如何在C#中创建上下文菜单

我现在的代码导致主窗体闪烁.

private void treeView1_MouseDown(object sender,MouseEventArgs e)
{
    if (e.Button == MouseButtons.Right)
    {
        var myForm = new Form {Text = "My Form"};
        myForm.SetBounds(10,10,200,200);

        myForm.Show();
        // Determine if the form is modal.
        if (myForm.Modal == false)
        {
            // Change borderstyle and make it not a top level window.
            myForm.FormBorderStyle = FormBorderStyle.FixedToolWindow;
            myForm.TopLevel = false;
        }
    }            
}