Question

See below code snippets

class scopes
{
  static int j=20;
  Console.WriteLine(j);
    public static void Main()
   {
       int j=30;
       Console.WriteLine(j);
       return;
   }
}

For above code , variable hiding is supported
see below code

public static int Main()
{
    int j = 20;
    for (int i=0; i < 10; i++)
    {
        int j = 30;    //can't do this
        Console.WriteLine(j + i);
    }
    return 0;
}

Here for above code variable hiding is not supported.

What is the reason behind this?

Answer 1

In the first case, there is at least a defined way to disambiguate between the two things, i.e. the this. prefix – inside the method, this.j is the field, where-as j is the member. As for why this is supported: speculation, but probably so that adding a field to the class (which could be in a different code file in the case of partial classes) doesn’t cause random methods to start throwing compiler errors. Note that the meaning in of j in the method is identical before and after the field j is added.

In the second case, this is not a concern: adding locals can only impact the single local method, and there is no disambiguation syntax (i.e. which j do we mean), and no risk of accidental breakage from unrelated code.