CodeMatrix/CodeMatrix/Utils/FormHelper.cs

using System;
using System.Runtime.InteropServices;

namespace CodeMatrix.Utils
{
    public static class FormHelper
    {
        [DllImport("user32.dll")]
        static extern bool ReleaseCapture();

        [DllImport("user32.dll")]
        static extern bool SendMessage(IntPtr hwnd, int wMsg, int wParam, int lParam);

        const int WM_SYSCOMMAND = 0x0112;
        const int SC_MOVE = 0xF010;
        const int HTCAPTION = 0x0002;

        public static void OnMouseDown(IntPtr handle)
        {
            ReleaseCapture();
            SendMessage(handle, WM_SYSCOMMAND, SC_MOVE | HTCAPTION, 0);
        }

        const int CS_DropSHADOW = 0x20000;
        const int GCL_STYLE = -26;

        static IntPtr SetClassLong(IntPtr hWnd, int nIndex, IntPtr dwNewLong)
        {
            if (IntPtr.Size > 4)
                return SetClassLongPtr64(hWnd, nIndex, dwNewLong);
            else
                return new IntPtr(SetClassLongPtr32(hWnd, nIndex, unchecked((uint)dwNewLong.ToInt32())));
        }

        [DllImport("user32.dll", EntryPoint = "SetClassLong")]
        static extern uint SetClassLongPtr32(IntPtr hWnd, int nIndex, uint dwNewLong);

        [DllImport("user32.dll", EntryPoint = "SetClassLongPtr")]
        static extern IntPtr SetClassLongPtr64(IntPtr hWnd, int nIndex, IntPtr dwNewLong);
        static IntPtr GetClassLongPtr(IntPtr hWnd, int nIndex)
        {
            if (IntPtr.Size > 4)
                return GetClassLongPtr64(hWnd, nIndex);
            else
                return new IntPtr(GetClassLongPtr32(hWnd, nIndex));
        }

        [DllImport("user32.dll", EntryPoint = "GetClassLong")]
        static extern uint GetClassLongPtr32(IntPtr hWnd, int nIndex);

        [DllImport("user32.dll", EntryPoint = "GetClassLongPtr")]
        static extern IntPtr GetClassLongPtr64(IntPtr hWnd, int nIndex);


        public static void EnableFromDropShadow(IntPtr handle)
        {
            SetClassLong(handle, GCL_STYLE, (IntPtr)((long)GetClassLongPtr(handle, GCL_STYLE) | CS_DropSHADOW));
        }
    }
}