Developer Solutions for Web and Other

In a previous post, dotNET - Under the Hood, IL Assembly , I briefly described how to write some IL Code to an Assembly, but what if at a later occasion you'll want to invoke these methods from the dll. This could be achieved by loading the assembly in an AppDomain and then invoking the methods within ???? Or you could use what are known as DynamicMethod s to invoke the methods. DynamicMethod is a class that also resides in the System.Reflection.Emit namespace. Why would you want to use DynamicMethod? it's useful when you want to load methods into memory or write methods in memory and invoke later. We can write IL code in memory in the exact same was as we wrote IL code earlier using the MethodBuilder. In my experience DynamicMethod is a bit tricky to get right especially when you try to invoke your Dynamic method. The problem I found was with the constructor parameters, what do they mean; There are 6 constructor overloads in all; half of these are associated with an class in...

You've all used the foreach loop in .NET to get the values in a container. The foreach actually uses that objects Enumerator. In order to allow the use of the foreach on an object the class must implement the IEnumerable.GetEnumerator method which also means you have to implement the IEnumerable interface. Within the GetEnumerator override you need to return an instance of IEnumerator, so you need to create a class that implements the IEnumerator interface. see the code. This is useful if you class contains a member variable which is an or even a container. Let's say it's an array. When an instance of your class is create the array is also instantiated. But you don't want the array to be visible but you do want clients to be able to use a foreach on your class instance, this can be achieved by implementing the IEnumerable interface and overriding the GetEnumerator method. using System; using System.Collections.Generic; using System.Text; using System.Collections; namesp...

Code Security is all about allowing and preventing code from running. The . NET Security Model works by the assemblies each having their own Evidence embedded in the Assembly by the Assembly writer. When the CLR loads the assembly it then reads and applies this Evidence to a Security model and this in turn returns Permissions , depending on what Permissions are returned will determine is the assembly is permitted to execute or not. So it's Evidence in (on the assembly) -> Code Groups -> Permissions. Code Access Security (CAS) is the the mechanism used by .NET to manage all of this. It's function is to process assemblies and determine the runtime permissions they should have, e.g. should they code within a certain assembly be allowed to run or not. All assemblies have Evidence. As the CLR is loading the assembly it looks at this Evidence and processes it using the current machines .NET Code Group. Depending on where the assembly is being loaded from, the Evidence it has,...

IL (Intermediate Language) is also referred to as MSIL (Microsoft Intermediate Language) or even ILAsm which is the same thing. IL is the code which your source code (C#, VB.NET etc) is compiled into. When you EXE or DLL is run these IL code is converted to a machine language particular to the present machine i.e. if the current machine being used to run the application is a Windows 2000 machine the IL will be converted into Windows instructions before running on the x86 processor (processor architecture used for Windows machines). When you're developing with .NET languages with a Development tool such as Visual Studio 2005 the compiler you use will generate the correct/valid IL for you, but what if you want to create your own IL for some reason! One reason could be that you've developed your own Language and would like it to run on .NET, in this case you'll need to write out some sort of Assembly, be it EXE or DLL, with IL code. To do this you can use some Classes availa...