Downloads: Dynamic/Transparent Proxy using DynamicProxy.NET

dynamicproxy.zip

DynamicProxy

AssemblyInfo.cs

bin

Release

DynamicProxy.dll

docs

dynamicproxy.htm

tutorial.png

tutorial2.png

DynamicProxy.csproj

DynamicProxy.csproj.user

DynamicProxyFactory.cs

DynamicProxyImpl.cs

IDynamicProxy.cs

license.txt

DynamicProxyTest

App.ico

AssemblyInfo.cs

bin

Release

DynamicProxy.dll

DynamicProxyTest.exe

ConsoleTest.cs

DynamicProxyTest.csproj

DynamicProxyTest.csproj.user

license.txt

TestClasses

IImplemented.cs

INotImplemented.cs

INotImplemented2.cs

ISimpleInterface.cs

SimpleClass.cs

UnitTest.cs

dynamicproxytutorial.zip

DynamicProxyTutorial

App.ico

AssemblyInfo.cs

bin

Release

DynamicProxy.dll

DynamicProxyTutorial.exe

DynamicFileViewerProxy.cs

DynamicProxyTutorial.csproj

DynamicProxyTutorial.csproj.user

FileViewer.cs

FileViewerProxy.cs

FileViewerProxyFactory.cs

IFileViewer.cs

MainForm.cs

MainForm.resx

Performance.cs

SecurityException.cs

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
	<head>
		<title>DynamicProxy for .NET</title>
		<style> body { font-family: verdana, arial; font-size: 10pt; }
	</style>
	</head>
	<body>
		<h1>DynamicProxy.NET</h1>
		<P>Last updated the 17. of October 2003</P>
		<p>.NET doesn't come with a ready to use Dynamic proxy in the same sense that Java 
			does.<br>
			However, there is some Proxy support in .NET, through the Remoting feature, 
			namely the RealProxy class.
		</p>
		<p>DynamicProxy.NET is a wrapper around the <code>RealProxy</code> class and <code>IRemotingInfo</code>
			interface.<br>
			DynamicProxy.NET provides an easy and simple interface to handling proxy 
			invocations, plus it offers support for strict/loose type support (useful for 
			when you cast the proxy to other types than those supported by the object being 
			proxied).
		</p>
		<P>This introduction contains more detailed inners of DynamicProxy.NET. If you wish 
			to read a tutorial to proxies and DynamicProxy.NET <a href="tutorial.htm">click 
				here</a></P>
		<h2>Dynamic Proxing</h2>
		<p>To create a DynamicProxy instance you use the <code>DynamicProxyFactory</code>'s <code>
				CreateProxy()</code> method.<br>
			To work with DynamicProxy.NET you need to be aware of a special requirement 
			that DynamicProxy.NET has:
		</p>
		<P align="center">
			<TABLE id="Table1" cellSpacing="1" cellPadding="1" border="1">
				<TR>
					<TD><FONT size="4"><STRONG>Requirement: <EM>DynamicProxy.NET requires your code&nbsp;to use 
									interface based implementation</EM></STRONG><EM>&nbsp;</EM></FONT>
					</TD>
				</TR>
			</TABLE>
		</P>
		<P align="left">What this mean is that you seperate interface and implementation, 
			so you for instance have an interface called ISimpleInterface which defines the 
			methods. You then create a class, for instance called SimpleClass, which 
			implements the interface ISimpleInterface. .NET supports implementing more than 
			one interface and&nbsp;DynamicProxy.NET also supports proxying of more than one 
			interface.</P>
		<pre>		TestClasses.SimpleClass testClass = <FONT color=#3300ff>new</FONT>  TestClasses.SimpleClass();
		TestClasses.ISimpleInterface testClassProxy = <BR>					(TestClasses.ISimpleInterface) DynamicProxyFactory.Instance.CreateProxy(testClass, <FONT color=#3300ff>new</FONT> InvocationDelegate(InvocationHandler));
		</pre>
		<p>The InvocationHandler is a InvocationDelegate, which handles the invocation of 
			the proxy in a reflective manner.<br>
			The signature for the InvocationDelegate looks like the following:<br>
			<code><FONT color="#3300ff">public delegate object</FONT> InvocationDelegate(<FONT color="#3300ff">object</FONT>
				target, MethodBase method, <FONT color="#3300ff">object</FONT> [] parameters)<BR>
			</code>
			<br>
			Eample of a Console logging invocation delegate:
		</p>
		<pre>		<FONT color=#3300ff>private static object</FONT> InvocationHandler(<FONT color=#3300ff>object</FONT> target, MethodBase method, <FONT color=#3300ff>object</FONT>[] parameters) {
			Console.WriteLine("Before: " + method.Name);
			<FONT color=#669966>// Call the real method reflectively
</FONT>  
			   
