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Sanvirtus
Asked:2020-07-26 19:38:56 +0000 UTC2020-07-26 19:38:56 +0000 UTC

如何将 FileStream 转换为 Stream？

  • 772

我打开文件并将其读入流中，现在当我调用该方法时，我需要进一步传输该流，但出现错误 Stream != FileStream. 如何正确地将 FileStream 转换为 Stream 并将其传递给执行？

using (var fileStream = File.Open(file, FileMode.Open))
{
    var buffer = new byte[fileStream.Length];
    fileStream.Read(buffer, 0, buffer.Length);

    await _conversationsRepository.Attachment(new Attachment
    {
        Name = Path.GetFileName(file),
        Stream = fileStream
    });
}

public bool Attachment(Attachment attachment)
{
    if (attachment.Stream == null)
    {
        return false;
    }

    if (string.IsNullOrWhiteSpace(attachment.Name))
    {
        return false;
    }

    if (attachment.Stream.Length > 30 * 1024 * 1024)
    {
        return false;
    }
    console.log("true");
    return true;
}

这是课程本身：

using System;
using System.IO;

namespace Models
{
    public class Attachment
    {
        public Stream Stream { get; set; }

        public string Name { get; set; }

        public AttachmentType Type { get; set; }
    }
}

如果我这样做了，那么流仍然是空的。

var stream = Stream.Null;
fileStream.CopyTo(stream);

var stream2 = new MemoryStream();
fileStream.CopyTo(stream2);
c#

3 个回答

  1. Best Answer

    问题通过以下方式解决：

    using (var fileStream = File.Open(file, FileMode.Open))
{
    var buffer = new byte[fileStream.Length];
    fileStream.Read(buffer, 0, buffer.Length);

    await _conversationsRepository.Attachment(new Attachment
    {
        Name = Path.GetFileName(file),
    }, buffer);
}

public bool Attachment(Attachment attachment, byte[] buffer)
{
    Attachment.Stream = new MemoryStream(buffer);
    if (attachment.Stream == null)
    {
        return false;
    }

    if (string.IsNullOrWhiteSpace(attachment.Name))
    {
        return false;
    }

    if (attachment.Stream.Length > 30 * 1024 * 1024)
    {
        return false;
    }
    console.log("true");
    return true;
}
    • 0

  2. Stream 是 FileStream 类的祖先，也就是说，您可以简单地进行向上转换。

    FileStream filestream = ...
Stream b = filestream;

    UPD：试试这个：替换

    using (var fileStream = File.Open(file, FileMode.Open))
   {
    var buffer = new byte[fileStream.Length];
    fileStream.Read(buffer, 0, buffer.Length);

    await _conversationsRepository.Attachment(new Attachment
    {
        Name = Path.GetFileName(file),
        Stream = fileStream
    });
    }

    在

     await _conversationsRepository.Attachment(new Attachment
 {
    Name = Path.GetFileName(file),
    Stream = File.Open(file, FileMode.Open)
 });
    • -1

  3. 创建一个内存流。

    using (var fileStream = File.Open(file, FileMode.Open))
{
   MemoryStream stream = new MemoryStream();
   fileStream.CopyTo(stream)

   await _conversationsRepository.Attachment(new Attachment
   {
      Name = Path.GetFileName(file),
      Stream = stream
   });
}

    只要您的文件大小满足以下条件，这应该可以工作：> 30 * 1024 * 1024。

    UPD：我想通了，最好直接把文件流传到附件里。

    var fileStream = File.Open(file, FileMode.Open);

await _conversationsRepository.Attachment(new Attachment
{
    Name = Path.GetFileName(file),
    Stream = fileStream;
 });

    由于在内存中存储 30MB 是昂贵的。

    • -1

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