现在可能太晚了，但是只有用户定义的命名空间是序列化的:

public static string XmlSerialize<T>(this T obj) where T : class
        {
            Type serialType = typeof(T);
            var xsSubmit = new XmlSerializer(serialType);

            XmlWriterSettings xws = new XmlWriterSettings() { OmitXmlDeclaration = true, Indent = true };
            

            var Namespaces = new XmlSerializerNamespaces(new XmlQualifiedName[] {           
            new XmlQualifiedName(string.Empty,  GetXmlNameSpace(serialType) ?? string.Empty )


        });
 private static string GetXmlNameSpace(Type target)
        {
            XmlRootAttribute attribute = (XmlRootAttribute)Attribute.GetCustomAttribute(target, typeof(XmlRootAttribute));
            return attribute == null ? null : attribute.Namespace;
        }

并在自定义类中定义命名空间

 [XmlRoot("IdentityTerminal",Namespace = "http://my-name-space/XMLSchema")]
   
    public class IdentityTerminal
    {
    }

这段代码允许只使用用户定义的名称空间，而忽略默认的名称空间。

要序列化一个对象，请执行:

 using (StreamWriter myWriter = new StreamWriter(path, false))
 {
     XmlSerializer mySerializer = new XmlSerializer(typeof(your_object_type));
     mySerializer.Serialize(myWriter, objectToSerialize);
 }

还要记住，要使XmlSerializer工作，需要一个无参数构造函数。

以上所有点赞的答案都是正确的。这是最简单的版本:

private string Serialize(Object o)
{
    using (var writer = new StringWriter())
    {
        new XmlSerializer(o.GetType()).Serialize(writer, o);
        return writer.ToString();
    }
}

扩展类:

using System.IO;
using System.Xml;
using System.Xml.Serialization;

namespace MyProj.Extensions
{
    public static class XmlExtension
    {
        public static string Serialize<T>(this T value)
        {
            if (value == null) return string.Empty;

            var xmlSerializer = new XmlSerializer(typeof(T));

            using (var stringWriter = new StringWriter())
            {
                using (var xmlWriter = XmlWriter.Create(stringWriter,new XmlWriterSettings{Indent = true}))
                {
                    xmlSerializer.Serialize(xmlWriter, value);
                    return stringWriter.ToString();
                }    
            }
        }
    }
}

用法:

Foo foo = new Foo{MyProperty="I have been serialized"};

string xml = foo.Serialize();

只是引用名称空间持有您的扩展方法在文件中，你想使用它，它将工作(在我的例子中，它将是:使用myproject . extensions;)

请注意，如果您想使扩展方法只特定于一个特定的类(例如。， Foo)，你可以在扩展方法中替换T参数。

序列化(这个Foo值){…}

这比调用类的ToString方法要复杂一些，但也不是很复杂。

下面是一个简单的下拉函数，可以用来序列化任何类型的对象。它返回一个包含序列化XML内容的字符串:

public string SerializeObject(object obj)
{
    System.Xml.XmlDocument xmlDoc = new System.Xml.XmlDocument();
    System.Xml.Serialization.XmlSerializer serializer = new System.Xml.Serialization.XmlSerializer(obj.GetType());
    using (System.IO.MemoryStream ms = new System.IO.MemoryStream()) {
        serializer.Serialize(ms, obj);
        ms.Position = 0;
        xmlDoc.Load(ms);
        return xmlDoc.InnerXml;
    }
}

必须使用XmlSerializer进行XML序列化。下面是一个示例代码片段。

 XmlSerializer xsSubmit = new XmlSerializer(typeof(MyObject));
 var subReq = new MyObject();
 var xml = "";

 using(var sww = new StringWriter())
 {
     using(XmlWriter writer = XmlWriter.Create(sww))
     {
         xsSubmit.Serialize(writer, subReq);
         xml = sww.ToString(); // Your XML
     }
 }

根据泛型类的@kiquenet请求:

public class MySerializer<T> where T : class
{
    public static string Serialize(T obj)
    {
        XmlSerializer xsSubmit = new XmlSerializer(typeof(T));
        using (var sww = new StringWriter())
        {
            using (XmlTextWriter writer = new XmlTextWriter(sww) { Formatting = Formatting.Indented })
            {
                xsSubmit.Serialize(writer, obj);
                return sww.ToString();
            }
        }
    }
}

用法:

string xmlMessage = MySerializer<MyClass>.Serialize(myObj);