透明的加载等待层

在稍微复杂的交互应用中，避免不了耗时的操作，这时候总希望给用户明确的提示，表示程序在运行中暂时不能进行其他操作。显示一个半透明的处于等待状态的遮罩层是很好的方法。在Web应用程序中直接设置Div的透明度然后覆盖操作界面就好，但是Winform的好像并没有提供透明度之类的属性。

1.自定义控件类的实现

using System;
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{

    /// <summary>
    /// 透明的加载等待层
    /// </summary>
    [ToolboxBitmap(typeof(LoadingPanel))]
    public class LoadingPanel : Control
    {
        #region Field

        /// <summary>
        /// 是否背景透明
        /// </summary>
        private bool _transparentBackGround = true;

        /// <summary>
        /// 透明度
        /// </summary>
        private int _alpha = 125;

        /// <summary>
        /// 容器组件
        /// </summary>
        private readonly Container _components = new Container();

        #endregion

        #region Property

        /// <summary>
        /// 是否使用透明
        /// </summary>
        [Category("AlphaOpaque"), Description("是否使用透明,默认为True")]
        public bool TransparentBackGround
        {
            get { return _transparentBackGround; }
            set
            {
                _transparentBackGround = value;
                this.Invalidate();
            }
        }

        /// <summary>
        /// 设置透明度
        /// </summary>
        [Category("AlphaOpaque"), Description("设置透明度")]
        public int Alpha
        {
            get { return _alpha; }
            set
            {
                _alpha = value;
                this.Invalidate();
            }
        }

        #endregion

        #region Ctor

        /// <summary>
        /// 构造函数
        /// </summary>
        public LoadingPanel() : this(true) { }

        /// <summary>
        /// 标准构造函数
        /// </summary>
        /// <param name="showLoadingImage"></param>
        public LoadingPanel(bool showLoadingImage)
        {
            SetStyle(ControlStyles.Opaque | ControlStyles.AllPaintingInWmPaint | ControlStyles.UserPaint, true);

            base.CreateControl();
            // 显示等待的图像
            if (showLoadingImage)
            {
                var pictureBoxLoading = new PictureBox();
                pictureBoxLoading.BackColor = Color.White;
                pictureBoxLoading.Image = Properties.Resources.loding;
                pictureBoxLoading.Name = "pictureBox_Loading";
                pictureBoxLoading.Size = new Size(48, 48);
                pictureBoxLoading.SizeMode = PictureBoxSizeMode.Zoom;
                var location = new Point(this.Location.X + (this.Width - pictureBoxLoading.Width) / 2, 
                    this.Location.Y + (this.Height - pictureBoxLoading.Height) / 2);
                pictureBoxLoading.Location = location;
                pictureBoxLoading.Anchor = AnchorStyles.None;
                this.Controls.Add(pictureBoxLoading);
            }
        }

        #endregion

        #region Override Method

        /// <summary>
        /// 自定义绘制窗体
        /// </summary>
        /// <param name="e"></param>
        protected override void OnPaint(PaintEventArgs e)
        {
            Pen labelBorderPen;
            SolidBrush labelBackColorBrush;

            if (_transparentBackGround)
            {
                Color drawColor = Color.FromArgb(this._alpha, this.BackColor);
                labelBorderPen = new Pen(drawColor, 0);
                labelBackColorBrush = new SolidBrush(drawColor);
            }
            else
            {
                labelBorderPen = new Pen(this.BackColor, 0);
                labelBackColorBrush = new SolidBrush(this.BackColor);
            }

            float controlWidth = this.Size.Width;
            float controlHeight = this.Size.Height;

            e.Graphics.DrawRectangle(labelBorderPen, 0, 0, controlWidth, controlHeight);
            e.Graphics.FillRectangle(labelBackColorBrush, 0, 0, controlWidth, controlHeight);

            base.OnPaint(e);
        }

        /// <summary>
        /// 析构处理
        /// </summary>
        /// <param name="disposing"></param>
        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                if (_components != null)
                {
                    _components.Dispose();
                }
            }
            base.Dispose(disposing);
        }

        #endregion

        #region Public method

        /// <summary>
        /// 隐藏处理
        /// </summary>
        internal void CloseWaitingPanel()
        {
            this.BeginInvoke(new Action(() =>
            {
                SendToBack();
                Hide();
            }));
        }

        /// <summary>
        /// 显示处理
        /// </summary>
        internal void ShowWaitingPanel()
        {
            this.BeginInvoke(new Action(() =>
            {
                BringToFront();
                Show();
            }));
        }

        #endregion
    }
}

2.在窗体引用遮罩类达到理想的效果

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        private readonly LoadingPanel _loadingPanel;

        public Form1()
        {
            InitializeComponent();

            _loadingPanel = new LoadingPanel();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
           _loadingPanel.Dock = DockStyle.Fill;
            _loadingPanel.Hide();
           Controls.Add(_loadingPanel);
        }

        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            Thread.Sleep(10 * 1000);
        }

        private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            _loadingPanel.CloseWaitingPanel();
        }

        private void btnLoad_Click(object sender, EventArgs e)
        {
            if (!backgroundWorker1.IsBusy)
            {
                _loadingPanel.ShowWaitingPanel();

                backgroundWorker1.RunWorkerAsync();
            }
        }

    }
}

可以参考实现的效果，当单击按钮时，遮罩层显示半透明样式显示以遮挡用户操作。当后台操作结果时，遮罩层消失，用户继续其他操作。