Save TreeView State

So for example, let's say you have a C# program that builds a TreeView programmatically. Since elements are dynamic, the TreeView is cleared and repopulated every time a single Node is changed.

Save TreeView State

The concept is simple: iterate through the top level Nodes of a TreeView and save whether the node was expanded or collapsed. Notice that to keep things simple, the source code only saves the state of top-level nodes:

 

private Dictionary<string, bool> SaveTreeState(TreeView tree)
{
     Dictionary<string, bool> nodeStates = new Dictionary<string, bool>();
     for (int i = 0; i < tree.Nodes.Count; i++)
     {
          if (tree.Nodes[i].Nodes.Count > 0)
          {
              nodeStates.Add(tree.Nodes[i].Name, tree.Nodes[i].IsExpanded);
          }
     }

     return nodeStates;
}

 

Load TreeView State

Once the TreeView state is saved, loading the state is just as simple:

 

private void RestoreTreeState(TreeView tree, Dictionary<string, bool> treeState)
{
     for (int i = 0; i < tree.Nodes.Count; i++)
     {
          if (treeState.ContainsKey(tree.Nodes[i].Name))
          {
              if (treeState[tree.Nodes[i].Name])
                  tree.Nodes[i].Expand();
              else
                  tree.Nodes[i].Collapse();
          }
     }
}

The C# functions Expand and Collapse make it simple to set the previous state of the TreeView nodes.