我修改了我的返回一个字符串，而不是像下面这样使用一个ref变量。

public static string Serialize<T>(this T value)
{
    if (value == null)
    {
        return string.Empty;
    }
    try
    {
        var xmlserializer = new XmlSerializer(typeof(T));
        var stringWriter = new StringWriter();
        using (var writer = XmlWriter.Create(stringWriter))
        {
            xmlserializer.Serialize(writer, value);
            return stringWriter.ToString();
        }
    }
    catch (Exception ex)
    {
        throw new Exception("An error occurred", ex);
    }
}

它的用法是这样的:

var xmlString = obj.Serialize();

我的工作代码。返回utf8 xml启用空命名空间。

// override StringWriter
public class Utf8StringWriter : StringWriter
{
    public override Encoding Encoding => Encoding.UTF8;
}

private string GenerateXmlResponse(Object obj)
{    
    Type t = obj.GetType();

    var xml = "";

    using (StringWriter sww = new Utf8StringWriter())
    {
        using (XmlWriter writer = XmlWriter.Create(sww))
        {
            var ns = new XmlSerializerNamespaces();
            // add empty namespace
            ns.Add("", "");
            XmlSerializer xsSubmit = new XmlSerializer(t);
            xsSubmit.Serialize(writer, obj, ns);
            xml = sww.ToString(); // Your XML
        }
    }
    return xml;
}

示例返回响应Yandex api支付Aviso url:

<?xml version="1.0" encoding="utf-8"?><paymentAvisoResponse xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" performedDatetime="2017-09-01T16:22:08.9747654+07:00" code="0" shopId="54321" invoiceId="12345" orderSumAmount="10643" />

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();
    }
}

我修改了我的返回一个字符串，而不是像下面这样使用一个ref变量。

public static string Serialize<T>(this T value)
{
    if (value == null)
    {
        return string.Empty;
    }
    try
    {
        var xmlserializer = new XmlSerializer(typeof(T));
        var stringWriter = new StringWriter();
        using (var writer = XmlWriter.Create(stringWriter))
        {
            xmlserializer.Serialize(writer, value);
            return stringWriter.ToString();
        }
    }
    catch (Exception ex)
    {
        throw new Exception("An error occurred", ex);
    }
}

它的用法是这样的:

var xmlString = obj.Serialize();

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。

基于上述解决方案，这里有一个扩展类，您可以使用它序列化和反序列化任何对象。任何其他XML属性都由您决定。

就像这样使用它:

        string s = new MyObject().Serialize(); // to serialize into a string
        MyObject b = s.Deserialize<MyObject>();// deserialize from a string



internal static class Extensions
{
    public static T Deserialize<T>(this string value)
    {
        var xmlSerializer = new XmlSerializer(typeof(T));

        return (T)xmlSerializer.Deserialize(new StringReader(value));
    }

    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();
            }
        }
    }
}