最近在做卡片视图的程序，要求将控件做成带有圆角的效果，下面是我在网上查找的资料，经过测试，确定可以实现功能。其中方法三既适应于控件，也适应于窗体。

先上传效果图：

方法一：

增加命名空间:using System.Drawing.Drawing2D;
添加方法如下:当然各角的点可根据需要确定.
复制代码 代码如下:
private void Type(Control sender, int p_1, double p_2)
{
GraphicsPath oPath = new GraphicsPath();
oPath.AddClosedCurve(
new Point[] {
new Point(0, sender.Height / p_1),
new Point(sender.Width / p_1, 0),
new Point(sender.Width - sender.Width / p_1, 0),
new Point(sender.Width, sender.Height / p_1),
new Point(sender.Width, sender.Height - sender.Height / p_1),
new Point(sender.Width - sender.Width / p_1, sender.Height),
new Point(sender.Width / p_1, sender.Height),
new Point(0, sender.Height - sender.Height / p_1) },

(float)p_2);

sender.Region = new Region(oPath);
}

在窗体的paint和resize事件中增加:Type(this,20,0.1);
参数20和0.1也可以根据自己的需要调整到最佳效

方法二：
复制代码 代码如下:
public void SetWindowRegion()
{

System.Drawing.Drawing2D.GraphicsPath FormPath;

FormPath = new System.Drawing.Drawing2D.GraphicsPath();

Rectangle rect = new Rectangle(0, 22, this.Width, this.Height - 22);//this.Left-10,this.Top-10,this.Width-10,this.Height-10);

FormPath = GetRoundedRectPath(rect, 30);

this.Region = new Region(FormPath);

}

private GraphicsPath GetRoundedRectPath(Rectangle rect, int radius)
{

int diameter = radius;

Rectangle arcRect = new Rectangle(rect.Location, new Size(diameter, diameter));

GraphicsPath path = new GraphicsPath();

// 左上角

path.AddArc(arcRect, 180, 90);

// 右上角

arcRect.X = rect.Right - diameter;

path.AddArc(arcRect, 270, 90);

// 右下角

arcRect.Y = rect.Bottom - diameter;

path.AddArc(arcRect, 0, 90);

// 左下角

arcRect.X = rect.Left;

path.AddArc(arcRect, 90, 90);

path.CloseFigure();

return path;

}

在窗体的resize事件中增加:SetWindowRegion();

方法三：通过Window系统API行数，修改控件和窗体为椭圆形状。代码如下所示：

复制代码 代码如下:
[System.Runtime.InteropServices.DllImport("gdi32")]
private static extern IntPtr BeginPath(IntPtr hdc);
[System.Runtime.InteropServices.DllImport("gdi32")]
private static extern int SetBkMode(IntPtr hdc, int nBkMode);
const int TRANSPARENT = 1;
[System.Runtime.InteropServices.DllImport("gdi32")]
private static extern IntPtr EndPath(IntPtr hdc);
[System.Runtime.InteropServices.DllImport("gdi32")]
private static extern IntPtr PathToRegion(IntPtr hdc);
[System.Runtime.InteropServices.DllImport("gdi32")]
private static extern int Ellipse(IntPtr hdc, int x1, int y1, int x2, int y2);
[System.Runtime.InteropServices.DllImport("user32")]
private static extern IntPtr SetWindowRgn(IntPtr hwnd, IntPtr hRgn, bool bRedraw);
[System.Runtime.InteropServices.DllImport("user32")]
private static extern IntPtr GetDC(IntPtr hwnd);

复制代码 代码如下:
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);

IntPtr dc;
IntPtr region;

dc = GetDC(this.Handle);
BeginPath(dc);
SetBkMode(dc, TRANSPARENT);
Ellipse(dc, 0, 0, this.Width - 3, this.Height - 2);
EndPath(dc);
region = PathToRegion(dc);
SetWindowRgn(this.Handle, region, false);
}