C# System.Reflection.TargetException。返回值为空错误

我有一个问题仍然无法解决。我有一个数据库，在保存按钮下拉列表有空的问题

这行中有空问题

var ulke = db.Ulkeler.Where(m => m.Id == model.Ulke.Id).FirstOrDefault();

你能帮我解决这个问题吗

还有数据库和下拉列表

人事学

namespace grid.Models
{
    [Table("Personeller")]
    public class Personel
    {
        [Key,DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int Id { get; set; }

    [StringLength(50),Required]
    public string Adi { get; set; }
    public string Soyadi { get; set; }
    public int Yas { get; set; }

    public Ulke Ulke { get; set; }

}
}

Ulke.cs

namespace grid.Models
{
    [Table("Ulkeler")]
    public class Ulke
    {
        [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int Id { get; set; }
        public string Ad { get; set; }

    public List<Personel> Personeller { get; set; }
}
}

问题就在这里

[TargetException: Statik olmayan metot, hedef gerektirir.]
   System.Reflection.RuntimeMethodInfo.CheckConsistency(Object target) +12788592
   System.Reflection.RuntimeMethodInfo.InvokeArgumentsCheck(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) +115
   System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) +54
   System.Reflection.RuntimePropertyInfo.GetValue(Object obj, BindingFlags invokeAttr, Binder binder, Object[] index, CultureInfo culture) +61
   System.Reflection.RuntimePropertyInfo.GetValue(Object obj, Object[] index) +21
   System.Data.Entity.Core.Objects.ELinq.QueryParameterExpression.TryGetFieldOrPropertyValue(MemberExpression me, Object instance, Object& memberValue) +195
   System.Data.Entity.Core.Objects.ELinq.QueryParameterExpression.TryEvaluatePath(Expression expression, ConstantExpression& constantExpression) +332
   System.Data.Entity.Core.Objects.ELinq.QueryParameterExpression.EvaluateParameter(Object[] arguments) +104
   System.Data.Entity.Core.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption) +1216
   System.Data.Entity.Core.Objects.<>c__DisplayClass7.<GetResults>b__6() +39
   System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction(Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess) +288
   System.Data.Entity.Core.Objects.<>c__DisplayClass7.<GetResults>b__5() +154
   System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Func`1 operation) +189
   System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption) +279
   System.Data.Entity.Core.Objects.ObjectQuery`1.<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__0() +11
   System.Data.Entity.Internal.LazyEnumerator`1.MoveNext() +45
   System.Linq.Enumerable.FirstOrDefault(IEnumerable`1 source) +121
   System.Data.Entity.Core.Objects.ELinq.ObjectQueryProvider.<GetElementFunction>b__1(IEnumerable`1 sequence) +40
   System.Data.Entity.Core.Objects.ELinq.ObjectQueryProvider.ExecuteSingle(IEnumerable`1 query, Expression queryRoot) +60
   System.Data.Entity.Core.Objects.ELinq.ObjectQueryProvider.System.Linq.IQueryProvider.Execute(Expression expression) +113
   System.Data.Entity.Internal.Linq.DbQueryProvider.Execute(Expression expression) +99
   System.Linq.Queryable.FirstOrDefault(IQueryable`1 source) +211
   grid.Controllers.GridController.Ekle(Personel model) in E:\hande\çalışma\mvc\grid-mvc-udemy\grid\grid\Controllers\GridController.cs:46
   lambda_method(Closure , ControllerBase , Object[] ) +103
   System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +14
   System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +157
   System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +27
   System.Web.Mvc.Async.<>c.<BeginInvokeSynchronousActionMethod>b__9_0(IAsyncResult asyncResult, ActionInvocation innerInvokeState) +22
   System.Web.Mvc.Async.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult) +29
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) +32
   System.Web.Mvc.Async.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__11_0() +50
   System.Web.Mvc.Async.<>c__DisplayClass11_1.<InvokeActionMethodFilterAsynchronouslyRecursive>b__2() +228
   System.Web.Mvc.Async.<>c__DisplayClass7_0.<BeginInvokeActionMethodWithFilters>b__1(IAsyncResult asyncResult) +10
   System.Web.Mvc.Async.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult) +10
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) +34
   System.Web.Mvc.Async.<>c__DisplayClass3_6.<BeginInvokeAction>b__3() +35
   System.Web.Mvc.Async.<>c__DisplayClass3_1.<BeginInvokeAction>b__5(IAsyncResult asyncResult) +100
   System.Web.Mvc.Async.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult) +10
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +27
   System.Web.Mvc.<>c.<BeginExecuteCore>b__152_1(IAsyncResult asyncResult, ExecuteCoreState innerState) +11
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +29
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +45
   System.Web.Mvc.<>c.<BeginExecute>b__151_2(IAsyncResult asyncResult, Controller controller) +13
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +22
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +26
   System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +10
   System.Web.Mvc.<>c.<BeginProcessRequest>b__20_1(IAsyncResult asyncResult, ProcessRequestState innerState) +28
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +29
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +28
   System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +576
   System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step) +132
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +163

