How to defined a local variable scope of var outside the if statement?

Question

In my previous code, I try in the view. I think I will need to check first if the id is empty or null then set the value equal to 0 but I got an error, says, accessing local variable is not allow. But how can I access a local variable of var inside of if statement?

var Rs1;
if (id != null)
{
    Rs1 = _context.DwPropertyDetails.Select(x => new
    {
        Rs1Clm2 = totalTransAmount,
        Rs1Clm3 = x.Studio),
        Rs1Clm4 = x.OneBedroom),
        Rs1Clm5 = x.TwoBedroom),
        Rs1Clm6 = x.ThreeBedroom),
        Rs1Clm7 = x.Total),
    });
}
else
{
    Rs1 = _context.DwPropertyDetails.Select(x => new
    {
        Rs1Clm2 = 0,
        Rs1Clm3 = 0,
        Rs1Clm4 = 0,
        Rs1Clm5 = 0,
        Rs1Clm6 = 0,
        Rs1Clm7 = 0,
    });
}

For *anonymous type* there is an [ugly workaround](http://stackoverflow.com/a/4708589/1997232) to define its type (for use in `List`). You can't use `var` in such scenario, as it need type to be extract-able from right side of expression. I believe `dynamic` will do, but it comes without intellisense support. — Sinatr, Feb 20 '17 at 08:51

score 2 · Answer 1 · answered Feb 20 '17 at 08:44

2

var infers the type. If you don't assign a value, it can't infer the type of the value.

You have to create a class or struct and put your fields in there. Then use the type of the created class.

answered Feb 20 '17 at 08:44

Patrick Hofman

153,850
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hmm .. Good to hear that. Can you give me an example? Please. – Stephen Shuane Feb 20 '17 at 08:46
`var x = "a";`. Hover over `var` and you will see it says "string". – Patrick Hofman Feb 20 '17 at 09:01

score 1 · Answer 2 · answered Feb 20 '17 at 08:51

If you really want to use var:

 var Rs1 = id != null ?
             _context.DwPropertyDetails.Select(x => new
                {
                    Rs1Clm2 = totalTransAmount,
                    Rs1Clm3 = x.Studio,
                    Rs1Clm4 = x.OneBedroom,
                    Rs1Clm5 = x.TwoBedroom,
                    Rs1Clm6 = x.ThreeBedroom,
                    Rs1Clm7 = x.Total,
                })
           : _context.DwPropertyDetails.Select(x => new
                {
                    Rs1Clm2 = 0,
                    Rs1Clm3 = 0,
                    Rs1Clm4 = 0,
                    Rs1Clm5 = 0,
                    Rs1Clm6 = 0,
                    Rs1Clm7 = 0,
                 });

Why not just use the null coalescing operator instead of using the conditional operator? Like so - `Rs1Clm3 = x?.Studio ?? 0,` — ColinM, Feb 20 '17 at 10:12

score -1 · Answer 3 · edited Feb 20 '17 at 09:01

-1

Why not use object instead of var?

var needs to be implicitly typed first. But, since you're assigning an object without a type, might as well just use 'object'.

E.g. object Rs1;

edited Feb 20 '17 at 09:01

Patrick Hofman

153,850
22
249
325

answered Feb 20 '17 at 08:40

mindOfAi

4,412
2
16
27

Yes, Stephen, you should try this – Lali Feb 20 '17 at 08:41
2

Using `object` doesn't allow accessing the properties, so it renders the object useless for the developer. – Patrick Hofman Feb 20 '17 at 09:02
1

*"Why not use `object` instead of `var`?"* - for two reasons: boxing (minus performance) and no intellisense support (minus comfort). Moreover, as here is anonymous type involved, using `object Rs1` makes it completely useless for later, unless you going to cast, but then either you have a concrete type or it's pretty [ugly](http://stackoverflow.com/a/1409776/1997232). – Sinatr Feb 20 '17 at 09:15

How to defined a local variable scope of var outside the if statement?

3 Answers3