Entity Framework: Using transactions and rollbacks… Possible?

Question

Issue: (With Sql 2005)

• How can I query the database while the transaction is up? (Since it locks the table)
• How can cause a t

Answer 1

I have been able to solve very similar problem using this code fragment:

var connection = new EntityConnection("name=MyEntities");
connection.Open();
var tran = connection.BeginTransaction(System.Data.IsolationLevel.ReadUncommitted);

try
{
    var dataContext = new MyEntities(connection);

    //CRUD operation1

    //CRUD operation2

    //CRUD operation3 ...

    Assert.AreEqual(expected, actual);
}
catch
{
    throw;
}
finally
{
    tran.Rollback();
    connection.Close();
}

Where MyEntities is the EF DataModel. The crucial part is the setting of the transaction: System.Data.IsolationLevel.ReadUncommitted.
Using this isolation level SQL queries can read you changes done inside the transaction. Also you need to explicitly create a connection as I do on the first and second line. I couldn't make it work using TransactionScope unfortunately.

Answer 2

From MSDN;

"SaveChanges operates within a transaction. SaveChanges will roll back that transaction and throw an exception if any of the dirty ObjectStateEntry objects cannot be persisted. "

So it seems that there is no need to to explicitly add your own transaction handling through TransactionScope.

Answer 3

In my case I delete all records from a Table through plain SQL since EF doesn't provide a functionality for this. After that I add some new entities - but when it fails, the table shouldn't be empty. The use of MSDTC (TransactionScope) seems not possible for me. I reduced the transaction to the DB:

My code:

using (var transaction = context.Connection.BeginTransaction())
{
      // delete all
      base.DeleteAll<TESTEntity>(context);

      // add all
      foreach (var item in items)
      {
           context.TESTEntity.AddObject(item);
      }

      try
      {
           context.SaveChanges();
           transaction.Commit();
           return true;
      }
      catch (Exception ex)
      {
           Logger.Write("Error in Save: " + ex, "Error");
           transaction.Rollback();
           return false;
      }
}

And here the helper functions

    protected void DeleteAll<TEntity>(ObjectContext context) where TEntity : class
    {
        string tableName = GetTableName<TEntity>(context);
        int rc = context.ExecuteStoreCommand(string.Format(CultureInfo.InvariantCulture, "DELETE FROM {0}", tableName));
    }

    protected string GetTableName<TEntity>(ObjectContext context) where TEntity : class
    {
        string snippet = "FROM [dbo].[";

        string sql = context.CreateObjectSet<TEntity>().ToTraceString();
        string sqlFirstPart = sql.Substring(sql.IndexOf(snippet) + snippet.Length);
        string tableName = sqlFirstPart.Substring(0, sqlFirstPart.IndexOf("]"));
        return tableName;
    }