XmlException：文档元素未出现-行1，位置1 [英] XmlException: Document element did not appear - line 1, position 1

问题描述

我正试图反序列化xml字符串，但是由于某种原因，我得到了标题中指出的错误。

I'm tring to deserialize a xml string, but for some reason I'm getting the error stated in the title.

这是我要的代码反序列化自：

This is the code I'm deserializing from:

public void recieveObject<T>(ref T t){
        XmlSerializer xs = new XmlSerializer(typeof(T));
        Debug.Log("Waiting for client");
        byte[] recievedData = udpc.Receive(ref recieveFromEndPoint);

        if(recievedData.Length > 0){
            string xmlStr = System.Text.Encoding.UTF8.GetString(recievedData, 0, recievedData.Length);
            //xmlStr = xmlStr.Replace("\r","").Replace("\n", "").Replace("\t","").Replace(" ", "");
            Debug.Log(xmlStr);

            MemoryStream rms = new MemoryStream(1024);
            rms.Write (System.Text.Encoding.UTF8.GetBytes(xmlStr), 0, System.Text.Encoding.UTF8.GetBytes(xmlStr).Length);
            Debug.Log ("ms: " + System.Text.Encoding.UTF8.GetString(rms.ToArray()));
            t = (T) xs.Deserialize(rms);
        }
    }

从注释行可以看到，我什至尝试过

As you can see from the commented line I even tried stripping out the white space, but that didn't work eather.

这是我代码中对recieveObject函数的调用：

This is the call to the recieveObject function in my code:

recieveObject<Player>(ref player);

这是我的Player类：

And here is my Player class:

using UnityEngine;
using System.Collections;
using System.Xml.Serialization;

[XmlRoot("player")]
public class Player{
    [XmlElement("x")]
    public int x;

    [XmlElement("y")]
    public int y;

    [XmlElement("name")]
    public string name;

    private int maxNameLength = 12;

    public Player(){}
    public Player(int x, int y, string name){
        this.x = x;
        this.y = y;
        if(name.Length > maxNameLength) name = name.Substring(0, maxNameLength);
        this.name = name;
    }
}

最后是我尝试使用的Xml反序列化为播放器对象：

and finally the Xml I'm tryng to use to deserialize into a player object:

<player>
  <x>50</x>
  <y>100</y>
  <name>Tester</name>
</player>

有人可以告诉我为什么标题出现错误吗？

Can someone please tell me why I'm getting the error in the title?

谢谢您的时间。

推荐答案

您正在从内存流末读取：

You're reading from end of memory stream:

MemoryStream rms = new MemoryStream(1024);
rms.Write (...);

// Now cursor is at end of file, nothing to read here
t = (T) xs.Deserialize(rms);

在反序列化之前只需将光标移回开头：

Just move cursor back to beginning before you deserialize:

rms.Seek(0, SeekOrigin.Begin);
t = (T) xs.Deserialize(rms); // Now deserializer has data to read

的数据，最后只有两个小建议。不要忘记处理所有一次性对象：

Finally just two small suggestions. Don't forget to dispose all disposable objects:

MemoryStream rms = new MemoryStream(1024);
{
}

此外，您无需读取字节流成字符串（解码UTF8），然后又返回字节（来自UTF8），这种双重转换不会增加任何内容（此外，请注意两次编码，因为您两次调用 GetBytes（）） ：

Also you don't need to read a byte of stream into a string (decoding UTF8) then getting bytes back (from UTF8), this double conversion adds nothing (moreover please note you encode twice because you call GetBytes() twice):

if (recievedData.Length > 0) 
{
    using (MemoryStream rms = new MemoryStream(receivedData))
    {
       t = (T) xs.Deserialize(rms);
    }
}

出于记录目的，您可以编写如下函数（ UTF8转换将仅在必要时进行）：

For logging purposes you can write a function like this (UTF8 conversion will be done only if necessary):

static class Logger
{
    [Conditional("DEBUG")]
    public static void Debug(Func<string> text)
    {
        Debug.Log(text());
    }
}

您的日志记录将会（它将被称为仅在定义了 DEBUG 符号的情况下）：

Your logging will be (and it'll be called only if DEBUG symbol is defined):

Logger.Debug(() => "ms: " + Encoding.UTF8.GetString(rms.ToArray()));

这是一个更漂亮的选择：

It's just a more pretty alternative to:

#if DEBUG
    Debug.Log ("ms: " + System.Text.Encoding.UTF8.GetString(rms.ToArray()));
#endif

这篇关于XmlException：文档元素未出现-行1，位置1的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！