C# 创建 圆角 button

要创建圆角 button，可以使用 C# 的 System.Windows.Forms 命名空间中的 Button 控件，并设置其 FlatStyle 属性为 FlatStyle.Flat，同时设置其 FlatAppearance 属性中的 BorderSize 和 CornerRadius 属性来实现圆角效果。

下面是一个示例代码：

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

public class RoundButton : Button
{
    public RoundButton()
    {
        this.FlatStyle = FlatStyle.Flat;
        this.FlatAppearance.BorderSize = 0;
        this.FlatAppearance.BorderColor = Color.FromArgb(0, 255, 255, 255);
        this.FlatAppearance.MouseDownBackColor = Color.FromArgb(255, 192, 192, 192);
        this.FlatAppearance.MouseOverBackColor = Color.FromArgb(255, 224, 224, 224);
        this.BackColor = Color.FromArgb(255, 255, 255, 255);
        this.Size = new Size(100, 50);
        this.CornerRadius = 10;
    }

    private int cornerRadius;
    public int CornerRadius
    {
        get { return cornerRadius; }
        set
        {
            cornerRadius = value;
            this.Invalidate();
        }
    }

    protected override void OnPaint(PaintEventArgs pevent)
    {
        base.OnPaint(pevent);
        Rectangle rectangle = new Rectangle(0, 0, this.Width - 1, this.Height - 1);
        GraphicsPath path = GetRoundedRectangle(rectangle, CornerRadius);
        this.Region = new Region(path);
        using (Pen pen = new Pen(this.FlatAppearance.BorderColor))
        {
            pevent.Graphics.DrawPath(pen, path);
        }
    }

    private GraphicsPath GetRoundedRectangle(Rectangle rectangle, int cornerRadius)
    {
        GraphicsPath path = new GraphicsPath();
        path.StartFigure();
        path.AddArc(rectangle.X, rectangle.Y, cornerRadius * 2, cornerRadius * 2, 180, 90);
        path.AddLine(rectangle.X + cornerRadius, rectangle.Y, rectangle.Right - cornerRadius * 2, rectangle.Y);
        path.AddArc(rectangle.X + rectangle.Width - cornerRadius * 2, rectangle.Y, cornerRadius * 2, cornerRadius * 2, 270, 90);
        path.AddLine(rectangle.Right, rectangle.Y + cornerRadius * 2, rectangle.Right, rectangle.Bottom - cornerRadius * 2);
        path.AddArc(rectangle.X + rectangle.Width - cornerRadius * 2, rectangle.Y + rectangle.Height - cornerRadius * 2, cornerRadius * 2, cornerRadius * 2, 0, 90);
        path.AddLine(rectangle.Right - cornerRadius * 2, rectangle.Bottom, rectangle.X + cornerRadius * 2, rectangle.Bottom);
        path.AddArc(rectangle.X, rectangle.Y + rectangle.Height - cornerRadius * 2, cornerRadius * 2, cornerRadius * 2, 90, 90);
        path.CloseFigure();
        return path;
    }
}

使用 RoundButton 控件时，可以像使用普通的 Button 控件一样进行操作，例如：

RoundButton roundButton = new RoundButton();
roundButton.Text = "Click Me";
this.Controls.Add(roundButton);

这样就可以创建一个带有圆角的 button 控件了。