How to resolve Out of memory exception in WP7 using dictionary?

Question

I build an application in WP7 where i require to load around 20000 hard coded data({'a',"XYZ"},{'b',"mno"},....)on which i have to perform the search. So i trying to do this by creating a dictionary making 'a' as key and value as "XYZ". As soon as my dictionary gets filled it gives Out of memory exception. How can i solve this problem considering that im building WP7 application? Or Is there some way other than using dictionary?

Answer 1

Whenever you are loading so much data onto a phone , you're doing it wrong. Firstly, the bandwidth issue is going to kill your app. Second, the memory issue has already killed your app. Thirdly, the CPU issue is going to kill your app. The conclusion is, your user ends up killing your app.

Recommended solution: find a way to categorize the data so that not all of it must download to the phone. Do your processing on the server where it belongs (not on a phone).

If you insist on processing so much data on the phone, first try to manage the download size. Remember you're talking about a mobile phone here, and not everywhere has max 3G speeds. Try to compress the data structure as much as possible (eg using a tree to store common prefixes). Also try to zip up the data before downloading.

Then count your per-object memory usage aggressively. Putting in 20,000 strings can easily consume a lot of memory. You'd want to reduce the size of per-object memory usage as possible. In your example, you are just putting strings in there, so I can't guess how you'd be using up the tens of MB allowable on a WP7 app. However, if you are putting not just strings, but large objects, count the bytes.

Also, manage fragementation aggressively. The last thing you'll want to do is to new Dictionary() then dict.Add(x,y); in a for-loop. When the dictionary's internal table space runs full, it gets allocated to a new place, and the entire dictionary copied to the new place, wasting the original space. You end up having lots of fragmented memory space. Do a new Dictionary(20000) or something to reserve the space first in one go.

Answer 2

Instead of storing it in memory as a Dictionary you can store it in a Database ( wp7sqlite ) and fetch only the data required.In this way you can store whatever amount of data.

Edit

No nothing is required in extra from user end.you can create the database using sqlite manager ,attach this to the project.Copy DB to Isolated storage on first usage.and you can access the DB whenever you want .Check this Link DB helper .This link uses sqlitewindowsphone instead of WP7Sqlite.I prefer wp7sqlite Since i got an error using sqlitewindowsphone.