linq and refrence object

Question

 

hi everybody

I have a method by following signature and body:
private void LoadByItem(Item item)
{
MyDBDataContext my = new MyDBDataContext();
var query = from q in my.Items
where q.Id == item.Id
select q;
item = query.First<Item>>;
}
when I send the argument to the above method, after method process I get nothing in item while in the method item had value. I think after assigning item to query it work as a value type not a reference type.
please let me know how can I get the reference of item without using ref in function signature.

Answer 1

Hi toorani,

So you problem is how to output the parameter Item in your Method above, is not it?

As far as I know, there is two type variable in C#, reference type and value type, it you use the reference type, you can pass it by reference without the ref key word, and any class in C# in a reference type, if you define the Item as class, you can implement the function what you want.

Code Snippet

Item item1 = new Item();

LoadByItem(item1); //output the parameter ok

class Item

    {

      public  int test_value;

    }

 

Alternative solution for ref key word, the out key word has the same result.

Regards,

Xun

 

Answer 2

I have done the test and in my case works fine. try use DataContext.Log or use a profiler to see if the query is executed, and ensure that the query performed returns record. Maybe that is the problem.

Another thing

item = query.First<Item>>; this is wrong
gives the error Cannot convert method group 'First' to non-delegate type

use
 item = query.First<Item>();