如何解决空数据库表上的乐观并发异常错误

Question

Using ASP.NET MVC, Entity Framework to perform CRUD ops on a SQL Server database. I am inserting new information into the connected tables. I have numerous tables I do this operation on, but I've never come across this error before.

When I submit my data to the controller I it traverses through the typical EFF stuff. However, when it hits my db.SaveChanges() line, I get this optimistic concurrency exceptions error, referencing that the data may have changed from the db. In this particular situation there is no data in the table, so it doesn't make sense to me.

I followed the recommendation and read some about it. Implemented one of their fixes, but it doesn't work. Doesn't work because it's seeking GetDatabaseValues() and there are none. Have I missed something silly here? I'm simply taking form values and inserting them into two different tables I've set up.

Here's the controller:

[HttpPost]
public ActionResult SubmitUwSelections(FormCollection form)
{
        var cbRating = form["cabRating"]; // Cab Raing ddl
        var filing = form["fileRqd"]; // filing required ddl
        var ifta = form["cbIfta"]; // IFTA cb
        var lossControl = form["lcRqd"]; // Loss control cb
        var app1 = form["AppInFile"]; //Application app in file cb
        var app2 = form["AppRqd"]; //Application app rqd cb
        var um1 = form["UMInFile"]; //UM in file cb
        var um2 = form["UMRqd"]; // UM rqd cb
        var terror1 = form["terrorInFile"]; // terror in file cb
        var terror2 = form["terrorRqd"]; // terror rqd cb
        var lossRun1 = form["LossRunInFile"];// loss run in file cb
        var lossRun2 = form["LossRunRqd"]; //Loss run rqd cb
        var inspect1 = form["cbVehicleInspectInFile"]; //vehicle inspect in file cb
        var inspect2 = form["cbVehicleInspectRqd"]; // vehicle inspect rqd cb
        var mvr1 = form["cbMvrInFile"]; // mvr in file cb
        var mvr2 = form["cbMvrRqd"]; // mvr rqd cb
        var psComments = form["cifComments"]; //section 2 comment box
        var uniqPolicy = form["UniqPolicy"];
        string c = uniqPolicy.ToString();
        int u = Convert.ToInt32(c);

        // need to form up and create variables for the segmentation part of the insert. 
        // Segmentation pieces. 
        var segYear = form["segYear"]; //seg tab segmentation year
        var tractors = form["tractors"]; //seg tab tractors
        var truck = form["trucks"]; //seg tab trucks
        var su = form["serviceUnits"]; //seg tab service units
        var estMileage = form["estAnnMile"]; // segmentation tab Est-Annual Mileage
        var estRvenue = form["estAnnRev"]; //seg tab est annual revenue
        var radius = form["radius"]; // seg tab radius ddl
        var primaryOp = form["primaryOperation"]; //Seg tab primary operation ddl

        int l, m, n, o, p = 0;
        l = Convert.ToInt32(segYear); //Converts seg year into int
        m = Convert.ToInt32(tractors); //converts seg tractors to int
        n = Convert.ToInt32(truck); //converts seg trucks to int
        o = Convert.ToInt32(su); //converts seg service units to int
        p = Convert.ToInt32(estMileage); //converts seg est ann mileage to int
        decimal revenue = Convert.ToDecimal(estRvenue); //converts seg est revenue to decimal

        using (TruckingDb db  = new TruckingDb())
        {
            // Create dto to insert Form collection items 
            CIF_Record_InsertDTO dto = db.CIF_Record.Find(u); //checking to see if row exists
            CIF_Record_InsertDTO dtoSend = new CIF_Record_InsertDTO();
            CIF_Segmentation_InsertDTO segDto = new CIF_Segmentation_InsertDTO();

            if (dto == null)
            {
                // create UniqPolicy dto
                dtoSend.UniqPolicyId = u;

                // Create user insert dto. 
                string user = Request.LogonUserIdentity.Name.Substring(Request.LogonUserIdentity.Name.LastIndexOf(@"\") + 1);
                dtoSend.Underwriter = user;

                // set the cif record comments section. 
                dtoSend.Comments = psComments;

                // Set the UwSegmentation value
                dtoSend.UwSegmentationSubmit = true;

                // Set segmentation dto's
                segDto.SegmentationYear = l;
                segDto.Tractors = m;
                segDto.Trucks = n;
                segDto.ServiceUnits = o;
                segDto.EstAnnualMileage = p;
                segDto.EstAnnualRevenue = revenue;
                segDto.Radius = radius;
                segDto.PrimaryOperation = primaryOp;

                // 1. inserting dto's into two different tables
                db.CIF_Record.Add(dtoSend);  
                db.CIF_Segmentation.Add(segDto); //2.
            }
            else
            {
                // temporarily empty
            }

            bool saveFailed;

            do
            {
                saveFailed = false;

                try
                {
                    db.SaveChanges();
                }
                catch (DbUpdateConcurrencyException ex)
                {
                    saveFailed = true;

                    //update original values from the db
                    var entry = ex.Entries.Single();
                    entry.OriginalValues.SetValues(entry.GetDatabaseValues());
                }
            } while (saveFailed);
        }

        return RedirectToAction("CompleteCIF");
}    

The do while just above what their first fix, but it doesn't work. Hits the catch and hits the entry.GetDatabaseValues() , but of course there's no OG values to begin with. Why is the saveChanges() not working? Thanks again for the help.

Answer 1

Check that any columns that have automatically generated values in the database are marked in your entity configuration as Identity for key columns, and Computed for everything else. DateTime values may have issues with the SQL type and milliseconds, so check that they are DateTime2(7) may help. Depending on the table structure, an insert can result in an Insert+Update and this could trigger the concurrency exception, which should only occur in Updates or Deletes, not Inserts. When EF encounters a defaulted column it may confuse that as a concurrent update if it's not configured to account for that.

See ( DbUpdateConcurrencyException on insert ) for details on DateTime related insert issues. In their case, ensuring they were set to "None" for DB Generated options was needed.