What is Reflection in .NET? Namespace?

 How will you load an assembly which is not referenced by current assembly?
All .NET compilers produce metadata about the types defined in the modules they produce. This metadata is packaged along with the module (modules in turn are packaged together in assemblies), and can be accessed by a mechanism called reflection. The System.Reflection namespace contains classes that can be used to interrogate the types for a module/assembly.
Using reflection to access .NET metadata is very similar to using ITypeLib/ITypeInfo to access type library data in COM, and it is used for similar purposes - e.g. determining data type sizes for marshaling data across context/process/machine boundaries.
Reflection can also be used to dynamically invoke methods (see System.Type.InvokeMember), or even create types dynamically at run-time (see System.Reflection.Emit.TypeBuilder).
Reflection generally means that a program can gain knowledge about its own structure. With .NET, Reflection describes the possibility - depending on security features - to detect mega data of a .NET-application and of the data types and functions contained therein.
During the runtime, it is therefore possible that an application can determine its own functionality. For example, an application could be developed, which can be extended by functionality through the adding of the respective Assemblies - without changing the main program.