			    
			<FONT color=#3300ff>object</FONT> result = method.Invoke(target, parameters);
			Console.WriteLine("After: " + method.Name);
			<FONT color=#3300ff>return</FONT> result;
		}
 		</pre>
		<P>The InvocationHandler is called everytime a method is called on the proxy 
			object. The InvocationHandler receives three parameters for each invocation:
		</P>
		<P>- target: Which is a reference to the real object being proxied. In this example 
			the target will refer to the SimpleClass instance.<BR>
			- method: Is the method instance for the method that was called.<BR>
			- parameters: Is an array containing all the parameters that was given to the 
			method</P>
		<P>If for instance the Method4(int inValue) is called is called with the argument 
			10, the parameters the InvocationHandler() will be:</P>
		<P>- target: The SimpleClass instance<BR>
			- method: An instance of the Method4 reflective method<BR>
			- parameters: Is an array with one element, which is an integer with the value 
			10.</P>
		<P>To actually call the real method on the SimpleClass you will have to use the 
			reflection API: <FONT color="#3300ff">object</FONT> result = 
			method.Invoke(target, parameters);</P>
		<H2>Strict/Loose type support</H2>
		<p>DynamicProxy.NET also supports both strict and loose type support. Per default 
			the type support is loose. The type support can be specified through the <code>CreateProxy()</code>
			method in <code>DynamicProxyFactory</code> or via properties on the proxyied 
			object, through the <code>IDynamicProxy</code> interface.
		</p>
		<pre>		<FONT color=#3300ff>public object</FONT> CreateProxy(<FONT color=#3300ff>object </FONT>target, InvocationDelegate invocationHandler)
		<FONT color=#3300ff>public object</FONT> CreateProxy(<FONT color=#3300ff>object</FONT> target, InvocationDelegate invocationHandler, <FONT color=#3300ff>bool</FONT> strict)
		<FONT color=#3300ff>public object</FONT> CreateProxy(<FONT color=#3300ff>object</FONT> target, InvocationDelegate invocationHandler, <FONT color=#3300ff>bool</FONT> strict, Type[] supportedTypes)
		</pre>
		<p>If <code>strict</code> is true then each cast is checked for type compliance 
			against the types supported by the proxied object (<code>target</code> ) and 
			the (if specified) list of <code>supportedTypes</code>.<br>
			Through the <code>IDynamicProxy</code> interface you can access the following 
			properties
		</p>
		<pre>		<FONT color=#009900>/// &lt;summary&gt;
		/// Interface for a dynamic proxy. Through this interface you can work on the proxy instance.
		/// &lt;/summary&gt;</FONT>
		public interface IDynamicProxy {
			<FONT color=#009900>/// &lt;summary&gt;
			/// The target object for the proxy (aka. the proxied object)
			/// &lt;/summary&gt;</FONT>
			<FONT color=#3300ff>object ProxyTarget</FONT> {
				<FONT color=#3300ff>get</FONT>;
				<FONT color=#3300ff>set</FONT>;
			}

			<FONT color=#009900>/// &lt;summary&gt;
			/// The delegate which handles the invocation task in the dynamic proxy
			/// &lt;/summary&gt;</FONT>
			<FONT color=#3300ff>InvocationDelegate InvocationHandler</FONT> {
				<FONT color=#3300ff>get</FONT>;
				<FONT color=#3300ff>set</FONT>;
			}

			<FONT color=#009900>/// &lt;summary&gt;
			/// Type support strictness. Used for cast strictness
			/// &lt;/summary&gt;</FONT>
			<FONT color=#3300ff>bool Strict</FONT> {
				<FONT color=#3300ff>get</FONT>;
				<FONT color=#3300ff>set</FONT>;
			}

