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C#•3w ago

Creates new object instead of updating it

Hello, guys, I have a very simple MVC WebApp and I faced a problem. So thing is for some reason my edit method creates new instance in database instead of updating given object. From what I can tell issue is within my html form, because if I add input field for Id there it works fine.

40 Replies

Angius•3w ago

Show code My bet's you're sending a whole database entity to the backend, instead of using a DTO And EF interprets the empty ID as your desire to insert a new entity

YourMajestyOP•3w ago

uff hold on discord blames my message for being too long

<form method="post">
    <div class="border p-3 mt-4">
        <div class="row pb-2">
            <h2>Edit a movie</h2>
            <hr>
        </div>
        <div hidden class="mb-3 p-1">
            <label class="p-0">Id</label>
            <input asp-for="Movie.Id" type="number" class="form-control">
        </div>
        <div class="mb-3 p-1">
            <div asp-validation-summary="ModelOnly" class="text-danger"></div>
            <label class="p-0">Category Name</label>
            <input asp-for="Movie.Title" class="form-control">
            <span asp-validation-for="Movie.Title" class="text-danger"></span>
        </div>
        <div class="mb-3 p-1">
            <label class="p-0">Display Order</label>
            <select asp-for="Movie.CategoryId" class="form-control">
                @foreach (var item in Model.Categories)
                {
                    <option value="@item.Id">@item.Name</option>
                }
            </select>
            <span asp-validation-for="Movie.CategoryId" class="text-danger"></span>
        </div>
        <div class="mb-3 p-1">
            <label class="p-0">Display Order</label>
            <input asp-for="Movie.ReleaseDate" type="date" class="form-control">
            <span asp-validation-for="Movie.ReleaseDate" class="text-danger"></span>
        </div>
        <div class="mb-3 p-1">
            <label class="p-0">Display Order</label>
            <input asp-for="Movie.Rating" type="number" class="form-control">
            <span asp-validation-for="Movie.Rating" class="text-danger"></span>
        </div>
        <div class="row">
            <div class="col-6">
                <button type="submit" class="btn btn-light form-control">Submit</button>
            </div>
            <div class="col-6">
                <a asp-controller="Movie" asp-action="Index" class="btn btn-outline-primary form-control">Go back</a>
            </div>
        </div>
    </div>
</form>

<form method="post">
    <div class="border p-3 mt-4">
        <div class="row pb-2">
            <h2>Edit a movie</h2>
            <hr>
        </div>
        <div hidden class="mb-3 p-1">
            <label class="p-0">Id</label>
            <input asp-for="Movie.Id" type="number" class="form-control">
        </div>
        <div class="mb-3 p-1">
            <div asp-validation-summary="ModelOnly" class="text-danger"></div>
            <label class="p-0">Category Name</label>
            <input asp-for="Movie.Title" class="form-control">
            <span asp-validation-for="Movie.Title" class="text-danger"></span>
        </div>
        <div class="mb-3 p-1">
            <label class="p-0">Display Order</label>
            <select asp-for="Movie.CategoryId" class="form-control">
                @foreach (var item in Model.Categories)
                {
                    <option value="@item.Id">@item.Name</option>
                }
            </select>
            <span asp-validation-for="Movie.CategoryId" class="text-danger"></span>
        </div>
        <div class="mb-3 p-1">
            <label class="p-0">Display Order</label>
            <input asp-for="Movie.ReleaseDate" type="date" class="form-control">
            <span asp-validation-for="Movie.ReleaseDate" class="text-danger"></span>
        </div>
        <div class="mb-3 p-1">
            <label class="p-0">Display Order</label>
            <input asp-for="Movie.Rating" type="number" class="form-control">
            <span asp-validation-for="Movie.Rating" class="text-danger"></span>
        </div>
        <div class="row">
            <div class="col-6">
                <button type="submit" class="btn btn-light form-control">Submit</button>
            </div>
            <div class="col-6">
                <a asp-controller="Movie" asp-action="Index" class="btn btn-outline-primary form-control">Go back</a>
            </div>
        </div>
    </div>
</form>

this is my html so if I remove this input field for Id, it will create new object

Angius•3w ago

And the backend code? The controller that handles this form's submission?

