[ListView.View=List]的垂直滚动条

该问题来自论坛提问，当ListView.View=List时，滚动条只能是水平的，解决这个问题需要子类化ListView处理WndProc消息，通过Windows API函数来设置它的滚动条。

演示代码：

using System;
using System.Drawing;
using System.Windows.Forms;
namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        /// <summary>
        /// 子类化ListView，在View属性是List的时候出垂直滚动条
        /// by jinjazz
        /// http://blog.csdn.net/jinjazz
        /// </summary>
        public class ListViewEx : ListView
        {
            [System.Runtime.InteropServices.DllImport("user32.dll")]
            public static extern int ShowScrollBar(IntPtr hWnd, int iBar, int bShow);
            const int SB_HORZ = 0;
            const int SB_VERT = 1;
            protected override void WndProc(ref Message m)
            {
                if (this.View == View.List)
                {
                    ShowScrollBar(this.Handle, SB_VERT, 1);
                    ShowScrollBar(this.Handle, SB_HORZ, 0);
                }
                base.WndProc(ref m);
            }
        }
        
        /// <summary>
        /// 测试代码
        /// </summary>
        public Form1()
        {
            InitializeComponent();
            //测试普通listview
            ListView list = new ListView();
            list.View = View.List;
            this.Controls.Add(list);
            list.Size = new Size(100, 100);
            list.Location = new Point(100, 100);
            for (int i = 0; i < 100; i++)
            {
                list.Items.Add(new ListViewItem(Guid.NewGuid().ToString()));
            }
            //测试子类化的listview
            list = new ListViewEx();
            list.View = View.List;
            this.Controls.Add(list);
            list.Size = new Size(100, 100);
            list.Location = new Point(300, 100);
            for (int i = 0; i < 100; i++)
            {
                list.Items.Add(new ListViewItem(Guid.NewGuid().ToString()));
            }
        }
       
    }
}