检测 XML 的更好方法? [英] Better way to detect XML?

问题描述

目前，我有以下 c# 代码从文本中提取值.如果是 XML，我想要其中的值 - 否则，如果不是 XML，它可以只返回文本本身.

字符串数据 = "..."尝试{返回 XElement.Parse(data).Value;}捕捉(System.Xml.XmlException){返回数据；}

我知道异常在 C# 中很昂贵，所以我想知道是否有更好的方法来确定我正在处理的文本是否为 xml?

我想到了正则表达式测试，但我不认为这是一个更便宜的选择.请注意，我要求的是一种更便宜的方法.

解决方案

你可以对

做一个初步的检查.因为所有 XML 都必须以 1 开头，而所有非 XML 的大部分都不会以 1 开头.

(手写.)

//长度必须是 XMLif (!string.IsNullOrEmpty(data)){//如果它以 < 开头修剪后可能是XML//如果字符串全是空格，需要再次进行空检查.var trimmedData = data.TrimStart();if (string.IsNullOrEmpty(trimmedData)){返回数据；}if (trimmedData[0] == '<'){尝试{返回 XElement.Parse(data).Value;}捕捉(System.Xml.XmlException){返回数据；}}}别的{返回数据；}

我最初使用的是正则表达式，但 Trim()[0] 与该正则表达式的作用相同.

Currently, I have the following c# code to extract a value out of text. If its XML, I want the value within it - otherwise, if its not XML, it can just return the text itself.

String data = "..."
try
{
    return XElement.Parse(data).Value;
}
catch (System.Xml.XmlException)
{
    return data;
}

I know exceptions are expensive in C#, so I was wondering if there was a better way to determine if the text I'm dealing with is xml or not?

I thought of regex testing, but I dont' see that as a cheaper alternative. Note, I'm asking for a less expensive method of doing this.

解决方案

You could do a preliminary check for a < since all XML has to start with one and the bulk of all non-XML will not start with one.

(Free-hand written.)

// Has to have length to be XML
if (!string.IsNullOrEmpty(data))
{
    // If it starts with a < after trimming then it probably is XML
    // Need to do an empty check again in case the string is all white space.
    var trimmedData = data.TrimStart();
    if (string.IsNullOrEmpty(trimmedData))
    {
       return data;
    }

    if (trimmedData[0] == '<')
    {
        try
        {
            return XElement.Parse(data).Value;
        }
        catch (System.Xml.XmlException)
        {
            return data;
        }
    }
}
else
{
    return data;
}

I originally had the use of a regex but Trim()[0] is identical to what that regex would do.

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