因为你要在整个XML文档中替换它我会去找这个简单易读的方法：

Since you're replacing it in the entire XML document I'd go for this simple and readable approach:

using System.Xml;
using System.Text.RegularExpressions;

public static class XMLExtensions
{
    public static void RemoveNamespace(this XmlDocument document, string @namespace) =>
        document.InnerXml = Regex.Replace(
            document.InnerXml,

@ （？< = \< / | \<）{@ namespace}：，
）;
}

@"(?<=\</|\<){@namespace}:", ""); }

编辑：如果某些数据被命名为APCS，则更改正则表达式以仅捕获标记中的名称空间。非贪婪默认设置的小修复。



EDIT2：xmlns命名空间通常只包含一次，但如果你需要以编程方式删除它，这将是这样做：

Changed regex to catch only namespaces in tags in case some data is named APCS. Small fix in case of a non-greedy default setting.

The xmlns namespace is usually only included once but if you need to programmatically remove it as well this will do it:

using System.Xml;
using System.Text.RegularExpressions;

public static class XMLExtensions
{
    public static void RemoveNamespace(this XmlDocument document, string @namespace) =>
        document.InnerXml = Regex.Replace(
            document.InnerXml,

@ （（？< = \< / | \<）{@ namespace}：| xmlns：{@ namespace} = [^] +），
）;
}

@"((?<=\</|\<){@namespace}:|xmlns:{@namespace}=""[^""]+"")", ""); }