• IEnumerable is an interface available in the System.Collection namespace
• Any collection that implements the IEnumerable implements the GetEnumerator method of the IEnumerable interface, making it iterable.
• The IEnumerable or the Generic IEnumerable must be used over in-memory objects.

• We can compile .NET Framework projects without using Visual Studio on the Command Line using csc.exe file.
• We can supply additional arguments to csc.exe, in-addition to the csproj file of the .NET project.
• In .NET Core, we use the dotnet build command on the command-line which can build the csproj without using Visual Studio.

• A JIT (Just-In-Time) compiler converts the MSIL (MS Intermediate Language) into native code on demand during the application runtime, when the application components are loaded and executed.
• The JIT compilation happens specific to the running CPU architecture, since the common language runtime supplies a JIT compiler for each supported CPU architecture.
• If the managed code calls platform-native APIs or runs platform-specific assemblies, the JITed code runs on only that particular system.

• A Tuple is a data structure which can hold data of multiple types in a single variable.
• Tuple was first introduced in .NET 4.0.
• A Tuple can generally represent a row in a database table, where each column can represent a different type.
• Individual values of "Items" inside a single tuple variable can be accessed by means of properties (Item1, Item2, ..)
• A tuple can hold a maximum of 8 Items in itself, where the individual Items can themselves be Tuples of different items.

var tuple = new Tuple<T1, T2, T3, ... , T7, T8>();

• GAC stands for Global Assembly Cache
• It is a place in the Windows directory where the assemblies (the DLL files) designated to be shared by the applications are stored for reuse.
• Any assembly or component which is desired to be shared across applications in a machine is registered on the Global Assembly Cache.
• To register an assembly into the Global Assembly Cache, we can do so by using the GACUtil.exe as below:

> gacutil -i [Path][Assembly Name].dll

Namespaces are used to group and organize classes which are somewhat related to each other. Any class created would reside under a namespace and is referenced using the namespace in other classes or modules.

namespace MyModule {
  class MyClass {
   // all things under class
  }
  class MyOtherClass {
   // all things under class
  }
}

• Both SingleOrDefault() and FirstOrDefault() LINQ methods return default value of the passed collection data type when there are no matching elements found for the condition predicate.
• Both methods return only one record from the collection that matches the predicate.
• SingleOrDefault() expects the condition predicate to match only one record in the set - for example, a postUrl in a collection of BlogPost objects. If there are more than one objects that match the predicate, SingleOrDefault() method throws exception.
• Whereas the FirstOrDefault() method returns the first object in the collection that matches the prerequisite and so no such exception is thrown.

Adapter is used in cases when we need to use two incompatible interfaces. The adapter provides the client what interface it needs while the adapter internally calls the other interface.