带有非空值的“无法将值NULL插入列”

Question

This is the code I have:

Controller action method:

[HttpPost]
public ActionResult Create(Goal goal)
{
    if (ModelState.IsValid)
    {
        repository.SaveGoal(goal);
        return View("Index");
    }
    else
    {
        return View(goal);
    }
}

Model:

public class Goal
{
    [Required]
    public int GoalId { get; set; }

    [Required]
    public string Name { get; set; }

    [Required]
    [HiddenInput(DisplayValue = false)]
    public decimal Latitude { get; set; }

    [Required]
    [HiddenInput(DisplayValue = false)]
    public decimal Longitude { get; set; }

    [Required]
    public bool IsPrivate { get; set; }
}

Repository:

public class EFGoalRepository : IGoalRepository
{
    private EFDbContext context = new EFDbContext();

    public IQueryable<Goal> Goals
    {
        get { return context.Goals; }
    }

    public void SaveGoal(Goal goal)
    {
        context.Goals.Add(goal);
        context.SaveChanges(); // the line which causes the exception
    }
}

The problem: When I try to save a new Goal object with GoalId set to 0 , I get the following error:

Cannot insert the value NULL into column 'GoalId', table 'TravelGoals.dbo.Goals'; column does not allow nulls. INSERT fails. The statement has been terminated.

I'm still new at ASP.NET MVC, but I believe this worked when I tried it a month ago with a different project.

All the values in my Goal object are valid (non- null , Name is of correct length). The GoalId property is set to 0 , so it is not null either. I thought that Entity Framework would automatically assign a value to it.

What can I do to make this work?

Answer 1

What I needed to do was setting the column as identity in SQL Server.

Probably the simplest way to do this (assuming you're using Visual Studio):

• Open the SQL Server Object Explorer
• Double-click the table you want to edit (or right-click and select View Designer)
• Open the Properties window
• Select the column in the Identity Column property as shown below

Answer 2

Problem is GoalId is not identity.Put this attribut on GoalId

[Key]
public int GoalId { get; set; }

If your EF version is lower than 5 use this:

[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int GoalId { get; set; }