0

im trying to work out if you can access an object that was added to a list (of objects) something like this:

public class nearshop_data
{
    public String r_name { get; set; }
    public String r_desc  { get; set; }
    public  String loc_lat  { get; set; }
    public  String loc_lon  { get; set; }
}

then adding to that list as you would 

shop_data = new nearshop_data();
lo = new List<object>();

for (int i = 0; i < count; i++) {

    shop_data.r_name = stuff.results[i].name;
    shop_data.r_desc = stuff.results[i].vicinity;
    shop_data.loc_lat = stuff.results[i].geometry.location.lat;
    shop_data.loc_lon = stuff.results[i].geometry.location.lng;

    lo.Add(shop_data);       

}

then i want to retrieve that in another class say in the code behind and here is where it all fails... as i cant actually access the properties of that object

any ideas on how to rewrite the code or what to use?

I'm guessing when I get the instance of that list in my code behind and lets say retrieve it at index 0 its still boxed in (or am i wrong?) - i vaguely remember something like this was done in java

4

2 回答 2

4

I think the problem is that you're using List<object> instead of List<nearshop_data> which is effectively boxing the type.

If you need to keep it like this you'd need to cast the object to the appropriate type:

nearshop_data firstElement = (nearshop_data)lo[0];

or even better use a List<nearshop_data> in the first place.

In addition because nearshop_data is a reference type, and you only instantiate it once, you are only adding the pointer to the same instance of shop_data each time. Meaning you'll only end up with one element with the values equal to that of the last loop iteration.

于 2013-04-21T16:02:56.343 回答
1

You need to cast the item from the list back to it's specific class:

 nearshop_data myitem = lo[0];

Of course you might want to check the type of the open before you try and cast (otherwise it will throw an exception). You can either do this:

if (lo[0] is nearshop_data) 
{
    // do your cast here
}

or:

nearshop_data myitem = lo[0] as nearshop_data;

if (myitem != null)
{
    // myitem is a nearshop_data instance
}

Of course, better would be to use a more specific class in your generic list. List<object> is really no more useful than the old ArrayList. If you only need nearshop_data items then just use List<nearshop_data>. If you need a hetreogenous list then just use the most specific base class (or interface) that will cover all the items you need to store.

于 2013-04-21T16:05:48.643 回答