从XmlDocument用换行符缩进XML的最简单方法是什么？

当我从头开始构建XML时 XmlDocument，该OuterXml属性已经包含了所有带有换行符的缩进。但是，如果我调用LoadXml一些非常“压缩”的XML（没有换行或缩进），则OuterXml保持输出。所以...

从的实例获取美化的XML输出的最简单方法是什么 XmlDocument什么？

根据其他答案，我研究XmlTextWriter并提出了以下帮助方法：

static public string Beautify(this XmlDocument doc)
{
    StringBuilder sb = new StringBuilder();
    XmlWriterSettings settings = new XmlWriterSettings
    {
        Indent = true,
        IndentChars = "  ",
        NewLineChars = "\r\n",
        NewLineHandling = NewLineHandling.Replace
    };
    using (XmlWriter writer = XmlWriter.Create(sb, settings)) {
        doc.Save(writer);
    }
    return sb.ToString();
}

它的代码比我期望的要多，但它的工作方式只是桃花心木。

根据Erika Ehrli的博客改编而成，应该这样做：

XmlDocument doc = new XmlDocument();
doc.LoadXml("<item><name>wrench</name></item>");
// Save the document to a file and auto-indent the output.
using (XmlTextWriter writer = new XmlTextWriter("data.xml", null)) {
    writer.Formatting = Formatting.Indented;
    doc.Save(writer);
}

甚至可以轻松访问Linq

try
{
    RequestPane.Text = System.Xml.Linq.XElement.Parse(RequestPane.Text).ToString();
}
catch (System.Xml.XmlException xex)
{
            displayException("Problem with formating text in Request Pane: ", xex);
}

较短的扩展方法版本

public static string ToIndentedString( this XmlDocument doc )
{
    var stringWriter = new StringWriter(new StringBuilder());
    var xmlTextWriter = new XmlTextWriter(stringWriter) {Formatting = Formatting.Indented};
    doc.Save( xmlTextWriter );
    return stringWriter.ToString();
}

如果正在针对XmlDocument已经包含XmlProcessingInstruction子节点的调用上述Beautify方法，则会引发以下异常：

无法编写XML声明。WriteStartDocument方法已经编写了它。

这是我对原始版本的修改后的版本，以消除该异常：

private static string beautify(
    XmlDocument doc)
{
    var sb = new StringBuilder();
    var settings =
        new XmlWriterSettings
            {
                Indent = true,
                IndentChars = @"    ",
                NewLineChars = Environment.NewLine,
                NewLineHandling = NewLineHandling.Replace,
            };

    using (var writer = XmlWriter.Create(sb, settings))
    {
        if (doc.ChildNodes[0] is XmlProcessingInstruction)
        {
            doc.RemoveChild(doc.ChildNodes[0]);
        }

        doc.Save(writer);
        return sb.ToString();
    }
}

现在它对我有效，可能您需要扫描该XmlProcessingInstruction节点的所有子节点，而不仅仅是第一个节点？

2015年4月更新：

由于还有另一种编码错误的情况，因此我搜索了如何在没有BOM的情况下强制执行UTF-8。我找到了此博客文章，并基于它创建了一个函数：

private static string beautify(string xml)
{
    var doc = new XmlDocument();
    doc.LoadXml(xml);

    var settings = new XmlWriterSettings
    {
        Indent = true,
        IndentChars = "\t",
        NewLineChars = Environment.NewLine,
        NewLineHandling = NewLineHandling.Replace,
        Encoding = new UTF8Encoding(false)
    };

    using (var ms = new MemoryStream())
    using (var writer = XmlWriter.Create(ms, settings))
    {
        doc.Save(writer);
        var xmlString = Encoding.UTF8.GetString(ms.ToArray());
        return xmlString;
    }
}

XmlTextWriter xw = new XmlTextWriter(writer);
xw.Formatting = Formatting.Indented;

    public static string FormatXml(string xml)
    {
        try
        {
            var doc = XDocument.Parse(xml);
            return doc.ToString();
        }
        catch (Exception)
        {
            return xml;
        }
    }

一种简单的方法是使用：

writer.WriteRaw(space_char);

