使用XmlTextWriter……

public static string PrintXML(string xml)
{
    string result = "";

    MemoryStream mStream = new MemoryStream();
    XmlTextWriter writer = new XmlTextWriter(mStream, Encoding.Unicode);
    XmlDocument document = new XmlDocument();

    try
    {
        // Load the XmlDocument with the XML.
        document.LoadXml(xml);

        writer.Formatting = Formatting.Indented;

        // Write the XML into a formatting XmlTextWriter
        document.WriteContentTo(writer);
        writer.Flush();
        mStream.Flush();

        // Have to rewind the MemoryStream in order to read
        // its contents.
        mStream.Position = 0;

        // Read MemoryStream contents into a StreamReader.
        StreamReader sReader = new StreamReader(mStream);

        // Extract the text from the StreamReader.
        string formattedXml = sReader.ReadToEnd();

        result = formattedXml;
    }
    catch (XmlException)
    {
        // Handle the exception
    }

    mStream.Close();
    writer.Close();

    return result;
}

可以使用XmlWriter通过流转换来漂亮地打印XML字符串。XmlReader WriteNode(真正的)。这个方法

将所有内容从读取器复制到写入器，并将读取器移动到下一个同级的开始。

定义以下扩展方法:

public static class XmlExtensions
{
    public static string FormatXml(this string xml, bool indent = true, bool newLineOnAttributes = false, string indentChars = "  ", ConformanceLevel conformanceLevel = ConformanceLevel.Document) => 
        xml.FormatXml( new XmlWriterSettings { Indent = indent, NewLineOnAttributes = newLineOnAttributes, IndentChars = indentChars, ConformanceLevel = conformanceLevel });

    public static string FormatXml(this string xml, XmlWriterSettings settings)
    {
        using (var textReader = new StringReader(xml))
        using (var xmlReader = XmlReader.Create(textReader, new XmlReaderSettings { ConformanceLevel = settings.ConformanceLevel } ))
        using (var textWriter = new StringWriter())
        {
            using (var xmlWriter = XmlWriter.Create(textWriter, settings))
                xmlWriter.WriteNode(xmlReader, true);
            return textWriter.ToString();
        }
    }
}

现在你可以做:

var inXml = @"<?xml version='1.0'?><response><error code='1'> Success</error></response>";
var newXml = inXml.FormatXml(indentChars : "", newLineOnAttributes : false); // Or true, if you prefer
Console.WriteLine(newXml);

的打印

<?xml version='1.0'?>
<response>
<error code="1"> Success</error>
</response>

注:

Other answers load the XML into some Document Object Model such as XmlDocument or XDocument/XElement, then re-serialize the DOM with indentation enabled. This streaming solution completely avoids the added memory overhead of a DOM. In your question you do not add any indentation for the nested <error code='1'> Success</error> node, so I set indentChars : "". Generally an indentation of two spaces per level of nesting is customary. Attribute delimiters will be unconditionally transformed to double-quotes if currently single-quotes. (I believe this is true of other answers as well.) Passing conformanceLevel : ConformanceLevel.Fragment allows strings containing sequences of XML fragments to be formatted. Other than ConformanceLevel.Fragment, the input XML string must be well-formed. If it is not, XmlReader will throw an exception.

这里是小样。

使用XmlTextWriter……

public static string PrintXML(string xml)
{
    string result = "";

    MemoryStream mStream = new MemoryStream();
    XmlTextWriter writer = new XmlTextWriter(mStream, Encoding.Unicode);
    XmlDocument document = new XmlDocument();

    try
    {
        // Load the XmlDocument with the XML.
        document.LoadXml(xml);

        writer.Formatting = Formatting.Indented;

        // Write the XML into a formatting XmlTextWriter
        document.WriteContentTo(writer);
        writer.Flush();
        mStream.Flush();

        // Have to rewind the MemoryStream in order to read
        // its contents.
        mStream.Position = 0;

        // Read MemoryStream contents into a StreamReader.
        StreamReader sReader = new StreamReader(mStream);

        // Extract the text from the StreamReader.
        string formattedXml = sReader.ReadToEnd();

        result = formattedXml;
    }
    catch (XmlException)
    {
        // Handle the exception
    }

    mStream.Close();
    writer.Close();

    return result;
}

如何漂亮地打印XML(不幸的是，该链接现在返回404:()

链接中的方法以XML字符串作为参数，并返回格式良好(缩进)的XML字符串。

我只是从链接中复制了示例代码，以使这个回答更全面和方便。

public static String PrettyPrint(String XML)
{
    String Result = "";

    MemoryStream MS = new MemoryStream();
    XmlTextWriter W = new XmlTextWriter(MS, Encoding.Unicode);
    XmlDocument D   = new XmlDocument();

    try
    {
        // Load the XmlDocument with the XML.
        D.LoadXml(XML);

        W.Formatting = Formatting.Indented;

        // Write the XML into a formatting XmlTextWriter
        D.WriteContentTo(W);
        W.Flush();
        MS.Flush();

        // Have to rewind the MemoryStream in order to read
        // its contents.
        MS.Position = 0;

        // Read MemoryStream contents into a StreamReader.
        StreamReader SR = new StreamReader(MS);

        // Extract the text from the StreamReader.
        String FormattedXML = SR.ReadToEnd();

        Result = FormattedXML;
    }
    catch (XmlException)
    {
    }

    MS.Close();
    W.Close();

    return Result;
}

对我来说，最简单的解决方法就是:

        XmlDocument xmlDoc = new XmlDocument();
        StringWriter sw = new StringWriter();
        xmlDoc.LoadXml(rawStringXML);
        xmlDoc.Save(sw);
        String formattedXml = sw.ToString();

如果你加载XMLDoc，我很确定. tostring()函数对此有重载。

但是这是用来调试的吗?这样发送的原因是为了占用更少的空间(即从XML中剥离不必要的空白)。