Windows API:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace BaseForm
{
    public partial class FormEnumlator : Form
    {
        public FormEnumlator()
        {
            InitializeComponent(); 
      
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
            this.SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.OptimizedDoubleBuffer, true);
            SetClassLong(this.Handle, GCL_STYLE, GetClassLong(this.Handle, GCL_STYLE) | CS_DropSHADOW); //API函式載入，實現窗體邊框陰影效果   
            Location = new Point(0,0);
            //  this.StartPosition = FormStartPosition.Manual;
        }

        private bool _IsMouseDown;
        private Point _oldLocation;
        private Point _startPoint;

        #region 窗體邊框陰影效果變數申明

        private const int CS_DropSHADOW = 0x20000;
        private const int GCL_STYLE = (-26);
        //宣告Win32 API
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern int SetClassLong(IntPtr hwnd, int nIndex, int dwNewLong);
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern int GetClassLong(IntPtr hwnd, int nIndex);

        #endregion


        protected override void OnLoad(EventArgs e)
        {
           // base.OnLoad(e);
        }

        private void frmEnumlator_Load(object sender, EventArgs e)
        {
           
        }
    }
}