Read Only

Read Only Fields

When the value of a field is only visible outside the class it is called a read only property.
The value of the field can only be changed inside the class.

public class Animal 
{ 
   private readonly int _Age; 
} 

The readonly keyword is used to declare a constant that can be defined in its declaration or at run-time in the constructor.
This value cannot be changed after the class has been created.
The const keyword is used to declare a constant that must be defined in its declaration.

A read-only field is similar to a const and can also represent values that do not change
A read-only field can either be initialized at the declaration or in a constructor.
A read-only field can be complex types.

A read only field that contains an object can have its properties modified at run-time

A private set property can be called after the class has been created.

Read Only Properties

To create a read-only property you can exclude the set altogether.

public class Animal 
{ 
   private int _Age; 

   public int Age 
   { 
      get { return this._Age; } 
   } 
} 

Alternatively if you still needed to set the value inside the class then you can change it to private.

public class Animal 
{ 
   private int _Age; 

   public int Age 
   { 
      get { return this._Age; } 
      private set { this._Age = value; } 
   } 
}