可空对象必须具有一个值，Linq to SQL，MVC问题

Question

I've taken over a project for a developer who has left the company and am not overly familiar with MVC. When running the program I get the error that "Nullable object must have a value".

One of the cells in a table is populated by the following:

<td>@SRA_Acquire.Models.Auth.Users.GetUserNameById((int)issue.UserID)</td>

Which is populated by the following:

public static string GetUserNameById(int userId)
{
    return GetUserById(userId).Name;
}

internal static UserProfile GetUserById(int userId)
{
    var db = new UsersContext();
    return db.UserProfiles.Where(c => c.UserId == userId).Single();
}

When stepping through the code the userId is correct, but I get errors stating that c.UserID does not exist in the current context

However in my AccountModels.cs it shows

public class UsersContext : DbContext
{
    public UsersContext()
        : base("AuthContext")
    {
    }

    public DbSet<UserProfile> UserProfiles { get; set; }
    public DbSet<UsersInRoles> UsersInRoles { get; set; }
    public DbSet<Roles> Roles { get; set; }
}

[Table("UserProfile", Schema = "dbo")]
public class UserProfile 
{
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int UserId { get; set; }
    public string UserName { get; set; }
    public string Name { get; set; }
    public string Email { get; set; }
    public bool IsLockedOut { get; set; }
}

What am I missing?

Answer 1

尝试更新c.UserId == userId条件，以便避免此类错误：

c => c.UserId != null && c.UserId == userId