如何在Date Entity Framework中回滚事务

Question

I am trying to use the Data Entity Framework to create my Data Access Layer. In the work I have done up to now I have used ADO.Net. I am trying to get my head around how transactions work in EF. I ave read loads but its all confussed me even more than I was before!! I would usually do somethink like (simplified for example):

using (SqlConnection conn = new SqlConnection(_connString))
{
    using (SqlTransaction trans = conn.BeginTransaction())
    {
        try
        {
            using (SqlCommand cmd = new SqlCommand("usp_CreateNewInvoice", conn))
            {
                cmd.Transaction = trans;
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.Add(new SqlParameter("@InvoiceName", Invoice.invoicename));
                 cmd.Parameters.Add(new SqlParameter("@InvoiceAddess", Invoice.invoiceaddress));
                 _invoiceid = Convert.ToInt32(cmd.ExecuteScalar());
            }
            foreach (InvoiceLine inLine in Invoice.Lines)
            {
                using (SqlCommand cmd = new SqlCommand("usp_InsertInvoiceLines", conn))
                {
                    cmd.Transaction = trans;
                    cmd.CommandType = CommandType.StoredProcedure;
                    cmd.Parameters.Add(new SqlParameter("@InvNo", _invoiceid));
                    cmd.Parameters.Add(new SqlParameter("@InvLineQty", inLine.lineqty));
                    cmd.Parameters.Add(new SqlParameter("@InvLineGrossPrice", inLine.linegrossprice));
                    cmd.ExecuteNonQuery();
                }
            }
            trans.Commit();
        }
        catch (SqlException sqlError)
        {
            trans.Rollback();
        }
    }
}

Now I want to do the same in EF:

        using (TransactionScope scope = new TransactionScope())
        {
            try
            {
                var DbContext = new CCTStoreEntities();

                CCTInvoice invHead = new CCTInvoice();
                invHead.Name = Invoice.invoicename;
                invHead.Address = Invoice.invoiceaddress;

                DbContext.CCTInvoices.Add(invHead);
                DbContext.SaveChanges(false);
                _iid = invHead.InvoiceId;

                foreach (InvoiceLine inLine in Invoice.Lines)
                {
                    CCTInvoiceLine invLine = new CCTInvoiceLine();
                    invLine.InvoiceNo = _iid;
                    invLine.Quantity = inLine.lineqty;
                    invLine.GrossPrice = inLine.linegrossprice;
                    DbContext.CCTInvoiceLines.Add(invHead);
                    DbContext.SaveChanges(false);
                }

                DbContext.SaveChanges();
                scope.Complete();

            }
            catch
            {
                //Something went wrong
                //Rollback!
            }
        }

From what I read SaveChanges(false) means the changes being made will continue to be tracked. But how do I rollback the transaction if something goes wrong?

Answer 1

The rollback mechanism in a TransactionScope is implicit.

Basically, if you don't call Complete before the TransactionScope gets disposed it will automatically rollback. See the Rolling back a transaction section in Implementing an Implicit Transaction using Transaction Scope .

So technically, you don't even need to use a try...catch here (unless you want to perform some other action like logging).

Answer 2

You don't need to do anything on your catch block. Just by not calling DbContext.SaveChanges no changes will be sent to the database, and they will be lost once DbContext is disposed.

You do have a problem though. DbContext must be wrapped on a using block as follows to be properly disposed. BTW, I don't think DbContext.SaveChanges(false); is needed, your code should work with just the final DbContext.SaveChanges(); . EF will take care of wiring up all your Foreign Keys, so you don't need to do that explicitly.

    using (TransactionScope scope = new TransactionScope())
    {
        try
        {
            using (var DbContext = new CCTStoreEntities())
            {
                CCTInvoice invHead = new CCTInvoice();
                invHead.Name = Invoice.invoicename;
                invHead.Address = Invoice.invoiceaddress;

                DbContext.CCTInvoices.Add(invHead);
                DbContext.SaveChanges(false); // This is not needed
                _iid = invHead.InvoiceId;     // This is not needed

                foreach (InvoiceLine inLine in Invoice.Lines)
                {
                    CCTInvoiceLine invLine = new CCTInvoiceLine();
                    invLine.InvoiceNo = _iid; // This is not needed
                    invLine.Quantity = inLine.lineqty;
                    invLine.GrossPrice = inLine.linegrossprice;
                    DbContext.CCTInvoiceLines.Add(invHead);
                    DbContext.SaveChanges(false); // This is not needed
                }

                DbContext.SaveChanges();
                scope.Complete();
            }
        }
        catch
        {
            //Something went wrong
            //Rollback!
        }
    }