C#•6mo ago

The value '' is invalid. for primary key in MVC

I'm practicing MVC with asp.net and building a simple todo app. I have my Model:

    public class Todo
    {
        public int Id { get; set; }
 
        public string? Name { get; set; }
    }
}

    public class Todo
    {
        public int Id { get; set; }
 
        public string? Name { get; set; }
    }
}

and MVC controller:

        public IActionResult Insert()
        {
            return View("_Form");
        }
        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Insert([Bind("Id, Name")]Todo todo)
        {
            if (ModelState.IsValid)
            {
                _context.Add(todo);
                await _context.SaveChangesAsync();
                return RedirectToAction(nameof(Index));
            }
            return View("_Form",todo);
        }

        public IActionResult Insert()
        {
            return View("_Form");
        }
        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Insert([Bind("Id, Name")]Todo todo)
        {
            if (ModelState.IsValid)
            {
                _context.Add(todo);
                await _context.SaveChangesAsync();
                return RedirectToAction(nameof(Index));
            }
            return View("_Form",todo);
        }

and my view _Form.cshtml:

@model Todo
<form asp-action="Insert" id="form-action" method="post" role="form">
    <div asp-validation-summary="All"></div>
    <label asp-for="Name"></label>
    <input asp-for="Id" type="hidden" />
    <input asp-for="Name" />
    <span asp-validation-for="Name"></span>
    <input type="submit" id ="form-button" value="Add Todo" />
</form>

@model Todo
<form asp-action="Insert" id="form-action" method="post" role="form">
    <div asp-validation-summary="All"></div>
    <label asp-for="Name"></label>
    <input asp-for="Id" type="hidden" />
    <input asp-for="Name" />
    <span asp-validation-for="Name"></span>
    <input type="submit" id ="form-button" value="Add Todo" />
</form>

When I try to run the program, the data is not written into my database and I also get the error The value '' is invalid , when I run the program in debug, the error cause from Id value, from what I found on the internet, people that had this error only cause with other attribute, but not primary key as mine. So I'm frustrated right now, because it's primary key, so I cannot just make it nullable or assign a default value as the normal attribute.

15 Replies

yatta•6mo ago

For the primary in my database, I believe it has all the standards of a primary key

Angius•6mo ago

You're adding a new todo with the primary key already defined instead of letting the database generate that key Perhaps there's some conflict, like trying to insert an item with ID that already exists

yatta•6mo ago

not likely, because there's no record ever inserted into my database, but I think it might has something to do with the id value when my method get is 0 when I try to run it ?

Angius•6mo ago

Could be I don't think 0 is a valid PK Again, it would be best if you just let the database generate them

yatta•6mo ago

how could I do that from my method? Excluding the id binding ?

x0rld•6mo ago

you could create a custom dto for that cause the id isn't useful in your form

Angius•6mo ago

First of all, don't pass the database model around and use a DTO

yatta•6mo ago

could you give me more detail ? I dont think I understand you entirely Arrestbi

Angius•6mo ago

public record TodoDto(string Name);

        public IActionResult Insert()
        {
            return View("_Form");
        }
        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Insert([FromForm]TodoDto data)
        {
            if (ModelState.IsValid)
            {
                var todo = new Todo {
                    Name = data.Name,
                };
                _context.Add(todo);
                await _context.SaveChangesAsync();
                return RedirectToAction(nameof(Index));
            }
            return View("_Form",todo);
        }

public record TodoDto(string Name);

        public IActionResult Insert()
        {
            return View("_Form");
        }
        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Insert([FromForm]TodoDto data)
        {
            if (ModelState.IsValid)
            {
                var todo = new Todo {
                    Name = data.Name,
                };
                _context.Add(todo);
                await _context.SaveChangesAsync();
                return RedirectToAction(nameof(Index));
            }
            return View("_Form",todo);
        }

@model TodoDto
<form asp-action="Insert" id="form-action" method="post" role="form">
    <div asp-validation-summary="All"></div>
    <label asp-for="Name"></label>
    <input asp-for="Name" />
    <span asp-validation-for="Name"></span>
    <input type="submit" id ="form-button" value="Add Todo" />
</form>

@model TodoDto
<form asp-action="Insert" id="form-action" method="post" role="form">
    <div asp-validation-summary="All"></div>
    <label asp-for="Name"></label>
    <input asp-for="Name" />
    <span asp-validation-for="Name"></span>
    <input type="submit" id ="form-button" value="Add Todo" />
</form>

x0rld•6mo ago

I'm not even sure you need the FromForm these day 🤔

yatta•6mo ago

we dont need [HttpPost] and [ValidateAntiForgeryToken] anymore ?

Angius•6mo ago

I didn't remove them

yatta•6mo ago

oh wait, mb I was Arrestbi

code actually works, ty a lot, I'll try to see the different and learn thumbbi

Angius•6mo ago

+public record TodoDto(string Name);

        public IActionResult Insert()
        {
            return View("_Form");
        }
        [HttpPost]
        [ValidateAntiForgeryToken]
-        public async Task<IActionResult> Insert([Bind("Id, Name")]Todo todo)
+        public async Task<IActionResult> Insert([FromForm]TodoDto data)
        {
            if (ModelState.IsValid)
            {
+               var todo = new Todo {
+                   Name = data.Name,
+               };
                _context.Add(todo);
                await _context.SaveChangesAsync();
                return RedirectToAction(nameof(Index));
            }
            return View("_Form",todo);
        }

+public record TodoDto(string Name);

        public IActionResult Insert()
        {
            return View("_Form");
        }
        [HttpPost]
        [ValidateAntiForgeryToken]
-        public async Task<IActionResult> Insert([Bind("Id, Name")]Todo todo)
+        public async Task<IActionResult> Insert([FromForm]TodoDto data)
        {
            if (ModelState.IsValid)
            {
+               var todo = new Todo {
+                   Name = data.Name,
+               };
                _context.Add(todo);
                await _context.SaveChangesAsync();
                return RedirectToAction(nameof(Index));
            }
            return View("_Form",todo);
        }

-@model Todo
+@model TodoDto
 <form asp-action="Insert" id="form-action" method="post" role="form">
     <div asp-validation-summary="All"></div>
     <label asp-for="Name"></label>
-    <input asp-for="Id" type="hidden" />
     <input asp-for="Name" />
     <span asp-validation-for="Name"></span>
     <input type="submit" id ="form-button" value="Add Todo" />
 </form>

-@model Todo
+@model TodoDto
 <form asp-action="Insert" id="form-action" method="post" role="form">
     <div asp-validation-summary="All"></div>
     <label asp-for="Name"></label>
-    <input asp-for="Id" type="hidden" />
     <input asp-for="Name" />
     <span asp-validation-for="Name"></span>
     <input type="submit" id ="form-button" value="Add Todo" />
 </form>

x0rld•6mo ago

https://martinfowler.com/eaaCatalog/dataTransferObject.html

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The value '' is invalid. for primary key in MVC