YourMajestyOP•3w ago

yea second

public async Task<IActionResult> Edit(MovieCategoryVM movieCategoryVM)
        {

            if (!ModelState.IsValid)
            {
                _movieCategoryVM.Movie = movieCategoryVM.Movie;

                return View(_movieCategoryVM);
            }

            try
            {
                await _movieRepo.Update(movieCategoryVM.Movie);
                TempData["SuccessMessage"] = "Movie created successfully!";

                return RedirectToAction("Index");
            }
            catch
            {
                TempData["ErrorMessage"] = "An error occurred while editing the movie. Please try again.";
                return View(_movieCategoryVM);
            }
        }

public async Task<IActionResult> Edit(MovieCategoryVM movieCategoryVM)
        {

            if (!ModelState.IsValid)
            {
                _movieCategoryVM.Movie = movieCategoryVM.Movie;

                return View(_movieCategoryVM);
            }

            try
            {
                await _movieRepo.Update(movieCategoryVM.Movie);
                TempData["SuccessMessage"] = "Movie created successfully!";

                return RedirectToAction("Index");
            }
            catch
            {
                TempData["ErrorMessage"] = "An error occurred while editing the movie. Please try again.";
                return View(_movieCategoryVM);
            }
        }

Angius•3w ago

I'm gonna guess that Movie is the very same type as your database model for a movie

YourMajestyOP•3w ago

so MovieCategoryVM is class to pass more than 1 model to view and back yes

Angius•3w ago

Use a DTO instead A class that contains only the properties you expect the form to send I don't see you using any other properties of MovieCategoryVM here either, so maybe use just that DTO That form only sends movie data after all

YourMajestyOP•3w ago

I use those on the view itself, it contains list of categories for movies

Angius•3w ago

Cool The data you send on GET does not have to be the same as the data you receive on POST The form will send only those properties, so handle only those properties The controller action that handles the form submission doesn't need to know the entire list of categories

YourMajestyOP•3w ago

ah so, I'd create new class, where I will avoid some props I don't need to file like Id and add object of this class as parameter in Edit method?

Angius•3w ago

Use just this object as a parameter of Edit

YourMajestyOP•3w ago

yes and how can I transfer those properties to my database model? The obvious would be to do like

Movie.Id = MovieDTO.Id;
Movie.Title = MovieDTO.Title;
...
...

Movie.Id = MovieDTO.Id;
Movie.Title = MovieDTO.Title;
...
...

Angius•3w ago

Yep

YourMajestyOP•3w ago

but is there smarter way? :harold:

Angius•3w ago

Or .ExecuteUpdateAsync()

var affectedRows = await _context.Movies
    .Where(m => m.Id == id)
    .ExecuteUpdateAsync(s => s
        .SetProperty(m => m.Name, dto.Name)
        .SetProperty(m => m.ReleaseDate, dto.ReleaseDate)
        .SetProperty(m => m.Budget, dto.Budget));

var affectedRows = await _context.Movies
    .Where(m => m.Id == id)
    .ExecuteUpdateAsync(s => s
        .SetProperty(m => m.Name, dto.Name)
        .SetProperty(m => m.ReleaseDate, dto.ReleaseDate)
        .SetProperty(m => m.Budget, dto.Budget));

YourMajestyOP•3w ago

never used this method, will check what it does thanks a lot! it looks pretty much same, like you need to write every property separately

Angius•3w ago

Yeah

YourMajestyOP•3w ago

ok, thanks again! will try to do it using ExecuteUpdateAsync method

Angius•3w ago

It calls the database just once

YourMajestyOP•3w ago

but hold on haha

Angius•3w ago

While fetch -> update -> save, calls it twice

YourMajestyOP•3w ago

I have another model where it looks pretty much same, both form and controller methods and there it works as intended hope im not asking too much, could u take a look? 🥹

Angius•3w ago

Sure

YourMajestyOP•3w ago

<form method="post">
    <div class="border p-3 mt-4">
        <div class="row pb-2">
            <h2>Edit Category</h2>
            <hr>
        </div>
        <div class="mb-3 p-1">
            <div asp-validation-summary="ModelOnly" class="text-danger"></div>
            <label class="p-0">Category Name</label>
            <input asp-for="Name" class="form-control">
            <span asp-validation-for="Name" class="text-danger"></span>
        </div>
        <div class="mb-3 p-1">
            <label class="p-0">Display Order</label>
            <input asp-for="DisplayOrder" class="form-control">
            <span asp-validation-for="DisplayOrder" class="text-danger"></span>
        </div>
        <div class="row">
            <div class="col-6">
                <button type="submit" class="btn btn-light form-control">Submit</button>
            </div>
            <div class="col-6">
                <a asp-controller="Category" asp-action="Index" class="btn btn-outline-primary form-control">Go back</a>
            </div>
        </div>
    </div>
</form>

