带有进度条的 C# 异步文件复制

Question

我正在尝试编写一个 C# 应用程序，在复制多个文件时更新进度条。我正在使用这种方法进行复制，需要 Dictionary<string, string>:

public static async Task CopyFiles(Dictionary<string, string> files, IProgress<int> progressCallback)
{
    for (var x = 0; x < files.Count; x++)
    {
        var item = files.ElementAt(x);
        var from = item.Key;
        var to = item.Value;

        using (var outStream = new FileStream(to, FileMode.Create, FileAccess.Write, FileShare.Read))
        {
            using (var inStream = new FileStream(from, FileMode.Open, FileAccess.Read, FileShare.Read))
            {
                await inStream.CopyToAsync(outStream);
            }
        }

        var percentComplete = ((x + 1) / files.Count) * 100;
        //progressCallback((int)((x + 1) / files.Count) * 100);
        progressCallback.Report(percentComplete);
    }
}

在我的主类中，我正在使用以下代码尝试更新我的进度条 (progressBar1)，但此代码似乎无法正常工作，似乎在复制两个文件和结束时完成了 ProgressBar大约需要一秒钟才能完成，不知道为什么会这样。

private async void button4_Click(object sender, EventArgs e) 
{
        button4.Enabled = false;

        var progress = new Progress<int>(percent =>
        {
            progressBar1.Value = percent;
        });

        await Copier.CopyFiles(new Dictionary<string, string> {
            { Source1, Destination1 },
            { Source2, Destination2 }
        },
            progress);

        button4.Enabled = true;
        MessageBox.Show("Completed");
    }
}

Answer 1

问题是因为整数除法x + 1 / files.Count 为除最后一个之外的每个x 返回零。您可以通过先乘以 100 (100*(x+1)/files.Count) 来解决此问题，但还有更好的选择。

无需在CopyFiles 中计算和报告百分比。您可以设置进度条的最大值：

    private async void button4_Click(object sender, EventArgs e) 
    {
            button4.Enabled = false;

            var files = new Dictionary<string, string> {
                { Source1, Destination1 },
                { Source2, Destination2 }
            };
            
            progressBar1.Maximum=files.Count;
            progressBar1.Value =0;
            var progress = new Progress<int>(x =>
            {
                progressBar1.Value = x+1;
            });

            await Copier.CopyFiles(files,progress);

            button4.Enabled = true;
            MessageBox.Show("Completed");
        }
    }

并且只报告当前的迭代：

    public static async Task CopyFiles(Dictionary<string, string> files, IProgress<int> progressCallback)
    {
        for (var x = 0; x < files.Count; x++)
        {
            
            ...
            progressCallback.Report(x);
        }
    }

IProgress< T> 可以处理复杂的对象，而不仅仅是原始类型。可以报​​告迭代和文件名以显示在状态栏中：

record CopyProgress(int Iteration, string From, string To);
...

var progress = new Progress<int>(x =>
        {
            progressBar1.Value = x.Iteration;
            statusText.Text = $"Copied {x.From} to {x.To}";
        });

...
progressCallback.Report(new CopyProgress(x,from,to);