在Winform中实现半透明遮罩层

效果图如下，正常时：



遮罩时：



控件代码：

using System;
using System.Collections.Generic;
using System.Text;
using System.Drawing;
using System.Windows.Forms;
using System.ComponentModel;

namespace MyOpaqueLayer
{

[ToolboxBitmap(typeof(MyOpaqueLayer))]
public class MyOpaqueLayer : System.Windows.Forms.Control
{
private bool _transparentBG = true;
private int _alpha = 125;

private System.ComponentModel.Container components = new System.ComponentModel.Container();

public MyOpaqueLayer()
: this(125, true)
{

}

public MyOpaqueLayer(int Alpha, bool showLoadingImage)
{
SetStyle(System.Windows.Forms.ControlStyles.Opaque, true);
base.CreateControl();
this._alpha = Alpha;
;
if (showLoadingImage)
{
PictureBox pictureBox_Loading = new PictureBox();
pictureBox_Loading.BackColor = System.Drawing.Color.White;
pictureBox_Loading.Image = global::MyOpaqueLayer.Properties.Resources.loading;
pictureBox_Loading.Name = "pictureBox_Loading";
pictureBox_Loading.Size = new System.Drawing.Size(48, 48);
pictureBox_Loading.SizeMode = System.Windows.Forms.PictureBoxSizeMode.AutoSize;
Point Location = new Point(this.Location.X + (this.Width - pictureBox_Loading.Width) / 2, this.Location.Y + (this.Height - pictureBox_Loading.Height) / 2);
pictureBox_Loading.Location = Location;
pictureBox_Loading.Anchor = AnchorStyles.None;
this.Controls.Add(pictureBox_Loading);
}
}

protected override void Dispose(bool disposing)
{
if (disposing)
{
if (!((components == null)))
{
components.Dispose();
}
}
base.Dispose(disposing);
}

/// <summary>
/// 自定义绘制窗体
/// </summary>
/// <param name="e"></param>
protected override void OnPaint(System.Windows.Forms.PaintEventArgs e)
{
float vlblControlWidth;
float vlblControlHeight;

Pen labelBorderPen;
SolidBrush labelBackColorBrush;

if (_transparentBG)
{
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);
}
base.OnPaint(e);
vlblControlWidth = this.Size.Width;
vlblControlHeight = this.Size.Height;
e.Graphics.DrawRectangle(labelBorderPen, 0, 0, vlblControlWidth, vlblControlHeight);
e.Graphics.FillRectangle(labelBackColorBrush, 0, 0, vlblControlWidth, vlblControlHeight);

}
/// <summary>
///
/// </summary>
protected override CreateParams CreateParams//v1.10
{
get
{
CreateParams cp = base.CreateParams;
cp.ExStyle |= 0x20; // 开启 WS_EX_TRANSPARENT,使控件支持透明
return cp;
}
}

[Category("myOpaqueLayer"), Description("是否使用透明,默认为True")]
public bool TransparentBG
{
get { return _transparentBG; }
set
{
_transparentBG = value;
this.Invalidate();
}
}

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

}

}

源码下载：

遮罩层源码