YOU can use the Code Access Security Tool (Caspol.exe) to turn security on and off.

To turn off security, type the following command at the command prompt:
caspol -security off

To turn on security, type the following command at the command prompt:
caspol -security on

In the .NET Framework 4.0, for using Caspol.exe, you first need to set the element totrue.

Garbage collection prevents memory leaks during execution of programs. Garbage collector is a low-priority process that manages the allocation and deallocation of memory for your application. It checks for the unreferenced variables and objects. If GC finds any object that is no longer used by the application, it frees up the memory from that object.

GC has changed a bit with the introduction of .NET 4.0. In .NET 4.0, the GC.Collect() method contains the following overloaded methods:
GC.Collect(int)
GC.Collect(int, GCCollectionMode)

Another new feature introduced in .NET is to notify you when the GC.Collect() method is invoked and completed successfully by using different methods. The .NET 4.0 supports a new background garbage collection that replaces the concurrent garbage collection used in earlier versions. This concurrent GC allocates memory while running and uses current segment (which is 16 MB on a workstation) for that. After that, all threads are suspended. In case of background GC, a separate ephemeral GC - gen0 and gen1 can be started, while the full GC - gen0, 1, and 2 - is already running.

There are two key concepts of CAS security policy- code groups and permissions. A code group contains assemblies in it in a manner that each .NET assembly is related to a particular code group and some permissions are granted to each code group. For example, using the default security policy, a control downloaded from a Web site belongs to the Zone, Internet code group, which adheres to the permissions defined by the named permission set. (Normally, the named permission set represents a very restrictive range of permissions.)

Assembly execution involves the following steps:
1. Evidences are gathered about assembly.
2. Depending on the gathered evidences, the assembly is assigned to a code group.
3. Security rights are allocated to the assembly, depending on the code group.
4. Assembly runs as per the rights assigned to it.

Following are the differences between namespace and assembly:
• Assembly is physical grouping of logical units, Namespace, logically groups classes.
• Namespace can span multiple assembly.

A piece of managed code is executed as follows:
• Choosing a language compiler
• Compiling the code to MSIL
• Compiling MSIL to native code
• Executing the code.