Select LINQ的最佳返回类型是什么

Question

I'm just getting started with LINQ and C# and I'm unsure what's the recommended return type for a LINQ statement that returns a bunch of records.

I found the following two notations that work both when linking the data to a gridview. Which approach should I use in what situation?

public object SelectAll()
    {
        var query = from p in dc.Products
                    select new { p.pk_product_id, p.product_name, p.product_price_kg };
        return query;
    }

public IQueryable<Product> SelectAll2()
{
    var query = from p in dc.Products
                select p;
    return query;
}

Answer 1

You don't want to return object . I wonder where you have seen this.
IQueryable<T> or IEnumerable<T> is the preferred way.

Answer 2

If this method only gets called as the SelectMethod of a GridView , then it doesn't matter . The GridView code will be checking at execution time exactly what kind of data it's been given, and deciding what to do with it on the basis of what it is. Strong-typing the method doesn't make any difference to the GridView .

If you're going to be consuming this method from your own code, then use the most specific type that makes sense.

Answer 3

If you are building reusable data access code (and not just a query for a specific form or control) then you should take a look at repository patterns - have a look here .

In this case you would want to return strongly typed entities from the query (and not objects from the result of an anonymous class)

PS : you can shorten SelectAll2 to

return dc.Products.AsQueryable();