Question

I’m using Entity Framework 4.0. Now I need to restrict access to a table while I’m reading from it or writing to it. Probably that’s about transaction isolation level.

How do I do that?

Update

here is what I have

using (var db = new MyDb())
{
    using (TransactionScope scope = new TransactionScope())
    {
        var item = db.MyItems.Single(x => x.Id == 5);
        item.Price = 12;
        db.SaveChanges();
        scope.Complete(); 
    }
}

However, when I put a breakpoint at any line inside using (TransactionScope scope and when I’m stopping there and then I go to Sql Server Management Studio and doing a select query (or even update!) from a table that is using inside a transaction, I’m not getting an error for some reason. But why? It must not allow me to read a data while a transaction is executing.

Answer 1

By default, a Transaction has an IsolationLevel of Serializable. Serializable is the highest level. It requires that the transaction completes before any other transaction is allowed to operate on the data.

It has the following restrictions:

• Statements cannot read data that has been modified but not yet
  committed by other transactions.
• No other transactions can modify
  data that has been read by the current transaction until the current
  transaction completes.
• Other transactions cannot insert new rows with
  key values that would fall in the range of keys read by any
  statements in the current transaction until the current transaction
  completes.

This is a great blog post that explains how to use Transactions with the Entity Framework: Entity Framework transaction scope examples

UPDATE

In Entity Framework 6 the default IsolationLevel is changed to READ_COMMITTED_SNAPSHOT for databases created using Code First, potentially allowing for more scalability and fewer deadlocks. See the future spec of EF 6