Databases
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    primarykey
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    1. This table or related slice is empty.
    1. POHow to perform duplicate key validation using entlib (or DataAnnotations), MVC, and Repository pattern
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    1. PTAnswer
    1. This table or related slice is empty.
    1. USCraig Stuntz
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    1. This table or related slice is empty.
    1. This table or related slice is empty.
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    1. COI don't understand how doing this in the DB is the only multi-user-safe option. My repositories operate using a UnitOfWork pattern which wraps an ObjectContext with EntityTransaction. I'd like to avoid db-level validation because 1) it makes this requirement less testable, 2) it involves catching a SQLException, and 3) there is no way to invoke the validator from the client without hitting the database.
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      1. USdanludwig
    2. CO@olivehour, only the DB can see outside of its own transaction. A unique constraint on the DB *will not fail, period,* even if the conflicting, committed record is in a transaction not visible to yours. Doing it in the app server means that the following is possible: 1) User A checks for conflicts, finds none, 2) User B checks for conflicts, finds none, 3) User A commits "Bob" as a name, 4) User "B" commits "Bob" as a name. Oops. You don't need to test features built in to your DB server; that's not your code. You *can* validate this from the client, though.
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      1. USCraig Stuntz
    3. COOK, so you're talking about concurrency. I have a timestamp column in the db table, and the app will check the row version before doing any commits (optimistic concurrency implementation). When User B commits "Bob", the timestamp values won't match and the app will know there is a concurrency conflict. I can't put a unique constraint on the column in question, because the DB also has an IsCurrentVersion column. All old rows are kept in the database. So, there can be many users in the DB with the same UserID, but only one will have IsCurrentVersion == true. A trigger would be needed instead.
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      1. USdanludwig
 

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Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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