Question

Basically I wanted to have an if-else statement in my linq to sql statement.

var query = from d in database
            if(x == y) {
                where d.Attr = x
            }
            else {
                 where d.Attr = y
            }
            select d;

Any ideas?

Answer 1

Isn’t that just the same as

var query = from d in database
            where d.Attr == y
            select d;

Your situation (or a similar, more realistic one) can be handled with a simple conditional in the where clause. For more complex queries you can use the extension methods to build up a query implementing conditionals pretty easily or use a PredicateBuilder to create arbitrarily complex conditions.

var query = db.Table;
if (x == y)
{
   query = query.Where( d.Attr == z );
}
else
{
   query = query.Where( d.Attr == t );
}

var predicate = PredicateBuilder.True<Foo>()
                                .And( f => f.Attr == y )
                                .And( f => f.Attr == x )
                                .Or( f => f.Attr == z );
var query = db.Foo.Where( predicate );