Read Only fields (readonly)

• Read only fields are constants.
  
• A Read only field can't be modified once initialize.
  
• Read only fields are declared using the readonly keyword.
  
• They are initializing in its declaration or in a constructor.
  

  E.g.: public class Test
  

  {
  

  public static readonly double dNum = Math.Sin (Math.PI);
  

  public readonly string sStrOne;
  

  public Test (string sStr)
  

  {
  

  sStrOne = sStr;
  

  }
  

  }