TreeView - Node not expanding

问题

I have a TreeView with several nodes and if a special node (you will see in code) is deleted, the parent node should be expanded after updating the TreeView.

Here's how I tried it:

public void Remove(){
    ...
    ...
    else if ((NodeType)n.Tag == NodeType.Attribute) //Here I simply check if it's the "special" parent
    {
       Commands.CommandAttributeRemove cmd = (Commands.CommandAttributeRemove)mAppData.CommandFactory.Create("AttributeRemove");
       cmd.Data = n.Text;
       cmd.ObjectClass = mObjectClass;
       cmd.ObjectTypeName = n.Parent.Parent.Text;
       list.Add(cmd);
       mNodeToExpand = mTreeView.SelectedNode.Parent; //THIS LINE IS IMPORTANT... mNodeToExpand is a member variable which I use in UpdateData()
    }
    ...
    ...
    UpdateData();
}

public void UpdateData()
    {
       … //A lot of not so important stuff happening here (at least not important for what I want, I think)
       ...
        //Update Selected Items (for the case that objects were deleted) and UpdateSelection
        OnSelect();

        //UpdateSelection();
        this.Update();

Now that's interesting stuff:

   if (mNodeToExpand != null)
        {
            mNodeToExpand.Expand();
            mNodeToExpand = null;
        }
}

This is how I tried to achieve what I want, but the node doesn't expand (it still has other children).

In the Remove() I also tried mTreeView.SelectedNode.Parent.Nodes.Add(new Node("Blabla")); but it doesn't even add a node.

And in the if(mNodeToExpand!=null) I also try to set the selectedNode to mNodeToExpand, but it gives me a NullReferenceException EVEN THOUGH I CHECK IF IT'S NULL IN THE IF. WHY?

回答1:

This can't freaking be it. FullPath is apparently the path of the node in the treeview, so for example if you have Node2 which is a sub-node of Node1, then the FullPath of Node1 is "Node1" and of Node2 "Node1//Node2" … Now the thing is that FOR SOME WEIRD REASON my mNodeToExpand loses the Information of FullPath and suddenly it's only "Node2" instead of "Node1//Node2"... Because of that it isn't expanded cause the TreeView doesn't find a node with this FullPath… Now what I did is that I stored the FullPath in a string and when I want to expand it I search for the node with this FullPath and then expand what is returned. This is so stupid, cause imagine a list of 1 000 000 nodes. This could take very long. I'm starting to really dislike this Crownwoods.DotNetMagic library but it's already existing Code I'm working on.

来源：https://stackoverflow.com/questions/51519226/treeview-node-not-expanding