winform 自定义button如何变成圆角

要将Winform自定义按钮变成圆角，可以通过以下步骤操作：

创建一个自定义控件类，继承自Button类。
在该类的构造函数中，设置控件的样式为UserPaint，并启用双缓冲。

public class RoundButton : Button
{
    public RoundButton()
    {
        this.SetStyle(ControlStyles.UserPaint, true);
        this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
        this.SetStyle(ControlStyles.DoubleBuffer, true);
    }
}

重写OnPaint方法，在该方法中绘制圆角按钮的外观。

protected override void OnPaint(PaintEventArgs e)
{
    GraphicsPath path = new GraphicsPath();
    path.AddEllipse(new Rectangle(0, 0, this.Width, this.Height));
    this.Region = new Region(path);

    using (Brush brush = new SolidBrush(this.BackColor))
    {
        e.Graphics.FillEllipse(brush, new Rectangle(0, 0, this.Width, this.Height));
    }

    using (Pen pen = new Pen(this.ForeColor, 2))
    {
        e.Graphics.DrawEllipse(pen, new Rectangle(0, 0, this.Width, this.Height));
    }

    TextRenderer.DrawText(e.Graphics, this.Text, this.Font, new Rectangle(0, 0, this.Width, this.Height), this.ForeColor, TextFormatFlags.HorizontalCenter | TextFormatFlags.VerticalCenter);
}

在Winform窗体中使用该自定义按钮控件。

RoundButton roundButton1 = new RoundButton();
roundButton1.Text = "圆角按钮";
roundButton1.Size = new Size(100, 40);
this.Controls.Add(roundButton1);

通过以上步骤，可以将Winform自定义按钮控件变成圆角形状