<form method="post">
    <div class="border p-3 mt-4">
        <div class="row pb-2">
            <h2>Edit Category</h2>
            <hr>
        </div>
        <div class="mb-3 p-1">
            <div asp-validation-summary="ModelOnly" class="text-danger"></div>
            <label class="p-0">Category Name</label>
            <input asp-for="Name" class="form-control">
            <span asp-validation-for="Name" class="text-danger"></span>
        </div>
        <div class="mb-3 p-1">
            <label class="p-0">Display Order</label>
            <input asp-for="DisplayOrder" class="form-control">
            <span asp-validation-for="DisplayOrder" class="text-danger"></span>
        </div>
        <div class="row">
            <div class="col-6">
                <button type="submit" class="btn btn-light form-control">Submit</button>
            </div>
            <div class="col-6">
                <a asp-controller="Category" asp-action="Index" class="btn btn-outline-primary form-control">Go back</a>
            </div>
        </div>
    </div>
</form>

html

public async Task<IActionResult> Edit(Category category)
    {
        if (!ModelState.IsValid)
        {
            return View(category);
        }

        try
        {
            await _categoryRepo.Update(category);
            TempData["SuccessMessage"] = "Category updated successfully!";

            return RedirectToAction("Index");
        }
        catch
        {
            TempData["ErrorMessage"] = "An error occurred while updating the category. Please try again.";
            return View("Index");
        }
    }

public async Task<IActionResult> Edit(Category category)
    {
        if (!ModelState.IsValid)
        {
            return View(category);
        }

        try
        {
            await _categoryRepo.Update(category);
            TempData["SuccessMessage"] = "Category updated successfully!";

            return RedirectToAction("Index");
        }
        catch
        {
            TempData["ErrorMessage"] = "An error occurred while updating the category. Please try again.";
            return View("Index");
        }
    }

controller but the thing is in this case I am not using any separate class for ViewModel

Angius•3w ago

Ah, I just noticed you're doing repositories, huh Is both repositories' .Update() method the same?

YourMajestyOP•3w ago

im using Category model yes ofc they inherit from same Repo class where those method are defined idk if it is proper way to use Repo Pattern lol

Angius•3w ago

The proper way is to not use the repo pattern :KEKW:

YourMajestyOP•3w ago

yeah heard about that as well 💀 could this be the case?

Angius•3w ago

Not sure tbh Could be, that EF works when it's just the model, and doesn't when it's nested as a property of another

YourMajestyOP•3w ago

well let it be :kekw: I'll try to use DTO, cause I guess it is actually proper way to do it?

Angius•3w ago

ye Database entities should never leave the backend boundary

YourMajestyOP•3w ago

if it works will change both things to DTO and just forget lol I just thought of using custom methods like ToDto on Model and ToModel on DTO, is it something eatable?

Angius•3w ago

Leaving the model anemic and adding ToModel and FromModel on the DTO is more recommended Or creating a whole separate class that has a ToModel method, and some MapToDto extension method on IQueryable<Model> so it can be plugged into your LINQ query Or, as I like to do, an Expression<Func<Model, Dto>> that can be plugged into .Select()

YourMajestyOP•3w ago

Uh I am not really sure about my delegate understanding and how to use them properly, so I think I will try to use separate class with extension methods on IQueryable<Model> Thanks a lot for your advices!

Angius•3w ago

public static Expression<Func<Model, Dto>> ToDto = (model) => new Dto {
    Name = model.Name,
    ...
};

public static Expression<Func<Model, Dto>> ToDto = (model) => new Dto {
    Name = model.Name,
    ...
};

YourMajestyOP•3w ago

:pikawhat: Looks scary

Angius•3w ago

Then you just plug it into .Select()

YourMajestyOP•3w ago

(model) is the method parameter here?

Angius•3w ago

var thing = await _ctx.Things
    .Where(...)
    .Select(WhateverClass.ToDto)
    .FirstOrDefaultAsync();

var thing = await _ctx.Things
    .Where(...)
    .Select(WhateverClass.ToDto)
    .FirstOrDefaultAsync();

ye

YourMajestyOP•3w ago

Looks way more eatable ngl Yea definitely worth giving more practice to delegates, will try to work with this as well

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