让顶层窗体不无激活但能正常使用

http://blog.csdn.net/thirdapple/article/details/2755684

附件 http://files.cnblogs.com/xe2011/CSharpWinForm_WM_NCACTIVATE.rar

这个效果就像 你单击Combobox 下拉按钮或者菜单 主窗体不会失去焦点一样

Form1

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;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Form2 f = new Form2();
            f.TopMost = true;
            f.Show();
        }
    }
}

Form2

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;

namespace WindowsFormsApplication1
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }


        [System.Runtime.InteropServices.DllImport("user32.dll")]
        private extern static IntPtr SetActiveWindow(IntPtr handle);
        private const int WM_ACTIVATE = 0x006;
        private const int WM_ACTIVATEAPP = 0x01C;
        private const int WM_NCACTIVATE = 0x086;
        private const int WA_INACTIVE = 0;
        private const int WM_MOUSEACTIVATE = 0x21;
        private const int MA_NOACTIVATE = 3;
        protected override void WndProc(ref Message m)
        {
            if (m.Msg == WM_MOUSEACTIVATE)
            {
                m.Result = new IntPtr(MA_NOACTIVATE);
                return;
            }
            else if (m.Msg == WM_NCACTIVATE)
            {
                
                if (((int)m.WParam & 0xFFFF) != WA_INACTIVE)
                {
                    if (m.LParam != IntPtr.Zero)
                        SetActiveWindow(m.LParam);
                    else
                        SetActiveWindow(IntPtr.Zero);
                    return;
                }
               
            }
            base.WndProc(ref m);
        }

    }
}