CODEWITHSUNDEEP
c#.netsqlsql-serverwindows
James
James

Reputation: 257

Linq to SQL brief question

I have a query below. although can anyone point out what "from p" means? and also "var r"?

DataClasses1DataContext db = new DataClasses1DataContext(); 
            var r = from p in db.Products 
                    where p.UnitPrice > 15 // If unit price is greater than 15...
                    select p; // select entries

Upvotes: 2

Views: 174

Answers (3)

Marc Gravell
Marc Gravell

Reputation: 1062510

r is the composed query - an IQueryable<Product> or similar; note the query has not yet executed - it is just a pending query. var means "compiler, figure out the type of r from the expression on the right". You could have stated it explicitly in this case, but not all. But it wouldn't add any value, so var is fine.

p is a convenience marker for each product; the query is "for each product (p), restricting to those with unit price greater than 15 (where p > 15), select that product (select p) as a result.

Ultimately this compiles as:

IQueryable<Product> r =
    db.Products.Where(p => p.UnitPrice > 15);

(in this case, a final .Select(p => p) is omitted by the compiler, but with a non-trivial projection, or a trivial query, the .Select(...) is retained)

Upvotes: 3

Haris Hasan
Haris Hasan

Reputation: 30097

from p means any record from db.Product and var r means the collection of p

overall whole statements means give me all those records(p) from db.Products where p.UnitPrice is greater than 15

see this question to know more about var

Upvotes: 0

Oded
Oded

Reputation: 498904

The p means each specific item in the collection referenced (db.Products). See from on MSDN.

var is syntactic sugar - it resolves to the type returned from the LINQ query, assigning the type to the variable r. See var on MSDN.

For better understanding of LINQ, I suggest reading through 101 LINQ Samples.

Upvotes: 1

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