像此示例代码一样，此代码是我用来使用XMLWriter创建类似于结构的树形视图的代码：

private void generateXML(string filename)
        {
            using (XmlWriter writer = XmlWriter.Create(filename))
            {
                writer.WriteStartDocument();
                //new line
                writer.WriteRaw("\n");
                writer.WriteStartElement("treeitems");
                //new line
                writer.WriteRaw("\n");
                foreach (RootItem root in roots)
                {
                    //indent
                    writer.WriteRaw("\t");
                    writer.WriteStartElement("treeitem");
                    writer.WriteAttributeString("name", root.name);
                    writer.WriteAttributeString("uri", root.uri);
                    writer.WriteAttributeString("fontsize", root.fontsize);
                    writer.WriteAttributeString("icon", root.icon);
                    if (root.children.Count != 0)
                    {
                        foreach (ChildItem child in children)
                        {
                            //indent
                            writer.WriteRaw("\t");
                            writer.WriteStartElement("treeitem");
                            writer.WriteAttributeString("name", child.name);
                            writer.WriteAttributeString("uri", child.uri);
                            writer.WriteAttributeString("fontsize", child.fontsize);
                            writer.WriteAttributeString("icon", child.icon);
                            writer.WriteEndElement();
                            //new line
                            writer.WriteRaw("\n");
                        }
                    }
                    writer.WriteEndElement();
                    //new line
                    writer.WriteRaw("\n");
                }

                writer.WriteEndElement();
                writer.WriteEndDocument();

            }

        }

这样，您可以按照通常的方式添加制表符或换行符，即\ t或\ n

在实施此处发布的建议时，我在文本编码方面遇到了麻烦。似乎的编码已XmlWriterSettings被忽略，并且始终被流的编码所覆盖。当使用StringBuilder，这始终是C＃内部使用的文本编码，即UTF-16。

所以这是一个也支持其他编码的版本。

重要说明：如果您的XMLDocument对象具有其格式，则格式将被完全忽略preserveWhitespace在加载文档时属性已启用，。这让我难过了一段时间，所以请确保不要启用它。

我的最终代码：

public static void SaveFormattedXml(XmlDocument doc, String outputPath, Encoding encoding)
{
    XmlWriterSettings settings = new XmlWriterSettings();
    settings.Indent = true;
    settings.IndentChars = "\t";
    settings.NewLineChars = "\r\n";
    settings.NewLineHandling = NewLineHandling.Replace;

    using (MemoryStream memstream = new MemoryStream())
    using (StreamWriter sr = new StreamWriter(memstream, encoding))
    using (XmlWriter writer = XmlWriter.Create(sr, settings))
    using (FileStream fileWriter = new FileStream(outputPath, FileMode.Create))
    {
        if (doc.ChildNodes.Count > 0 && doc.ChildNodes[0] is XmlProcessingInstruction)
            doc.RemoveChild(doc.ChildNodes[0]);
        // save xml to XmlWriter made on encoding-specified text writer
        doc.Save(writer);
        // Flush the streams (not sure if this is really needed for pure mem operations)
        writer.Flush();
        // Write the underlying stream of the XmlWriter to file.
        fileWriter.Write(memstream.GetBuffer(), 0, (Int32)memstream.Length);
    }
}

这将使用给定的文本编码将格式化的xml保存到磁盘。

如果您有XML字符串，而不是可以使用的文档，则可以通过以下方式实现：

var xmlString = "<xml>...</xml>"; // Your original XML string that needs indenting.
xmlString = this.PrettifyXml(xmlString);

private string PrettifyXml(string xmlString)
{
    var prettyXmlString = new StringBuilder();

    var xmlDoc = new XmlDocument();
    xmlDoc.LoadXml(xmlString);

    var xmlSettings = new XmlWriterSettings()
    {
        Indent = true,
        IndentChars = " ",
        NewLineChars = "\r\n",
        NewLineHandling = NewLineHandling.Replace
    };

    using (XmlWriter writer = XmlWriter.Create(prettyXmlString, xmlSettings))
    {
        xmlDoc.Save(writer);
    }

    return prettyXmlString.ToString();
}

基于公认答案的更简化方法：

static public string Beautify(this XmlDocument doc) {
    StringBuilder sb = new StringBuilder();
    XmlWriterSettings settings = new XmlWriterSettings
    {
        Indent = true
    };

    using (XmlWriter writer = XmlWriter.Create(sb, settings)) {
        doc.Save(writer);
    }

    return sb.ToString(); 
}

无需设置新行。缩进字符也具有默认的两个空格，因此我也不想设置它。