自定义进度条码：

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

namespace Download_Videos
{
    public enum ProgressBarDisplayText
    {
        Percentage,
        CustomText
    }

    public partial class ProgressBarText : ProgressBar
    {
        //Property to set to decide whether to print a % or Text
        public ProgressBarDisplayText DisplayStyle { get; set; }

        //Property to hold the custom text
        public String CustomText { get; set; }

        public ProgressBarText()
        {
            // Modify the ControlStyles flags
            //http://msdn.microsoft.com/en-us/library/system.windows.forms.controlstyles.aspx
            SetStyle(ControlStyles.UserPaint | ControlStyles.AllPaintingInWmPaint | ControlStyles.OptimizedDoubleBuffer, true);
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            Rectangle rect = ClientRectangle;
            Graphics g = e.Graphics;

            ProgressBarRenderer.DrawHorizontalBar(g, rect);
            rect.Inflate(-3, -3);
            if (Value > 0)
            {
                // As we doing this ourselves we need to draw the chunks on the progress bar
                Rectangle clip = new Rectangle(rect.X, rect.Y, (int)Math.Round(((float)Value / Maximum) * rect.Width), rect.Height);
                ProgressBarRenderer.DrawHorizontalChunks(g, clip);
            }

            // Set the Display text (Either a % amount or our custom text
            int percent = (int)(((double)this.Value / (double)this.Maximum) * 100);
            string text = DisplayStyle == ProgressBarDisplayText.Percentage ? percent.ToString() + '%' : CustomText;

            using (Font f = new Font(FontFamily.GenericSerif, 10))
            {

                SizeF len = g.MeasureString(text, f);
                // Calculate the location of the text (the middle of progress bar)
                // Point location = new Point(Convert.ToInt32((rect.Width / 2) - (len.Width / 2)), Convert.ToInt32((rect.Height / 2) - (len.Height / 2)));
                Point location = new Point(Convert.ToInt32((Width / 2) - len.Width / 2), Convert.ToInt32((Height / 2) - len.Height / 2));
                // The commented-out code will centre the text into the highlighted area only. This will centre the text regardless of the highlighted area.
                // Draw the custom text
                g.DrawString(text, f, Brushes.Red, location);
            }
        }
    }
}

它显示百分比很好，但当我将其更改为在构造函数中显示文本时：

public Form1()
        {
            InitializeComponent();

            progressBarText1.DisplayStyle = ProgressBarDisplayText.CustomText;
        }

然后设置文本：

private void ProgressChanged(object sender, DownloadProgressChangedEventArgs e, Stopwatch sw)
        {
            string downloadProgress = e.ProgressPercentage + "%";
            string downloadSpeed = string.Format("{0} MB/s", (e.BytesReceived / 1024.0 / 1024.0 / sw.Elapsed.TotalSeconds).ToString("0.00"));
            string downloadedMBs = Math.Round(e.BytesReceived / 1024.0 / 1024.0) + " MB";
            string totalMBs = Math.Round(e.TotalBytesToReceive / 1024.0 / 1024.0) + " MB";

            string progress = $"{downloadedMBs}/{totalMBs} ({downloadProgress}) @ {downloadSpeed}";

            label1.Text = progress;
            progressBarText1.CustomText = progress;
        }

progressBar为空，progressBar上没有显示任何内容。当我使用：

progressBarText1.Value = e.ProgressPercentage;

它在progressBar的中心显示百分比，但是显示文本不起作用，它什么都不显示.