[目标例外：Statik olmayan metot，hedef gerektirir.]
System.Reflection.RuntimeMethodInfo.CheckConsistency（对象目标）+12788592
System.Reflection.RuntimeMethodInfo.InvokeArgumentsCheck（对象对象obj、BindingFlags invokeAttr、绑定器Binder、对象[]参数、CultureInfo区域性）+115
System.Reflection.RuntimeMethodInfo.Invoke（对象obj、BindingFlags invokeAttr、Binder Binder、对象[]参数、CultureInfo区域性）+54
System.Reflection.RuntimePropertyInfo.GetValue（对象obj、BindingFlags invokeAttr、绑定器Binder、对象[]索引、CultureInfo区域性）+61
System.Reflection.RuntimePropertyInfo.GetValue（对象obj，对象[]索引）+21
System.Data.Entity.Core.Objects.Elink.QueryParameterExpression.TryGetFieldOrPropertyValue（MemberExpression me、对象实例、对象和成员值）+195
System.Data.Entity.Core.Objects.Elink.QueryParameterExpression.TryEvaluatePath（表达式表达式、常量表达式和常量表达式）+332
System.Data.Entity.Core.Objects.Elink.QueryParameterExpression.EvaluateParameter（对象[]参数）+104
System.Data.Entity.Core.Objects.elink.elinkQueryState.GetExecutionPlan（可空`1 forMergeOption）+1216
System.Data.Entity.Core.Objects.c__DisplayClass7.b__6（）+39
System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction（Func`1 Func，IDBecutionStrategy executionStrategy，Boolean startLocalTransaction，Boolean releaseConnectionOnSuccess）+288
System.Data.Entity.Core.Objects.c__DisplayClass7.b__5（）+154
System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute（Func`1操作）+189
System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults（可为null`1 forMergeOption）+279
System.Data.Entity.Core.Objects.ObjectQuery`1.b__0（）+11
System.Data.Entity.Internal.LazyEnumerator`1.MoveNext（）+45
System.Linq.Enumerable.FirstOrDefault（IEnumerable`1源）+121
System.Data.Entity.Core.Objects.Elink.ObjectQueryProvider.b__1（IEnumerable`1序列）+40
System.Data.Entity.Core.Objects.elink.ObjectQueryProvider.ExecuteSingle（IEnumerable`1查询，表达式queryRoot）+60
System.Data.Entity.Core.Objects.elink.ObjectQueryProvider.System.Linq.IQueryProvider.Execute（表达式）+113
System.Data.Entity.Internal.Linq.DbQueryProvider.Execute（表达式）+99
System.Linq.Queryable.FirstOrDefault（IQueryable`1源）+211
E:\hande\çalışma\mvc\grid mvc udemy\grid\grid\Controllers\gridcontrollers\GridController.Ekle（个人模型）中的grid.Controllers.Ekle
lambda_方法（闭包、控制器库、对象[]）+103
System.Web.Mvc.ActionMethodDispatcher.Execute（ControllerBase控制器，对象[]参数）+14
System.Web.Mvc.ReflectedActionDescriptor.Execute（ControllerContext ControllerContext，IDictionary`2参数）+157
System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod（ControllerContext ControllerContext，ActionDescriptor ActionDescriptor，IDictionary`2参数）+27
System.Web.Mvc.Async.c.b_9_0（IAsyncResult asyncResult，ActionInvocation innerInvokeState）+22
System.Web.Mvc.Async.WrappedAsyncResult`2.CallEndDelegate（IAsyncResult asyncResult）+29
System.Web.Mvc.Async.WrappedAsyncResultBase`1.End（）+49
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod（IAsyncResult asyncResult）+32
System.Web.Mvc.Async.AsyncInvocationWithFilters.b_u11_0（）+50
System.Web.Mvc.Async.c_uuuudisplayClass11_1.b_uuu2（）+228
System.Web.Mvc.Async.c__显示类7_0.b__1（IAsyncResult asyncResult）+10
System.Web.Mvc.Async.WrappedAsyncResult`1.CallEndDelegate（IAsyncResult asyncResult）+10
System.Web.Mvc.Async.WrappedAsyncResultBase`1.End（）+49
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters（IAsyncResult asyncResult）+34
System.Web.Mvc.Async.c__显示类3_6.b__3（）+35
System.Web.Mvc.Async.c__显示类3_1.b_5（IAsyncResult asyncResult）+100
System.Web.Mvc.Async.WrappedAsyncResult`1.CallEndDelegate（IAsyncResult asyncResult）+10
System.Web.Mvc.Async.WrappedAsyncResultBase`1.End（）+49
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction（IAsyncResult asyncResult）+27
System.Web.Mvc.c.b__152_1（IAsyncResult asyncResult，ExecuteCorerate innerState）+11
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate（IAsyncResult asyncResult）+29
System.Web.Mvc.Async.WrappedAsyncResultBase`1.End（）+49
System.Web.Mvc.Controller.EndExecuteCore（IAsyncResult asyncResult）+45
System.Web.Mvc.c.b__151_2（IAsyncResult asyncResult，Controller）+13
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate（IAsyncResult asyncResult）+22
System.Web.Mvc.Async.WrappedAsyncResultBase`1.End（）+49
System.Web.Mvc.Controller.EndExecute（IAsyncResult asyncResult）+26
System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute（IAsyncResult asyncResult）+10
System.Web.Mvc.c.b_20_1（IAsyncResult asyncResult，ProcessRequestState innerState）+28
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate（IAsyncResult asyncResult）+29
System.Web.Mvc.Async.WrappedAsyncResultBase`1.End（）+49
System.Web.Mvc.MvcHandler.EndProcessRequest（IAsyncResult asyncResult）+28
System.Web.Mvc.MvcHandler.System.Web.IHTTPassynchandler.EndProcessRequest（IAsyncResult结果）+9
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute（）+576
System.Web.HttpApplication.ExecuteStepImpl（IExecutionStep步骤）+132
System.Web.HttpApplication.ExecuteStep（IExecutionStep步骤，布尔值&同步完成）+163

