The dynamic language runtime (DLR) is introduced in .NET framework 4.0
The dynamic language runtime (DLR) is a new runtime environment that adds a set of services for dynamic languages to the CLR. The DLR makes it easier to develop dynamic languages to run on the .NET Framework and to add dynamic features to statically typed languages. To support the DLR, the new System.Dynamic namespace is added to the .NET Framework.
The namespace is as follows -