winform 圆角窗体

Winform圆角窗体可以通过自定义类和继承实现。具体步骤如下：

1. 创建项目，添加自定义类：MyWin32.cs和PerPixelAlphaBlend.cs；圆角窗体RoundedForm ；继承RoundedForm的窗体Form1。

2. 在MyWin32.cs中添加以下代码：

using System;
using System.Runtime.InteropServices;

namespace Win32
{
    public static class MyWin32
    {
        [DllImport("user32.dll")]
        public static extern IntPtr GetDC(IntPtr hWnd);

        [DllImport("user32.dll")]
        public static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);

        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateCompatibleDC(IntPtr hDC);

        [DllImport("gdi32.dll")]
        public static extern int DeleteDC(IntPtr hDC);

        [DllImport("gdi32.dll")]
        public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);

        [DllImport("gdi32.dll")]
        public static extern int DeleteObject(IntPtr hObject);

        [DllImport("user32.dll")]
        public static extern int GetWindowRect(IntPtr hWnd, out RECT lpRect);

        [StructLayout(LayoutKind.Sequential)]
        public struct RECT
        {
            public int Left;
            public int Top;
            public int Right;
            public int Bottom;
        }
    }
}

3. 在PerPixelAlphaBlend.cs中添加以下代码：

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;

namespace Win32
{
    public static class PerPixelAlphaBlend
    {
        [DllImport("user32.dll")]
        public static extern IntPtr GetDC(IntPtr hWnd);

        [DllImport("user32.dll")]
        public static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);

        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateCompatibleDC(IntPtr hDC);

        [DllImport("gdi32.dll")]
        public static extern int DeleteDC(IntPtr hDC);

        [DllImport("gdi32.dll")]
        public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);

        [DllImport("gdi32.dll")]
        public static extern int DeleteObject(IntPtr hObject);

        [DllImport("msimg32.dll", EntryPoint = "AlphaBlend")]
        public static extern bool AlphaBlend(IntPtr hdcDest, int nXOriginDest, int nYOriginDest, int nWidthDest, int nHeightDest, IntPtr hdcSrc, int nXOriginSrc, int nYOriginSrc, int nWidthSrc, int nHeightSrc, BLENDFUNCTION blendFunction);

        [StructLayout(LayoutKind.Sequential)]
        public struct BLENDFUNCTION
        {
            public byte BlendOp;
            public byte BlendFlags;
            public byte SourceConstantAlpha;
            public byte AlphaFormat;
        }

        public static void SetBitmap(Bitmap bitmap, Control control)
        {
            SetBitmap(bitmap, control, 255);
        }

        public static void SetBitmap(Bitmap bitmap, Control control, byte opacity)
        {
            if (control == null)
            {
                throw new ArgumentNullException("control");
            }

            IntPtr screenDc = GetDC(IntPtr.Zero);
            IntPtr memDc = CreateCompatibleDC(screenDc);
            IntPtr hBitmap = IntPtr.Zero;
            IntPtr oldBitmap = IntPtr.Zero;

            try
            {
                hBitmap = bitmap.GetHbitmap(Color.FromArgb(0));
                oldBitmap = SelectObject(memDc, hBitmap);

                Size size = new Size(bitmap.Width, bitmap.Height);
                Point pointSource = new Point(0, 0);
                Point topPos = new Point(control.Left, control.Top);
                Win32.MyWin32.BLENDFUNCTION blend = new Win32.MyWin32.BLENDFUNCTION();
                blend.BlendOp = 0;
                blend.BlendFlags = 0;
                blend.SourceConstantAlpha = opacity;
                blend.AlphaFormat = 1;

                Win32.MyWin32.RECT sourceRect = new Win32.MyWin32.RECT()
                {
                    Left = pointSource.X,
                    Top = pointSource.Y,
                    Right = pointSource.X + size.Width,
                    Bottom = pointSource.Y + size.Height
                };

                Win32.MyWin32.RECT destRect = new Win32.MyWin32.RECT()
                {
                    Left = topPos.X,
                    Top = topPos.Y,
                    Right = topPos.X + size.Width,
                    Bottom = topPos.Y + size.Height
                };

                IntPtr screenDc2 = GetDC(IntPtr.Zero);
                AlphaBlend(screenDc2, destRect.Left, destRect.Top, destRect.Right - destRect.Left, destRect.Bottom - destRect.Top, memDc, sourceRect.Left, sourceRect.Top, sourceRect.Right - sourceRect.Left, sourceRect.Bottom - sourceRect.Top, blend);
                ReleaseDC(IntPtr.Zero, screenDc2);
            }
            finally
            {
                SelectObject(memDc, oldBitmap);
                DeleteObject(hBitmap);
                DeleteDC(memDc);
                ReleaseDC(IntPtr.Zero, screenDc);
            }
        }
    }
}

4. 在RoundedForm.cs中添加以下代码：

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;

namespace Win32
{
    public class RoundedForm : Form
    {
        private int radius = 20;

        public int Radius
        {
            get { return radius; }
            set { radius = value; }
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            GraphicsPath path = GetRoundPath(ClientRectangle, radius);

            this.Region = new Region(path);

            e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
            e.Graphics.FillPath(new SolidBrush(Color.White), path);
        }

        private GraphicsPath GetRoundPath(RectangleF rect, int radius)
        {
            float r2 = radius / 2f;
            GraphicsPath path = new GraphicsPath();
            path.AddArc(rect.X, rect.Y, radius, radius, 180, 90);
            path.AddLine(rect.X + r2, rect.Y, rect.Width - r2, rect.Y);
            path.AddArc(rect.X + rect.Width - radius, rect.Y, radius, radius, 270, 90);
            path.AddLine(rect.Width, rect.Y + r2, rect.Width, rect.Height - r2);
            path.AddArc(rect.X + rect.Width - radius, rect.Y + rect.Height - radius, radius, radius, 0, 90);
            path.AddLine(rect.Width - r2, rect.Height, rect.X + r2, rect.Height);
            path.AddArc(rect.X, rect.Y + rect.Height - radius, radius, radius, 90, 90);
            path.AddLine(rect.X, rect.Height - r2, rect.X, rect.Y + r2);
            path.CloseFigure();
            return path;
        }
    }
}

5. 在Form1.cs中继承RoundedForm，并添加以下代码：

public partial class Form1 : RoundedForm
{
    public Form1()
    {
        InitializeComponent();
        this.Radius = 20;
    }
}

6. 在Form1.Designer.cs中添加以下代码：

this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
this.ClientSize = new System.Drawing.Size(284, 261);
this.Name = "Form1";
this.Text = "Form1";

7. 在Form1_Load事件中添加以下代码：

private void Form1_Load(object sender, EventArgs e)
{
    this.BackColor = Color.FromArgb(0, 0, 0, 0);
    PerPixelAlphaBlend.SetBitmap(Properties.Resources.background, this);
}

其中，background是一个png格式的图片，用于设置窗体背景。