一、使用“用户控件”生成圆环进度条的dll

1、使用VS2019新建项目（类库）

2、添加用户控件

3 、用户控件PercentStar.cs源码编写

PercentStar.cs源码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace GDIPercent
{
    public partial class PercentStar : UserControl
    {
        public PercentStar()
        {
            InitializeComponent();
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);

            // 获取画布
            Graphics graphics = e.Graphics;

            //消除锯齿
            graphics.SmoothingMode = SmoothingMode.AntiAlias;
            //文字显示效果
            graphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.ClearTypeGridFit;
            //插补模式
            graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
            //图片呈现质量
            graphics.CompositingQuality = CompositingQuality.HighQuality;

            // 绘制底圆
            SolidBrush brush1 = new SolidBrush(Color.FromArgb(93, 107, 153));
            Rectangle rectangle1 = new Rectangle(1, 1, this.Width - 2, this.Height - 2);
            graphics.FillEllipse(brush1, rectangle1);

            //绘制扇形
            Rectangle rectangle2 = new Rectangle(1, 1, this.Width - 2, this.Height - 2);
            LinearGradientBrush brush2 = new LinearGradientBrush(rectangle2, Color.Blue, Color.Red, 150.0f, true);【绘制的圆环，随着进度条值增大，逐渐由蓝变为红色】
            //LinearGradientBrush brush2 = new LinearGradientBrush(rectangle2, Color.White, Color.Green, 150.0f, true);【绘制的圆环，随着进度条值增大，逐渐由白色变为绿色】
            this.PercentVal = (ActureValue / MaxValue) * 100;
            graphics.FillPie(brush2, rectangle2, -90, (ActureValue / MaxValue) * 360f);

            //绘制上圆
            SolidBrush solidBrushElipse = new SolidBrush(this.BackColor);
            Rectangle rectangle3 = new Rectangle(15, 15, this.Width - 30, this.Height - 30);
            graphics.FillEllipse(solidBrushElipse, rectangle3);

            //绘制文字
            Font font = new Font("华为宋体", 14);
            PointF point = new PointF(((float)this.Width) / 2.0f - 27, ((float)this.Height) / 2.0f - 10);
            graphics.DrawString(this.PercentVal.ToString("0.0") + "%", font, Brushes.Coral, point);
        }

        //最大值
        private float maxValue = 100;
        public float MaxValue
        {
            get { return maxValue; }
            set
            {
                maxValue = value;
                this.Invalidate();
            }
        }

        //实际值
        private float actureValue = 60;
        public float ActureValue
        {
            get { return actureValue; }
            set
            {
                actureValue = value;
                this.Invalidate();
            }
        }

        //文字显示值
        private float PercentVal = 0;

    }
}

二、引用dll，在Winform中代码实现

1、新建Windows窗体应用（.NET Framework）

2、添加引用（上边生成的GDIPercent.dll）

我一般放在当前项目的Debug文件夹下：

3、将dll添加到工具箱【两种方法】

方法一：鼠标选中GDIPercent.dll，直接拖放到工具栏【可以先添加个选项卡Myself,方便管理】

1、添加选项卡Myself

2、拖放GDIPercent.dll到Myself中

方法二：通过添加 .NET Framework组件 来添加

4、源码

using System;
using System.Windows.Forms;

namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            if (percentStar1.ActureValue == 100)
            {
                percentStar1.ActureValue = 0;
                return;
            }
            percentStar1.ActureValue += 1;
        }
    }
}

5、运行效果

6、补充【变换圆环进度条颜色】

当 一、3的代码改为下边时，显示如下的效果：

LinearGradientBrush brush2 = new LinearGradientBrush(rectangle2, Color.White, Color.Green, 150.0f, true);【绘制的圆环，随着进度条值增大，逐渐由白色变为绿色】