using System; using System.Windows.Forms; using System.Runtime.InteropServices; namespace WindowsApplication43 {   public partial class Form1 : Form   {     Form frm =null;     public Form1()     {       InitializeComponent();       this.Activated += Form_Activated;     }     const int WM_NCACTIVATE = 0x86;     const int WA_ACTIVE = 0x1;     [DllImport("user32.dll", EntryPoint = "SendMessage")]     public static extern int SendMessage(IntPtr hWnd, int wMsg, int wParam, int lParam);     private void button1_Click(object sender, EventArgs e)     {       frm = new Form();       frm.Text = "jinjazz";       frm.Activated += Form_Activated;       frm.Show();       frm.Location = new System.Drawing.Point(this.Left + this.Width, this.Top);       SendMessage(this.Handle, WM_NCACTIVATE, WA_ACTIVE, 0);     }     void Form_Activated(object sender, EventArgs e)     {        SendMessage(this.Handle, WM_NCACTIVATE, WA_ACTIVE, 0);        if (frm != null)          SendMessage(frm.Handle, WM_NCACTIVATE, WA_ACTIVE, 0);     }   } }