为什么使用 C# 创建 *.gz 文件后会得到损坏的文件？

Question

我正在开发一个 .NET 5、C# 控制台应用程序，用于从自定义对象列表创建一个 CSV 文件，对其进行 gzip 压缩，然后使用以下代码将其上传到 Azure 存储容器：

var blobServiceClient = new BlobServiceClient("My connection string");
var containerClient = GetBlobContainerClient("My container name");
var config = new CsvConfiguration(CultureInfo.CurrentCulture) { Delimiter = ";", Encoding = Encoding.UTF8 };

var list = new List<FakeModel>
{
   new FakeModel { Field1 = "A", Field2 = "B" },
   new FakeModel { Field1 = "C", Field2 = "D" }
};

await using var memoryStream = new MemoryStream();
await using var streamWriter = new StreamWriter(memoryStream);
await using var csvWriter = new CsvWriter(streamWriter, config);

await csvWriter.WriteRecordsAsync(list);

await using var zip = new GZipStream(memoryStream, CompressionMode.Compress, true);
await memoryStream.CopyToAsync(zip);

memoryStream.Seek(0, SeekOrigin.Begin);
var blockBlob = containerClient.GetBlockBlobClient("test.csv.gz");
await blockBlob.UploadAsync(memoryStream);

它似乎可以工作，但是当我从云端下载 gzip 进行检查时，尝试解压缩时出现以下错误：

检查文件显示它的长度为 0。

你能帮我理解为什么吗？

Answer 1

new GZipStream 的流参数是 destination 流。要处理输入到输出，您需要以某种方式写入 GZipStream 的实例。

当我尝试使用它时，我发现需要调用csvWriter.FlushAsync()。

像这样：

class Program
{
    public class FakeModel
    {
        public string Field1 { get; set; }
        public string Field2 { get; set; }
    }

    static async Task Main(string[] args)
    {
        var config = new CsvConfiguration(CultureInfo.CurrentCulture) { Delimiter = ";", Encoding = Encoding.UTF8 };

        var list = new List<FakeModel>
                        {
                           new FakeModel { Field1 = "A", Field2 = "B" },
                           new FakeModel { Field1 = "C", Field2 = "D" }
                        };

        await using var memoryStream = new MemoryStream();
        await using var streamWriter = new StreamWriter(memoryStream);
        await using var csvWriter = new CsvWriter(streamWriter, config);

        await csvWriter.WriteRecordsAsync(list);
        await csvWriter.FlushAsync();

        memoryStream.Position = 0;

        await using var fs = new FileStream(@"C:\temp\SO67935249.csv.gz", FileMode.Create);
        await using var zip = new GZipStream(fs, CompressionMode.Compress, true);
        await memoryStream.CopyToAsync(zip);

    }
}