WeakReference v WeakReference<T>

WeakRef.cs

using System;
using System.Diagnostics;
using System.Xml;

namespace WeakReferenceDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            Debugger.Break();

            OldWay();
            NewWay();
            Console.ReadLine();
        }

        private static void OldWay()
        {
            var myWeaklyReferencedObject = BuildXmlDoc();
            var weakReference = new WeakReference(myWeaklyReferencedObject);

            XmlDocument myXmlDoc;

            // IsAlive method
            if (weakReference.IsAlive)
            {
                // cast to type
                myXmlDoc = (XmlDocument)weakReference.Target;
            }
            else
            {
                myXmlDoc = BuildXmlDoc();
                weakReference = new WeakReference(myXmlDoc);
            }

            Console.WriteLine(myXmlDoc.OuterXml);
        }

        private static void NewWay()
        {
            var myWeaklyReferencedObject = BuildXmlDoc();
            var weakReference = new WeakReference<XmlDocument>(myWeaklyReferencedObject);

            XmlDocument myXmlDoc;

            if (!weakReference.TryGetTarget(out myXmlDoc))
            {
                myXmlDoc = BuildXmlDoc();
                weakReference = new WeakReference<XmlDocument>(myXmlDoc);
            }

            Console.WriteLine(myXmlDoc.OuterXml);
        }

        private static XmlDocument BuildXmlDoc()
        {
            const string xml = @"<thing name='foo'><innerthing name='bar' /></thing>";
            var doc = new XmlDocument();
            doc.LoadXml(xml);
            return doc;
        }
    }
}