public class Form1 : System.Windows.Forms.Form
{
 [DllImport("user32.dll",EntryPoint="GetSystemMenu")] //導入API函數
 extern static System.IntPtr GetSystemMenu(System.IntPtr hWnd , System.IntPtr bRevert);

 [DllImport("user32.dll",EntryPoint="RemoveMenu")]
 extern static int RemoveMenu (IntPtr hMenu, int nPos, int flags);
 static int MF_BYPOSITION = 0x400;
 static int MF_REMOVE = 0x1000;

 public Form1()//構造函數
 {
  InitializeComponent();
  RemoveMenu(GetSystemMenu(Handle,IntPtr.Zero),0,MF_BYPOSITION|MF_REMOVE);   
 }
}

//改變窗體風格，使之不能用鼠標拖拽改變大小
this.FormBorderStyle = FormBorderStyle.FixedSingle;

//禁止使用最大化按鈕
this.MaximizeBox = false;