ASP.NET 核心嵌入对象和并发异常

Question

I am studying asp.net core using this project: https://docs.microsoft.com/en-us/aspnet/core/data/ef-rp/read-related-data?view=aspnetcore-3.0&tabs=visual-studio#create-instructor-pages

I would like to add concurrency exceptions for the Instructor object, the object contains another object OfficeAssignment. https://docs.microsoft.com/en-us/aspnet/core/data/ef-rp/complex-data-model?view=aspnetcore-3.0&tabs=visual-studio

I added [Timestamp] property RowVersion for both objects. I have it working for the InstructorObject but changes to the OfficeAssignment Location property go undetected.

Below is the update code used for the postback

 public async Task<IActionResult> OnPostAsync(int id, int[] selectedCourses)
        {
            var instructor = await _context.Instructors
                .Include(i => i.OfficeAssignment)
                .Include(i => i.CourseAssignments).ThenInclude(ca => ca.Course)
                .FirstOrDefaultAsync(i => i.Id == id);

            var officeAssignment = await _context.OfficeAssignments
                .FirstOrDefaultAsync(oa => oa.InstructorId == instructor.Id);

            if (instructor == null)
            {
                return HandleNotFound(instructor);
            }
            _context.Entry(instructor).Property("RowVersion").OriginalValue = Instructor.RowVersion;
            _context.Entry(officeAssignment).Property("RowVersion").OriginalValue = Instructor.OfficeAssignment.RowVersion;

            if (await TryUpdateModelAsync<Instructor>(
                instructor,
                "Instructor",
                i => i.LastName, i => i.FirstMidName, i => i.HireDate, i => i.OfficeAssignment))
            {
                try
                {
                    UpdateInstructorCourses(_context, selectedCourses, instructor);
                    await _context.SaveChangesAsync();
                    return RedirectToPage("./Index");
                }
                catch (DbUpdateConcurrencyException ex)
                {
                    foreach (var exceptionEntry in ex.Entries)
                    {
                        if (exceptionEntry.Entity is Instructor)
                        {
                            var exceptionEntity = (Instructor)exceptionEntry.Entity;
                            var databaseValues = await exceptionEntry.GetDatabaseValuesAsync();
                            if (databaseValues == null)
                            {
                                return HandleNotFound(instructor);
                            }

                            var databaseEntity = (Instructor)databaseValues.ToObject();
                            SetErrorMessage(exceptionEntity, databaseEntity);

                            Instructor.RowVersion = databaseEntity.RowVersion;
                            ModelState.Remove("Instructor.RowVersion");
                        }
                        else if (exceptionEntry.Entity is OfficeAssignment)
                        {
                            var exceptionEntity = (OfficeAssignment)exceptionEntry.Entity;
                            var databaseValues = exceptionEntry.GetDatabaseValues();
                            if (databaseValues == null)
                            {
                                return HandleNotFound(instructor);
                            }

                            var databaseEntity = (OfficeAssignment)databaseValues.ToObject();
                            SetErrorMessage(exceptionEntity, databaseEntity);

                            Instructor.OfficeAssignment.RowVersion = databaseEntity.RowVersion;
                            ModelState.Remove("Instructor.OfficeAssignment.RowVersion");
                        }
                    }
                }
            }

            PopulateAssignedCourseData(_context, instructor);
            return Page();
        }

Answer 1

RowVersion is a tracking property, you need to remove the AsNoTracking() for your officeAssignment .

Besides,since you have set RowVersion for both models that you also need to put that original RowVersion property value in the OriginalValues collection for the entity.

1.Add below code on Page:

<input type="hidden" asp-for="Instructor.OfficeAssignment.RowVersion" />

Sample demo:

<div class="row">
<div class="col-md-4">
    <form method="post">
        <div asp-validation-summary="ModelOnly" class="text-danger"></div>
        <input type="hidden" asp-for="Instructor.ID" />
        <input type="hidden" asp-for="Instructor.RowVersion" />
        <div class="form-group">
            <label asp-for="Instructor.LastName" class="control-label"></label>
            <input asp-for="Instructor.LastName" class="form-control" />
            <span asp-validation-for="Instructor.LastName" class="text-danger"></span>
        </div>
        <div class="form-group">
            <label asp-for="Instructor.FirstMidName" class="control-label"></label>
            <input asp-for="Instructor.FirstMidName" class="form-control" />
            <span asp-validation-for="Instructor.FirstMidName" class="text-danger"></span>
        </div>
        <div class="form-group">
            <label asp-for="Instructor.HireDate" class="control-label"></label>
            <input asp-for="Instructor.HireDate" class="form-control" />
            <span asp-validation-for="Instructor.HireDate" class="text-danger"></span>
        </div>
        <input type="hidden" asp-for="Instructor.OfficeAssignment.InstructorID" />
        <input type="hidden" asp-for="Instructor.OfficeAssignment.RowVersion" />
        <div class="form-group">
            <label asp-for="Instructor.OfficeAssignment.Location" class="control-label"></label>
            <input asp-for="Instructor.OfficeAssignment.Location" class="form-control" />
            <span asp-validation-for="Instructor.OfficeAssignment.Location" class="text-danger"></span>
        </div>
        <div class="form-group">
            <input type="submit" value="Save" class="btn btn-primary" />
        </div>
    </form>
</div>

2.POST handler:

public async Task<IActionResult> OnPostAsync(int? id)
    {
        if (!ModelState.IsValid)
        {
            return Page();
        }

        var instructor = await _context.Instructors
            .Include(i => i.OfficeAssignment)
            .FirstOrDefaultAsync(i => i.ID == id);

        //modified code shown below
        var officeAssignment = await _context.OfficeAssignments
            .FirstOrDefaultAsync(oa => oa.InstructorID == instructor.ID);

        _context.Entry(instructor).Property("RowVersion").OriginalValue = Instructor.RowVersion;
        _context.Entry(officeAssignment).Property("RowVersion").OriginalValue = Instructor.OfficeAssignment.RowVersion;

        if (await TryUpdateModelAsync<Instructor>(

            instructor,

            "Instructor",

            i => i.FirstMidName, i => i.LastName,

            i => i.HireDate, i => i.OfficeAssignment))

        {
            try
            {
                UpdateInstructorCourses(_context, selectedCourses, instructor);
                await _context.SaveChangesAsync();
                return RedirectToPage("./Index");
            }
            catch (DbUpdateConcurrencyException ex)
            {
                var exceptionEntry = ex.Entries.Single();

                if (exceptionEntry.Entity.GetType() == typeof(OfficeAssignment))
                {
                    //configure error for OfficeAssignment type
                    throw;
                }
                else
                {
                    //configure error for Instructor type
                    var exceptionEntity = (Instructor)exceptionEntry.Entity;
                    var databaseValues = await exceptionEntry.GetDatabaseValuesAsync();
                    if (databaseValues == null)
                    {
                        return HandleNotFound(instructor);
                    }

                    var databaseEntity = (Instructor)databaseValues.ToObject();
                    databaseEntity.OfficeAssignment = officeAssignment;
                    SetErorMessage(exceptionEntity, databaseEntity);

                    Instructor.RowVersion = databaseEntity.RowVersion;
                    ModelState.Remove("Instructor.RowVersion");
                }
            }


        }

        PopulateAssignedCourseData(_context, instructor);
        return Page();

    }