Silverlight Isolated Storage and loading big files

In a Windows Phone 7 a开发者_如何转开发pplication, I would like to query a big XML file (list of cities) stored using Isolated Storage. If I do that this way, will the file be loaded to memory (> 5 mo) ? If so, what other solution do I have?

Edit:

More details. I want to use AutoCompleteBox (http://www.jeff.wilcox.name/2008/10/introducing-autocompletebox/), but instead of using a web service (this is fixed data, no need to be online), I want to query a file/database/isolated storage... I have a fixed list of cities. I said in the comments it's 40k, but it finally seems closer to 1k rows.

instead of using isolatedstorage for this, would it be an option for you to use a webservice instead... or do you design your app for an offline approach?

querying a webservice, wcf or json enabled webservice is really simple, and will be easier for you to maintain :)

Rather than have a big file containing all the data can you not break it down into lots of smaller files. (One for each city?)

You could have a separate file to keep an index of them all if need be. Alternatively, depending on the naming of the files, you may be able to use IsolatedStorageFile.GetFileNames to get a list of all files.

I would create my own file format, using, for example, a separator between fields, with one row for each record. That way you can read your file line-by-line to fill your data structure with these advantages:

1. no need to pull the whole file into memory
2. no XML overhead (in a desktop application it may not be a problem, but in the phone context a 5 MB text file may become quite a bit smaller)

Dumb example:

New York City; 12345
Berlin; 25635
...

EDIT: given that the volume is not that large you don't need any form of indexing or loading on-demand. I would store the cities as stated above -one record per line-, load them in a list and use LINQ to select the items you need. This will probably be fast and keep your application very responsive.

In this case, in my opinion, XML is not the best tool for the job. Your structure is very simple and storing in XML would probably double the file size, which is a concern for a mobile device, and would also slow the parsing, also a concern in this case.