don't pass parameters to a delegate (your EventHandler) - the caller does. But the signature for the method has to match declaration of the delegate. Look at my code sample again; your treeView1_DoubleClick has to be declared as this:

private void treeView1_DoubleClick(object sender, EventArgs e)
{
//...
}

The important aspects of this method signature are in bold.

Microsoft MVP, Visual C# My Articles