给窗体做遮罩（另类做法）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace LUserControl
{
    public class TransparentBase : Form
    {
        /// <summary>
        /// 遮罩窗体
        /// </summary>
        public FrmTransparent FrmTran;
    }
}

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 LUserControl
{
    public partial class FrmTransparent : Form
    {
        /// <summary>
        /// 显示窗体
        /// </summary>
        public TransparentBase frm;
        /// <summary>
        /// 主窗体
        /// </summary>
        public Form MainFrm;
        public FrmTransparent()
        {
            InitializeComponent();
            TransparencyKey = Color.White;
        }

        private void LoadData()
        {
            frm.FrmTran = this;
            frm.StartPosition = FormStartPosition.CenterScreen;
            frm.ShowDialog();
        }

        private void FrmTransparent_Load(object sender, EventArgs e)
        {
            LoadData();
        }
    }
}

用法：

 FrmNoClose frmNoClose = new FrmNoClose();
                //equipmentLstForm.smallCabinetCode = cd.Name;
                //equipmentLstForm.totalNum = cd.SavedNum;
                //equipmentLstForm.storedNum = cd.SavingNum;
                frmNoClose.Cabinet = cd;
                //frmNoClose.ShowDialog();
                FrmTransparent frmTransparent = new FrmTransparent();
                frmTransparent.frm = frmNoClose;
                frmTransparent.MainFrm = this;
                frmTransparent.ShowDialog();

FrmNoClose必须继承TransparentBase类