how to find all directories in all local machine ?

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C#

.NET

Hi all,
I want to automatically find all directories in a local machine using c#.
I have done this with the code shown below, which should select a node to find sub directory and I want to do this automatically.

Can anyone help me?

private void button2_Click(object sender, EventArgs e)
{

            DriveInfo[] varDriveInfo = DriveInfo.GetDrives();

            string[] SubElement = new string[varDriveInfo.Length];
            TreeNode trd=new TreeNode();
            for (int i = 0; i < varDriveInfo.Length; i++) 
            {
                trd.Nodes.Add(varDriveInfo[i].ToString().Substring(0, 1));

                treeView1.Nodes.Add(varDriveInfo[i].ToString().Substring(0, 1));
                try
                {
                    string[] subDirectory = Directory .GetDirectories (varDriveInfo[i] .ToString());
                    for (int j = 0; j < subDirectory.Length; j++)
                    {
                        treeView1.Nodes[i].Nodes.Add(subDirectory[j]);
                    }
                }
                catch
                { continue; }
            }
            
        }

code for find sub directory :

private void treeView1_AfterSelect(object sender, TreeViewEventArgs e)
 {
     try
     {
         string[] subDirectory = Directory.GetDirectories(treeView1.SelectedNode.Text);

         string[] ListFile = Directory.GetFiles(treeView1.SelectedNode.Text);

         listBox1.Items.Clear();

         foreach (string FileName in ListFile)
             listBox1.Items.Add(FileName);

         for (int j = 0; j < subDirectory.Length; j++)
             try
             {
                 treeView1.SelectedNode.Nodes.Add(subDirectory[j]);
             }


             catch
             { continue; }
     }
     catch { }

 }

[Edit - Spelling, grammar, and added code block]