I'm having a weird one here. I'm doing Microsoft's Razor and EF tutorial and I don't know what's wrong with this code:

public class Student
{
    public int ID { get; set; }
    public string LastName { get; set; }
    public string FirstMidName { get; set; }
    public DateTime EnrollmentDate { get; set; }

    public ICollection<Enrollment> Enrollments { get; set; }
}

//CRUD Create Method
public async Task<IActionResult> OnPostAsync()
{
    var emptyStudent = new Student();

    if (await TryUpdateModelAsync<Student>(
        emptyStudent,
        "Student",
        s => s.FirstMidName,
        s => s.LastName,
        s => s.EnrollmentDate))
    {
        _context.Students.Add(emptyStudent);
        await _context.SaveChangesAsync();
        return RedirectToPage("./Index");
    }

    return Page();
}

The form is as follows:

<form method="post">
    <div asp-validation-summary="ModelOnly" class="text-danger"></div>

    <div class="form-group">
        <label asp-for="Student.LastName" class="control-label"></label>
        <input asp-for="Student.LastName" class="form-control" />
        <span asp-validation-for="Student.LastName" class="text-danger"></span>
    </div>

    <div class="form-group">
        <label asp-for="Student.FirstMidName" class="control-label"></label>
        <input asp-for="Student.FirstMidName" class="form-control" />
        <span asp-validation-for="Student.FirstMidName" class="text-danger"></span>
    </div>

    <div class="form-group">
        <label asp-for="Student.EnrollmentDate" class="control-label"></label>
        <input asp-for="Student.EnrollmentDate" class="form-control" />
        <span asp-validation-for="Student.EnrollmentDate" class="text-danger"></span>
    </div>

    <div class="form-group">
        <input type="submit" value="Create" class="btn btn-primary" />
    </div>
</form>

I have debugged and analyzed the traffic. I do know that I'm receiving the form with the values and actually, by using Request.Form["student.FirstMidName"] and so on, I can populate emptyStudent.

I still don't understand what's wrong, since the code, apparently, is fine. However, TryUpdateModelAsync is returning false.

Any idea why is this happening?

I'm having a weird one here. I'm doing Microsoft's Razor and EF tutorial and I don't know what's wrong with this code:

public class Student
{
    public int ID { get; set; }
    public string LastName { get; set; }
    public string FirstMidName { get; set; }
    public DateTime EnrollmentDate { get; set; }

    public ICollection<Enrollment> Enrollments { get; set; }
}

//CRUD Create Method
public async Task<IActionResult> OnPostAsync()
{
    var emptyStudent = new Student();

    if (await TryUpdateModelAsync<Student>(
        emptyStudent,
        "Student",
        s => s.FirstMidName,
        s => s.LastName,
        s => s.EnrollmentDate))
    {
        _context.Students.Add(emptyStudent);
        await _context.SaveChangesAsync();
        return RedirectToPage("./Index");
    }

    return Page();
}

The form is as follows:

<form method="post">
    <div asp-validation-summary="ModelOnly" class="text-danger"></div>

    <div class="form-group">
        <label asp-for="Student.LastName" class="control-label"></label>
        <input asp-for="Student.LastName" class="form-control" />
        <span asp-validation-for="Student.LastName" class="text-danger"></span>
    </div>

    <div class="form-group">
        <label asp-for="Student.FirstMidName" class="control-label"></label>
        <input asp-for="Student.FirstMidName" class="form-control" />
        <span asp-validation-for="Student.FirstMidName" class="text-danger"></span>
    </div>

    <div class="form-group">
        <label asp-for="Student.EnrollmentDate" class="control-label"></label>
        <input asp-for="Student.EnrollmentDate" class="form-control" />
        <span asp-validation-for="Student.EnrollmentDate" class="text-danger"></span>
    </div>

    <div class="form-group">
        <input type="submit" value="Create" class="btn btn-primary" />
    </div>
</form>

I have debugged and analyzed the traffic. I do know that I'm receiving the form with the values and actually, by using Request.Form["student.FirstMidName"] and so on, I can populate emptyStudent.

I still don't understand what's wrong, since the code, apparently, is fine. However, TryUpdateModelAsync is returning false.

Any idea why is this happening?

• c#
• asp-core
• post
• entity-framework-core
• razor-pages

• Is Student.Id marked as auto-generated on insert? If not, it would need a value to be valid. – pjs Commented 2 days ago
• 2 Check ModelState. There should be errors set after TryUpdateModelAsync runs. ModelState is a property in Controller class. Please update your Answer if this helped or if you need further assistance. – Sebastian Siemens Commented 2 days ago
• 2 For collection navigation properties, always initialize them to avoid possible issues with #null. public ICollection<Enrollment> Enrollments { get; } = []; Never expose a setter as with tracked entities you should also never reset a collection reference. – Steve Py Commented 2 days ago
• @pjs, actually yes. Student.Id is marked for auto-generation :). Thank you – DaniWein Commented yesterday

2 Answers 2

Based on Basheer Jarrah's answer

Nullable context will be enabled by default since 6,you may see this document

TryUpdateModelAsync method will trigger model binding again, and false indicates model-binding failing,you may see this document

include it in the form and params of TryUpdateModelAsync() method.

You should avoid assign complex type value with lambda like: s => s.Enrollments

another option besides set Enrollments property nullable

public ICollection<Enrollment>? Enrollments { get; set; }

is disable the feature, the codes for razor page:

builder.Services.AddRazorPages()
    .AddMvcOptions(x=> x.SuppressImplicitRequiredAttributeForNonNullableReferenceTypes = true);

This issue occurs when the navigation property Enrollments is not nullable. Based on the ASP .NET Core docs for non-nullable types:

The validation system treats non-nullable parameters or bound properties as if they had a [Required(AllowEmptyStrings = true)] attribute.

So, either you make Enrollments collection nullable, or include it in the form and params of TryUpdateModelAsync() method.