			<FONT color=#009900>/// &lt;summary&gt;
			/// List of supported types for cast strictness support. Is only checked if Strict is true
			/// &lt;/summary&gt;</FONT>
			<FONT color=#3300ff>Type[] SupportedTypes</FONT> {
				<FONT color=#3300ff>get</FONT>;
				<FONT color=#3300ff>set</FONT>;
			}
		}
		</pre>
		<h2>Example</h2>
		Given the following interface<br>
		<pre>	<FONT color=#009900>/// &lt;summary&gt;
	/// Interface for the SimpleClass (since you have to program against interfaces with the Dynamic proxy)
	/// &lt;/summary&gt;</FONT>
	<FONT color=#3300ff>public interface</FONT> ISimpleInterface {
		<FONT color=#3300ff>void</FONT> Method1();
		<FONT color=#3300ff>string</FONT> Method2();
		<FONT color=#3300ff>int</FONT> Method3();
		<FONT color=#3300ff>int</FONT> Method4(<FONT color=#3300ff>int</FONT> inValue);
		<FONT color=#3300ff>void</FONT> Method5(<FONT color=#3300ff>int</FONT> inValue, <FONT color=#3300ff>out int</FONT> outValue);
		<FONT color=#3300ff>void</FONT> Method6(<FONT color=#3300ff>ref int</FONT> value);
	}
		</pre>
		and a class <code>SimpleClass</code> that implements it<br>
		<code><FONT color="#3300ff">public class</FONT> SimpleClass : ISimpleInterface</code><br>
		using the InvocationHandler from above, which is a InvocationDelegate delegate, 
		we can proxy a SimpleClass instance in the following way:<BR>
		<BR>
		&nbsp;<FONT face="Courier New" size="2">&nbsp;&nbsp; TestClasses.SimpleClass 
			testClass = <FONT color="#3300ff">new</FONT> TestClasses.SimpleClass();
			<BR>
			&nbsp;&nbsp;&nbsp; TestClasses.ISimpleInterface testClassProxy = 
			&nbsp;(TestClasses.ISimpleInterface) 
			DynamicProxyFactory.Instance.CreateProxy(testClass, <FONT color="#3300ff">new</FONT>
			InvocationDelegate(InvocationHandler));</FONT>
		<BR>
		<br>
		Notice the use of the <code>ISimpleInterface</code> when coding against the 
		proxy. This is required, since you can't program against the SimpleClass, since 
		it's not an interface and the result from the <code>CreateProxy()</code> is a <code>
			TransparentProxy</code> which isn't the same same as the SimpleClass.<br>
		<b>Therefore: Code against interfaces when you proxy an object<BR>
			<BR>
		</b>With the proxy instance <code>testClassProxy</code> you can call the 
		methods on the proxied object:<br>
		<code>
			<BR>
			&nbsp;&nbsp;&nbsp;&nbsp; textClassProxy.Method1()</code><br>
		<BR>
		Using the Invocation handler from above, the call to <code>Method1</code> on 
		the <code>testClassProxy</code> will first write out some information to the <code>Console</code>, 
		then call the real <code>Method1()</code> on the <code>testClass</code> object.<br>
		<br>
		You can decide exactly what happens during a proxy method call by creating your 
		own <code>InvocationDelegate</code> delegate. This way you could build an 
		Interception framework or even an AOP framework if you wish.
		<h2>License</h2>
		<BLOCKQUOTE dir="ltr" style="MARGIN-RIGHT: 0px">
			<p>LGPL.
				<BR>
				<BR>
				<b><u>Disclaimer:</u></b><br>
				This software is provided "as is" without warranty of any kind,<br>
				either expressed or implied. The entire risk as to the<br>
				quality and performance of the software is with you. Should the<br>
				software prove defective, you assume the cost of all necessary<br>
				servicing, repair, or correction. In no event shall the author,<br>
				copyright holder, or any other party who may redistribute the<br>
				software be liable to you for damages, including any general,<br>
				special, incidental, or consequential damages arising out of<br>
				the use or inability to use the software (including, but not<br>
				limited to, loss of data, data being rendered inaccurate, loss of<br>
				business profits, loss of business information, business<br>
				interruptions, loss sustained by you or third parties, or a<br>
				failure of the software to operate with any other software) even<br>
				if the author, copyright holder, or other party has been advised<br>
				of the possibility of such damages.
				<br>
			</p>
		</BLOCKQUOTE>
		<h2>Download</h2>
		<P><EM>Compiled for .NET version 1.1. Should work under 1.0 as well.</EM></P>
		<p>Binary version:<a href="dynamicproxynet.zip">Click here</a><BR>
			Binary and Sourcecode version (includes <a href="http://www.unit.org">NUnit</a> 
			version 2): <A href="dynamicproxynetsrc.zip">Click here</A><BR>
		</p>
		� Copyright 2003 Jeppe Cramon
	</body>
</html>

By viewing downloads associated with this article you agree to the Terms of use and the article's licence.

If a file you wish to view isn't highlighted, and is a text file (not binary), please let us know and we'll add colourisation support for it.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

About the Author

SKI_BUM

Web Developer

Denmark

Member

10 years experience in software design. In my job as a software architect I work with Java and J2EE. .net is so far only a hobby project, but nonetheless interesting Wink | ;-)

Learn how easy it is to create Dynamic/Transparent proxies in .NET using DynamicProxy.NET

Type	Article
Licence
First Posted	16 Oct 2003
Views	165,374
Bookmarked	76 times

.NET1.0.NET1.1C#
WindowsVisual-Studio, +

		9,892,815 members (28,444 online) Visit CodeProject.TV Discuss CodeProject.TV Sign in Email Password Forgot your password? Sign in using