Question

我已经通过IdentityUser类扩展了ApplicationUser，该类具有几个自定义字段，以匹配我在SQL Server DB中拥有的AspNetUsers表。其中有两个在SQL中定义为，例如：MyDate datetime2 null。在我的ApplicationUser类中，它将是：datetime? MyDate;。

现在，我可以将其设置为null的唯一方法是使用与Entity Framework分开的T-SQL命令，如果为null，则我的应用程序会引发从数据库读取它的异常。

我确实承认，在我对其进行更新以匹配数据库之前，它在datetime MyDate中被错误地声明为ApplicationUser。这是我看到的问题的原因吗？如果是这样，如何获取我的ApplicationUser来匹配当前的数据库架构？

例外：

01/10/19 17:14:47.034 ERROR 114 MyApp.Global - Exception occurred: 
System.Web.HttpUnhandledException (0x80004005): Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.Data.ConstraintException: The 'MyDateUtc' property on 'ApplicationUser' could not be set to a 'null' value. You must set this property to a non-null value of type 'System.DateTime'. 
   at System.Data.Entity.Core.Common.Internal.Materialization.Shaper.ErrorHandlingValueReader`1.GetValue(DbDataReader reader, Int32 ordinal)
   at lambda_method(Closure , Shaper )
   at System.Data.Entity.Core.Common.Internal.Materialization.Shaper.HandleEntityAppendOnly[TEntity](Func`2 constructEntityDelegate, EntityKey entityKey, EntitySet entitySet)
   at lambda_method(Closure , Shaper )
   at System.Data.Entity.Core.Common.Internal.Materialization.Coordinator`1.ReadNextElement(Shaper shaper)
   at System.Data.Entity.Core.Common.Internal.Materialization.Shaper`1.SimpleEnumerator.<MoveNextAsync>d__4.MoveNext()

这里是ApplicationUser类（略有修饰）和支持类：

public class ApplicationUser : IdentityUser<long, CustomUserLogin, CustomUserRole, CustomUserClaim>
{
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.None)]
    public override long Id
    {
        get { return base.Id; }
        set { base.Id = value; }
    }

    public DateTime? MyDateUtc { get; set; }

    public ClaimsIdentity GenerateUserIdentity(UserManager<ApplicationUser, long> manager)
    {
        // Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType
        var userIdentity = manager.CreateIdentity(this, DefaultAuthenticationTypes.ApplicationCookie);
        // Add custom user claims here
        return userIdentity;
    }

    public Task<ClaimsIdentity> GenerateUserIdentityAsync(ApplicationUserManager manager)
    {
        return Task.FromResult(GenerateUserIdentity(manager));
    }
}

public class ApplicationDbContext : IdentityDbContext<ApplicationUser, CustomRole, long, CustomUserLogin, CustomUserRole, CustomUserClaim>
{
    public ApplicationDbContext() : base("MyDbConnection")
    {
    }

    public static ApplicationDbContext Create()
    {
        return new ApplicationDbContext();
    }
}

public class CustomUserRole : IdentityUserRole<long> { }
public class CustomUserClaim : IdentityUserClaim<long> { }
public class CustomUserLogin : IdentityUserLogin<long> { }

public class CustomRole : IdentityRole<long, CustomUserRole>
{
    public CustomRole() { }
    public CustomRole(string name) { Name = name; }
}

public class CustomUserStore : UserStore<ApplicationUser, CustomRole, long, CustomUserLogin, CustomUserRole, CustomUserClaim>
{
    public CustomUserStore(ApplicationDbContext context) : base(context)
    {
    }
}

public class CustomRoleStore : RoleStore<CustomRole, long, CustomUserRole>
{
    public CustomRoleStore(ApplicationDbContext context) : base(context)
    {
    }
}

Answer 1

DateTime是Struct，因此是value type。这意味着不能将其设置为null。

您可以在可为空的运算符的帮助下解决您的问题。在类型之后使用问号（？）或使用通用样式Nullable。

Nullable <DateTime> MyDateUtc;

或

DateTime? MyDateUtc;

您应该检查您的DbContext班级，以防万一您需要设置班级的属性。更多信息here

身份日期时间？字段不允许为空

1 个答案: