C# – Change TreeNode image on expand-collapse events

ctreeviewwinforms

I have a treeView with many nodes. I want that some nodes change their image when node collapsed/expanded. How can I do it ?

Unfortunately, TreeNode don't have properties like ExpandNodeImage, CollapseNodeImage \

TreeView can change very often, so nodes can be deleted/added.. i can delete child nodes and so on…

Maybe, there is a class like ExpandAndCollapseNode ?

Best Answer

1). Add an ImageList Control to your WinForm.

2). Populate the ImageList with the pictures/icons you wish to change/display in response to what the user does at run-time with the TreeView, such as expanding, or collapsing nodes.

3). Assign the 'ImageList Control to the 'ImageList property of the 'TreeView

At this point you may want to make an initial pass over the TreeView, assuming it is populated, assigning the Node.ImageIndex property to point to the Image ... in the ImageList ... you want to use for the Node depending on whether it has children, or whatever.

4). If a user expands a Node, for example, you can use the BeforeExpand Event of the TreeView to change the Node's picture : like so : in this case we use the index of the Picture in the ImageList :

    private void treeView1_BeforeExpand(object sender, TreeViewCancelEventArgs e)
    {
        e.Node.ImageIndex = 3;
    }

5) You can also set the Node's image by using the ImageKey property which is the string name of the Image

6) There lots of other possible Node Picture variations to use : check out : SelectedImageIndex and SelectedImageKey : You can change Node pictures in the BeforeSelect, AfterSelect and BeforeExpand, events also, depending on the effect you are after.

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C# – Cross-thread operation not valid: Control accessed from a thread other than the thread it was created on

As per Prerak K's update comment (since deleted):

I guess I have not presented the question properly.

Situation is this: I want to load data into a global variable based on the value of a control. I don't want to change the value of a control from the child thread. I'm not going to do it ever from a child thread.

So only accessing the value so that corresponding data can be fetched from the database.

The solution you want then should look like:

UserContrl1_LOadDataMethod()
{
    string name = "";
    if(textbox1.InvokeRequired)
    {
        textbox1.Invoke(new MethodInvoker(delegate { name = textbox1.text; }));
    }
    if(name == "MyName")
    {
        // do whatever
    }
}

Do your serious processing in the separate thread before you attempt to switch back to the control's thread. For example:

UserContrl1_LOadDataMethod()
{
    if(textbox1.text=="MyName") //<<======Now it wont give exception**
    {
        //Load data correspondin to "MyName"
        //Populate a globale variable List<string> which will be
        //bound to grid at some later stage
        if(InvokeRequired)
        {
            // after we've done all the processing, 
            this.Invoke(new MethodInvoker(delegate {
                // load the control with the appropriate data
            }));
            return;
        }
    }
}

C# – Treeview prevent Node collapse

I stopped using the WinForms TreeView some time ago because of it's limits and quirks.

My favorite replacement is the open-source TreeViewAdv:

TreeViewAdv on Source Forge

TreeViewAdv on CodeProject

Best Answer

Related Solutions

C# – Cross-thread operation not valid: Control accessed from a thread other than the thread it was created on

C# – Treeview prevent Node collapse

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