variable scope in C#

Hi Expert,

Why I cannot access variable e in Method C?


class A
{

Entity1 e;

public method B()

{ e= new student;

  e.Id=1
  database.addtoStudent(e);

   call method C

}

public method C()

{ 
  e.address; 
  database.savechanges(0)
}


}

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dshi15Asked:
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Fernando SotoRetiredCommented:
Seeming that e is defined at class level it should be accessible from anywhere in the class A. So what exception are you getting? Of course this means that e was initialized before method c is called otherwise you will get an exception.
dshi15Author Commented:
here is error

Only assignment, call, increment, decrements, and new object expressions can be used as a statement,
Fernando SotoRetiredCommented:
So in other words e is defined at class level but has not yet been initialized, therefore having a null value. If you attempt to access e now as method c it will attempt to assign a value to the address property to e but e is null and will throw an exception. If you call method B first it will create a new Student and assign it to e, as long as Student is assignable to type Entity1 like in being a subclass of Entity1 type and then calling method C it should work.
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Fernando SotoRetiredCommented:
The line e.address;, is not a complete statement. Statements like the following would make it legal.

e.address = "The value to assign to e.address";
or
var address = e.address;

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dshi15Author Commented:
thank you and i got it, when i finished type all thing, the error gone.
Fernando SotoRetiredCommented:
Not a problem dshi15, glad I was able to help.
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