Serialize an object to string

I know this is not really an answer to the question, but based on the number of votes for the question and the accepted answer, I suspect the people are actually using the code to serialize an object to a string.

Using XML serialization adds unnecessary extra text rubbish to the output.

For the following class

public class UserData
{
    public int UserId { get; set; }
}

it generates

<?xml version="1.0" encoding="utf-16"?>
<UserData xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <UserId>0</UserId>
</UserData>

Better solution is to use JSON serialization (one of the best is Json.NET). To serialize an object:

var userData = new UserData {UserId = 0};
var userDataString = JsonConvert.SerializeObject(userData);

To deserialize an object:

var userData = JsonConvert.DeserializeObject<UserData>(userDataString);

The serialized JSON string would look like:

{"UserId":0}

Use a StringWriter instead of a StreamWriter:

public static string SerializeObject<T>(this T toSerialize)
{
    XmlSerializer xmlSerializer = new XmlSerializer(toSerialize.GetType());

    using(StringWriter textWriter = new StringWriter())
    {
        xmlSerializer.Serialize(textWriter, toSerialize);
        return textWriter.ToString();
    }
}

Note, it is important to use toSerialize.GetType() instead of typeof(T) in XmlSerializer constructor: if you use the first one the code covers all possible subclasses of T (which are valid for the method), while using the latter one will fail when passing a type derived from T.    Here is a link with some example code that motivate this statement, with XmlSerializer throwing an Exception when typeof(T) is used, because you pass an instance of a derived type to a method that calls SerializeObject that is defined in the derived type's base class: http://ideone.com/1Z5J1.

Also, Ideone uses Mono to execute code; the actual Exception you would get using the Microsoft .NET runtime has a different Message than the one shown on Ideone, but it fails just the same.

Serialize and Deserialize XML/JSON (SerializationHelper.cs):

using Newtonsoft.Json;
using System.IO;
using System.Xml.Serialization;

namespace MyProject.Helpers
{
    public static class SerializationHelper
    {
        public static T DeserializeXml<T>(this string toDeserialize)
        {
            XmlSerializer xmlSerializer = new XmlSerializer(typeof(T));
            using (StringReader textReader = new StringReader(toDeserialize))
            {
                return (T)xmlSerializer.Deserialize(textReader);
            }
        }

        public static string SerializeXml<T>(this T toSerialize)
        {
            XmlSerializer xmlSerializer = new XmlSerializer(typeof(T));
            using (StringWriter textWriter = new StringWriter())
            {
                xmlSerializer.Serialize(textWriter, toSerialize);
                return textWriter.ToString();
            }
        }

        public static T DeserializeJson<T>(this string toDeserialize)
        {
            return JsonConvert.DeserializeObject<T>(toDeserialize);
        }

        public static string SerializeJson<T>(this T toSerialize)
        {
            return JsonConvert.SerializeObject(toSerialize);
        }
    }
}