那些遇到过的问题

NullReferenceException:在ef7中添加DateTime列后,对象引用未设置为对象的实例

Gan*_*esh -1 asp.net entity-framework-core

我是asp.net mvc ef 7的新手,试图从vb.net迁移.

我有一个课程如下

[Table("MatGrp")]
public class MatGrp
{
    [Key]
    public decimal Grp_RNo { get; set; }

    [Required]
    [MaxLength(30)]
    [Display(Name = "Group Code")]
    public string Grp_Code { get; set; }

    [Required]
    [MaxLength(100)]
    [Display(Name = "Group Name")]
    public string Grp_Name { get; set; }
    public decimal Cre_By { get; set; }
    public DateTime Cre_DtTm { get; set; }
    public decimal Mod_By { get; set; }
    [DataType(DataType.DateTime)]
    public System.DateTime Mod_DtTm { get; set; }

}
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我为这个类生成了一个控制器,如果我删除公共System.DateTime Mod_DtTm {get; 组; 来自该类的列,但添加此列会在此堆栈跟踪中显示错误

处理请求时发生未处理的异常.

NullReferenceException:未将对象引用设置为对象的实例.

lambda_method(Closure,ValueBuffer)

NullReferenceException:未将对象引用设置为对象的实例.

lambda_method(Closure,ValueBuffer)

Microsoft.Data.Entity.Query.EntityLoadInfo.Materialize()

Microsoft.Data.Entity.Query.Internal.QueryBuffer.GetEntity(IKeyValue keyValue,EntityLoadInfo entityLoadInfo,Boolean queryStateManager)

Microsoft.Data.Entity.Query.ExpressionVisitors.RelationalEntityQueryableExpressionVisitor.CreateEntity [TEntity](IQuerySource querySource,ValueBuffer valueBuffer,Int32 valueBufferOffset,QueryContext queryContext,IEntityType entityType,Boolean trackingQuery,KeyValueFactory keyValueFactory,Func`2 materializer,Boolean allowNullResult,Boolean useQueryBuffer)

lambda_method(Closure,ValueBuffer)

System.Linq.Enumerable.<> c__DisplayClass7_0`3.b__0(TSource x)

System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()

Microsoft.Data.Entity.Query.Internal.LinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.MoveNext()

System.Collections.Generic.List 1..ctor(IEnumerable1个集合)

System.Linq.Enumerable.ToList [TSource](IEnumerable`1 source)

MatGrpsController.cs中的FMWeb.Controllers.MatGrpsController.Index()

  1. return View(_context.MatGrp.ToList());

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

Microsoft.AspNet.Mvc.Controllers.ControllerActionExecutor.ExecuteAsync(MethodInfo的actionMethodInfo,Object实例,对象[] orderedActionArguments)

Microsoft.AspNet.Mvc.Controllers.ControllerActionInvoker.d__6.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(任务任务)

System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()

Microsoft.AspNet.Mvc.Controllers.FilterActionInvoker.d__53.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

Microsoft.AspNet.Mvc.Controllers.FilterActionInvoker.d__44.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.GetResult()

Microsoft.AspNet.Mvc.Infrastructure.MvcRouteHandler.d__6.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.GetResult()

Microsoft.AspNet.Routing.Template.TemplateRoute.d__27.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.GetResult()

Microsoft.AspNet.Routing.RouteCollection.d__9.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.GetResult()

Microsoft.AspNet.Builder.RouterMiddleware.d__4.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.GetResult()

Microsoft.AspNet.Authentication.AuthenticationMiddleware`1.d__18.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

Microsoft.AspNet.Authentication.AuthenticationMiddleware`1.d__18.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.GetResult()

Microsoft.AspNet.Authentication.AuthenticationMiddleware`1.d__18.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

Microsoft.AspNet.Authentication.AuthenticationMiddleware`1.d__18.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.GetResult()

Microsoft.AspNet.Authentication.AuthenticationMiddleware`1.d__18.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

Microsoft.AspNet.Authentication.AuthenticationMiddleware`1.d__18.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.GetResult()

Microsoft.AspNet.Authentication.AuthenticationMiddleware`1.d__18.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

Microsoft.AspNet.Authentication.AuthenticationMiddleware`1.d__18.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.GetResult()

Microsoft.ApplicationInsights.AspNet.ExceptionTrackingMiddleware.d__4.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.GetResult()

Microsoft.AspNet.IISPlatformHandler.IISPlatformHandlerMiddleware.d__8.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.GetResult()

Microsoft.AspNet.Diagnostics.Entity.MigrationsEndPointMiddleware.d__5.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.GetResult()

Microsoft.AspNet.Diagnostics.Entity.DatabaseErrorPageMiddleware.d__6.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

Microsoft.AspNet.Diagnostics.Entity.DatabaseErrorPageMiddleware.d__6.MoveNext()

---从抛出异常的先前位置开始的堆栈跟踪结束---

System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(任务任务)

System.Runtime.CompilerServices.TaskAwaiter.GetResult()

Microsoft.AspNet.Diagnostics.DeveloperExceptionPageMiddleware.d__7.MoveNext()

出了什么问题？如何分析/调试跟踪？提前致谢

Column Cre_DtTm允许null.下面是表脚本:

 CREATE TABLE [dbo].[MatGrp](  [Grp_RNo] [numeric](5, 0) NOT NULL,  
 [Grp_Code] [varchar](50) NOT NULL,  [Grp_Name] [varchar](50) NOT NULL,
 [Cre_By] [numeric](3, 0) NOT NULL,  [Cre_DtTm] [datetime] NULL, 
 [Mod_By] [numeric](3, 0) NOT NULL,  [Mod_DtTm] [datetime] NULL, 
 CONSTRAINT [PK_MatGrp_Grp_RNo] PRIMARY KEY CLUSTERED  ( [Grp_RNo] ASC
 )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY =
 OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON
 [PRIMARY]
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Gan*_*esh 6

呵呵,我搞错了这个列在数据库中的表定义中允许null,但它还必须允许类中的null(？在DateTime？中允许为null)public DateTime？Cre_DtTm {get; 组; }

这解决了这个问题.

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