写入然后从一个MemoryStream阅读 [英] Writing to then reading from a MemoryStream

问题描述

我使用DataContractJsonSerializer，它喜欢输出流。我想顶部和尾部串行器的输出，所以我使用的StreamWriter到我所需要的额外的比特交替书写。

I'm using DataContractJsonSerializer, which likes to output to a Stream. I want to top-and-tail the outputs of the serializer so I was using a StreamWriter to alternately write in the extra bits I needed.

var ser = new DataContractJsonSerializer(typeof (TValue));

using (var stream = new MemoryStream())
{   
    using (var sw = new StreamWriter(stream))
    {
        sw.Write("{");

        foreach (var kvp in keysAndValues)
        {
            sw.Write("'{0}':", kvp.Key);
            ser.WriteObject(stream, kvp.Value);
        }

        sw.Write("}");
    }

    using (var streamReader = new StreamReader(stream))
    {
        return streamReader.ReadToEnd();
    }
}

当我这样做，我得到一个ArgumentException流是无法读取。

When I do this I get an ArgumentException "Stream was not readable".

我可能做的种种错在这里让所有的答案欢迎。谢谢你。

I'm probably doing all sorts wrong here so all answers welcome. Thanks.

推荐答案

三件事情：

• 请不要关闭的StreamWriter 。这将关闭的MemoryStream 。你需要刷新，虽然作家。


• 阅读之前重置流的位置。


• 如果你要直接写入到流，你需要先刷新作家。

• Don't close the StreamWriter. That will close the MemoryStream. You do need to flush the writer though.
• Reset the position of the stream before reading.
• If you're going to write directly to the stream, you need to flush the writer first.

所以：

using (var stream = new MemoryStream())
{
    var sw = new StreamWriter(stream);
    sw.Write("{");

    foreach (var kvp in keysAndValues)
    {
        sw.Write("'{0}':", kvp.Key);
        sw.Flush();
        ser.WriteObject(stream, kvp.Value);
    }    
    sw.Write("}");            
    sw.Flush();
    stream.Position = 0;

    using (var streamReader = new StreamReader(stream))
    {
        return streamReader.ReadToEnd();
    }
}

还有一个更简单的选择虽然。所有你与阅读的将其转换为字符串时流做。你可以做到这一点更简单：

There's another simpler alternative though. All you're doing with the stream when reading is converting it into a string. You can do that more simply:

return Encoding.UTF8.GetString(stream.GetBuffer(), 0, stream.Length);

您可以做到这一点的之后的关闭流，因此，如果的StreamWriter 关闭它没关系。

You can do that after closing the stream, so it doesn't matter if the StreamWriter closes it.

我被你直接写入流而言 - 是什么辑？它是一个XML序列化，或者一个二进制？如果是二进制的，你的模型是有点瑕疵 - 你不应该不被非常小心它混合二进制和文本数据。如果是XML，你会发现，你在你的字符串的中间，这可能是有问题的结束与字节顺序标记。

I'm concerned by you writing directly to the the stream - what is ser? Is it an XML serializer, or a binary one? If it's binary, your model is somewhat flawed - you shouldn't mix binary and text data without being very careful about it. If it's XML, you may find that you end up with byte-order marks in the middle of your string, which could be problematic.

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