I need to provide AutocompleteBox that will give user ability to input data. Completion should be provided for string field(for example: UserName). The issue is that source DB table consist of hundred of thousands records with 10 fields.
How can I handle this in Silverlight?
First, keep your service payload as small as possible. The AutoCompleteBox should only need one or two fields - a key and value pair - so that when they select the item, your application can then make another query to fetch the rest of the data for that particular record.
Second, I recommend paging your auto-complete results. Don't make the initial query until the user has entered two or three characters into the AutoCompleteBox. Once they do, query the database to get a subset of values that closer match their criteria. If they remove characters, you will need to re-query the table to change the data source values.
The key is to 1) index your table based on the string values and 2) bring back as little as possible from the server to the client so that you keep your network payload small.