Code:

private void frmTreeView_Load(object sender, EventArgs e)
{
            treeView1.Nodes.Add("");
            treeView1.Nodes[0].Text= "Database";// this isparent node
            // fallowing are the child node of 'Database'
            treeView1.Nodes[0].Nodes.Add("sql server");
         
  treeView1.Nodes[0].Nodes.Add("my sql");
            treeView1.Nodes.Add("");
            treeView1.Nodes[1].Text
= "Programming Language";// this is parent node
            // fallowing are the child node of 'Programming Language'
            treeView1.Nodes[1].Nodes.Add("C#");
            treeView1.Nodes[1].Nodes.Add("J#");
            treeView1.Nodes[1].Nodes.Add("java");
}

Run the project

When you expand the Database node then child node of database will show .

TreeView Properties

ShowRootLine: set the ShowRootLine to show or hide Line, by default it is true.

ForeColor:  ForeColor of TreeView can be changed through TreeView ForeColor property.

Example:

private void frmTreeView_Load(object sender, EventArgs e)
{
            //change forecolor of treeview
            treeView1.ForeColor= Color.Red;
}

BackColor: BackColor of TreeView can be changed through TreeView BackColor property.

Example:

private void frmTreeView_Load(object sender, EventArgs e)
{
            //Change BackColor of TreeView 
            treeView1.BackColor = Color.CadetBlue;
}