•  Abstraction 

1. Abstraction is "To represent the essential feature without representing the background details."
2. Abstraction lets you focus on what the object does instead of how it does it.
   
3. Abstraction provides you a generalized view of your classes or objects by providing relevant information
   
4. Abstraction is the process of hiding the working style of an object, and showing the information of an object in an understandable manner.

• Encapsulation 
1. Hiding the internal state and functionality of an objec...

We can use DateTime.Now.Ticks and Guid.NewGuid().ToString() to combine together and make a unique id.

As the DateTime.Now.Ticks is added, we can find out the Date and Time in seconds at which the unique id is created.

Please see the code.

var ticks = DateTime.Now.Ticks;
var guid = Guid.NewGuid().ToString();
var uniqueSessionId = ticks.ToString() +'-'+ guid; //guid created by combining ticks and guid

var datetime = new DateTime(ticks);//for checking purpose
var datetimenow = DateTime.Now;    //b...

It will be good if your environment support you to use below method.

[StringLength(150)]
public string MyProperty { get; set; }

You have to include the below namespace to use it.

using System.ComponentModel.DataAnnotations;

A string is a sequential collection of characters that is used to represent text.

A String object is a sequential collection of System.Char objects that represent a string; a System.Char object corresponds to a UTF-16 code unit.

The value of the String object is the content of the sequential collection of System.Char objects, and that value is immutable (that is, it is read-only).

For more information about the immutability of strings, see the Immutability and the StringBuilder class section in ...