Use of unassigned variable in switch case in C#

Question

I'm making a basic chat program as a thesis and I've run into this problem.

As you can see on the picture, it gives me an unassigned variable error at line 107, but it works perfectly fine afterwards (like at line 125). The switch case always starts with case 1, in which I create a new UserLogin form called login. After that it decides wether it should go to case 2 or 3. Neither of them has any unassigned variable error except the line 107 one. I don't really have a clue as to why is this happening.

If you commented out line 107, you would probably see the same error on the next line that used `login`. The compiler only flags the first time you use an unassigned variable. — BJ Myers, Mar 24 '16 at 00:48
I've posted a screenshot because the code tag didnt show line numbers. — DarkSide, Mar 25 '16 at 13:43

score 3 · Answer 1 · answered Mar 24 '16 at 00:48

3

That's because the only place the variable gets assigned at is case 1. You need to assign it outside of the switch statement, since there is a possibility that case 1 will never execute, thus, the variable will never be assigned.

answered Mar 24 '16 at 00:48

B.K.

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score 3 · Accepted Answer · answered Mar 24 '16 at 00:48

Even though you know you'll hit case number 1 before hitting 2 or 3, the compiler doesn't.

You need to assign login a value before the switch block, even if it's just null.

login = null;

switch (...)
{
    case 1:
        login = new UserLogin();
        ...

If you know you're always going to hit case 1 first, consider just assigning login a new UserLogin before you even enter the switch statement.

Use of unassigned variable in switch case in C#

2 Answers2