ReadOnly modifier used on a list

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what would happen by using the readonly modifier on the list container.

For example:

C#

class Test
{
  private readonly list<string> stringTest = new List<string>();

test()
{}

void changeStringTest()
{
  stringTest.Add("hello");
//Why i am allowed to do this. Readonly should prevent me from doing this by definition where i should only modify the list in the constructor or during initialization 
}

}

Also what is then the difference of readonlycollection<string>

Thanks in Advance

Posted 6-Nov-12 18:35pm

jackel7777

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SoumenBanerjee 7-Nov-12 1:17am

View this link
http://msdn.microsoft.com/en-us/library/ms132474.aspx

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Farzan Hajian · Answer 1 · 2012-11-06T21:17:00

When you apply "readonly" keyword to a reference, you prevent the reference from changing the object it is pointing to but it is legal to change the object itself.
In your case, when stringTest is first initialzed, you are not allowed to create a new List<string> object and assign it to stringTest later in your application.

C#

class Test
{
  private readonly list<string> stringTest = new List<string>();

  test(){}
 
  void changeStringTest()
  {
     /* NOT ALLOWED. stringTest is readonly. Its not allowed to change
        the object it is pointing to. */
     stringTest = new List<strnig>();
     
     /* ALLOWED. You are not going to change stringTest but the object.
        Because adding a new item to a list does not affect the
        reference (stringTest) but the object whitch is pointed to by
        stringTest. */
     stringTest.Add("hello");
  }
}
</strnig></string></string>