Questions

How can we do pessimistic locking in Entity Framework?

entity framework 6 and pessimistic concurrency

  1. Creation a transactionScope around my DbContext with serialised isolation level.
  2. Create a DbContext.
  3. Do some reads.
  4. Do some changes to objects.
  5. Call SaveChanges on the DbContext.
  6. Commit the transaction scope (thus saving the changes)

How does Entity Framework handle concurrency?

The general approach to handle a concurrency conflicts is:

  1. Catch DbUpdateConcurrencyException during SaveChanges .
  2. Use DbUpdateConcurrencyException.
  3. Refresh the original values of the concurrency token to reflect the current values in the database.
  4. Retry the process until no conflicts occur.

How do I enable concurrency mode in Entity Framework?

If you do want to implement this approach to concurrency, you have to mark all non-primary-key properties in the entity you want to track concurrency for by adding the ConcurrencyCheck attribute to them. That change enables the Entity Framework to include all columns in the SQL WHERE clause of UPDATE statements.

What is optimistic concurrency in Entity Framework?

An optimistic concurrency assumes that there would not be concurrent updates, so it allows multiple processes or users to read and update the data. But in case concurrent updates happen, then it uses concurrency tokens to identify if the version from the update is matching with version from the database.

Could you explain pessimistic locking in Entity Framework?

You asked about Pessimistic Concurrency . The answer is: it is not supported yet in Entity Framework. In other words, by conventional API of EF you cannot lock a table or some rows for SELECT like what for example Oracle does via SELECT FOR UPDATE .

What is pessimistic concurrency?

Pessimistic concurrency involves locking rows at the data source to prevent other users from modifying data in a way that affects the current user.

How do you handle concurrency issues?

Possible Solutions

  1. Ignore It. The simplest technique is to just ignore it, hoping it will never happen; or if it does happen, that there won’t be a terrible outcome.
  2. Locking. Another popular technique for preventing lost update problems is to use locking techniques.
  3. Read Before Write.
  4. Timestamping.

What is optimistic locking and pessimistic locking?

Optimistic locking , where a record is locked only when changes are committed to the database. Pessimistic locking , where a record is locked while it is edited.

How do you deal with optimistic concurrency?

Optimistic concurrency involves optimistically attempting to save your entity to the database in the hope that the data there has not changed since the entity was loaded. If it turns out that the data has changed then an exception is thrown and you must resolve the conflict before attempting to save again.

What is the difference between pessimistic locking and optimistic locking?

There are two models for locking data in a database: Optimistic locking , where a record is locked only when changes are committed to the database. Pessimistic locking , where a record is locked while it is edited.

What is the difference between optimistic and pessimistic?

To be optimistic about a situation is to expect it to turn out in a good way. If you’re generally optimistic, you’re an optimist—you tend to look at things favorably. Pessimistic means the opposite: expecting a situation to turn out in a bad way or being a pessimist—always expecting the worst.

What is the difference between optimistic and pessimistic concurrency?

Optimistic concurrency control is based on the idea of conflicts and transaction restart while pessimistic concurrency control uses locking as the basic serialization mechanism. Analytic and simulation models of both mechanisms were developed in order to compare them as far as transaction response time is concerned.

This is called pessimistic concurrency. For example, before you read a row from a database, you request a lock for read-only or for update access. If you lock a row for update access, no other users are allowed to lock the row either for read-only or update access, because they would get a copy of data that’s in the process of being changed.

The Entity Framework provides no built-in support for it, and this tutorial doesn’t show you how to implement it. The alternative to pessimistic concurrency is optimistic concurrency. Optimistic concurrency means allowing concurrency conflicts to happen, and then reacting appropriately if they do.

How does the Entity Framework handle concurrency conflicts?

When the Entity Framework finds that no rows have been updated by the Update or Delete command (that is, when the number of affected rows is zero), it interprets that as a concurrency conflict. Configure the Entity Framework to include the original values of every column in the table in the Where clause of Update and Delete commands.

Should I worry about concurrency in my application?

In many applications, this risk is acceptable: if there are few users, or few updates, or if isn’t really critical if some changes are overwritten, the cost of programming for concurrency might outweigh the benefit. In that case, you don’t have to configure the application to handle concurrency conflicts.