private constructor

A private constructor is a special instance constructor. It is generally used in classes that contain static members only. If a class has one or more private constructors and no public constructors, other classes (except nested classes) cannot create instances of this class. 
For example:

public class Counter
{
    private Counter() { }
    public static int currentCount;
    public static int IncrementCount()
    {
        return ++currentCount;
    }
}

class TestCounter
{
    static void Main()
    {
        // If you uncomment the following statement, it will generate 
        // an error because the constructor is inaccessible: 
        // Counter aCounter = new Counter();   // Error

        Counter.currentCount = 100;
        Counter.IncrementCount();
        Console.WriteLine("New count: {0}", Counter.currentCount);

        // Keep the console window open in debug mode.
        Console.WriteLine("Press any key to exit.");
        Console.ReadKey();
    }
}
// Output: New count: 101

 When we declare a class constructor as private , we can not do 2 things:-

1. We can not create a object of the class.
2. We can not inherit the class.

Static Constructor C#

Static Constructor:-

 A static constructor is used to initialize any static data, or to perform a particular action that needs to be performed once only. It is called automatically before the first instance is created or any static members are referenced.

Example

class SimpleClass
{
    // Static variable that must be initialized at run time.
    static readonly long baseline;

    // Static constructor is called at most one time, before any
    // instance constructor is invoked or member is accessed.
    static SimpleClass()
    {
        baseline = DateTime.Now.Ticks;
    }
}

Static constructors have the following properties:

• A static constructor does not take access modifiers or have parameters.
  
• A static constructor is called automatically to initialize the class before the first instance is created or any static members are referenced.
  
• A static constructor cannot be called directly.
  
• The user has no control on when the static constructor is executed in the program.
  
• A typical use of static constructors is when the class is using a log file and the constructor is used to write entries to this file.
  
• Static constructors are also useful when creating wrapper classes for unmanaged code, when the constructor can call the LoadLibrary method.
  
• If a static constructor throws an exception, the runtime will not invoke it a second time, and the type will remain uninitialized for the lifetime of the application domain in which your program is running.
  
  Thanks & Regards
  Alok Kumar Sharma 
  

What is Early & Late Binding in C#

Early Binding :-
    Calling a non-Virtual method,decided at a compile time is known as early binding.
Late Binding
    Calling a virtual method (Pure polymorphism),decided at run-time is known as Late binding.

Thanks & Regards
Alok Kumar Sharma

.NET Framework Version History

.NET Version	Introduced with IDE	Features Detail	CLR Version
4.6	Visual Studio 2015	.Introduced RyuJIT, a new JIT compiler for 64-bit systems .Introduced Open Source.Net Framework Packages .Support for Code page encodings .Improvements to event tracing	4.0
4.5.1	Visual Studio 2013	·  Includes performance and debugging improvements ·  Support for automatic binding redirection ·  Expanded support for Windows Store apps	4.0
4.5	Visual Studio 2012	·  Features Enhancements to CLR 4.0 ·  Async Support ·  Support for building Windows Store apps ·  Features Enhancement to WPF, WCF, WF, and ASP.NET	4.0
4.0	Visual Studio 2010	·  Introduced CLR 4.0 ·  Managed Extensibility Framework (MEF) ·  Dynamic Language Runtime (DLR) ·  Task Parallel Library	4.0
3.5	Visual Studio 2008	·  Built-In AJAX Support ·  LINQ ·  Dynamic Data ·  Multi-targeting Framework Support	2.0
3.0	Visual Studio 2005	·  Windows Presentation Foundation (WPF) ·  Windows Communications Foundation (WCF) ·  Windows Workflow Foundation (WF), and CardSpace	2.0
2.0	Visual Studio 2005	·  Introduced CLR 2.0 ·  Generics and generic collections ·  Partial classes ·  Nullable types ·  Anonymous methods ·  Introduced many new controls and features to ASP.NET	2.0
1.1	Visual Studio.NET 2003	·  Features Enhancement to ASP.NET and ADO.NET ·  Built-in support for mobile ASP.NET controls ·  Security Enhancement ·  Built-in support for ODBC and databases ·  Internet Protocol version 6 (IPv6) support	1.0
1.0	Visual Studio.NET	·  Introduced CLR 1.0 ·  Support for Object-oriented Web application development ·  Use of DLL class libraries	1.0