LINQ Queries And Context

Question

Hello SO,

I have a slight issue with some code I'm writing

if(parameter == 1)
{
 var linq = from a in db.table select a;
}
else
{
 var linq  = from a in db.table where a.id = 1 select a;
}

foreach(var b in linq)
{
...
}

So basically what's going on is that the variable "linq" is different depending on the value of "parameter". When I try to loop through "linq" with my foreach loop, I get an error about how linq doesn't exist in the current context.

What is the best way to work around this type of issue?

Answer 1

What you tried doesn't work because the variable linq is already out of scope when you try to use it. You need to move the declaration to the outer scope.

To answer your question in a general way first: if you need to declare a variable before you assign to it, you can't use var. You need to declare the type explicitly:

IQueryable<Something> linq;
if(parameter == 1)
{
    linq = from a in db.table select a;
}
else
{
    linq = from a in db.table where a.id == 1 select a;
}

In your particular example though you can simplify things:

var query = from a in db.table select a;
if (parameter != 1)
{
    query = query.Where(a => a.id == 1);
}

Answer 2

I dunno if this is the best way but, assuming you're returning the same table.

var linq  = from a in db.table where a.id = 1 select a;

if(parameter == 1)
{
 linq = from a in db.table select a;
}

//foreach.

You can reconstruct your linq query and not pay a big penalty, since you haven't actually executed it.