您能否更清楚地描述问题（在问题中，

[HttpPost]
    public ActionResult Ekle(Personel model)
    {
        var ulke = db.Ulkeler.Where(m => m.Id == model.Ulke.Id).FirstOrDefault();
        model.Ulke = ulke;

        db.Personeller.Add(model);
        db.SaveChanges();

        return RedirectToAction("Listele");
    }

[TargetException: Statik olmayan metot, hedef gerektirir.]
   System.Reflection.RuntimeMethodInfo.CheckConsistency(Object target) +12788592
   System.Reflection.RuntimeMethodInfo.InvokeArgumentsCheck(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) +115
   System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) +54
   System.Reflection.RuntimePropertyInfo.GetValue(Object obj, BindingFlags invokeAttr, Binder binder, Object[] index, CultureInfo culture) +61
   System.Reflection.RuntimePropertyInfo.GetValue(Object obj, Object[] index) +21
   System.Data.Entity.Core.Objects.ELinq.QueryParameterExpression.TryGetFieldOrPropertyValue(MemberExpression me, Object instance, Object& memberValue) +195
   System.Data.Entity.Core.Objects.ELinq.QueryParameterExpression.TryEvaluatePath(Expression expression, ConstantExpression& constantExpression) +332
   System.Data.Entity.Core.Objects.ELinq.QueryParameterExpression.EvaluateParameter(Object[] arguments) +104
   System.Data.Entity.Core.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption) +1216
   System.Data.Entity.Core.Objects.<>c__DisplayClass7.<GetResults>b__6() +39
   System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction(Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess) +288
   System.Data.Entity.Core.Objects.<>c__DisplayClass7.<GetResults>b__5() +154
   System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Func`1 operation) +189
   System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption) +279
   System.Data.Entity.Core.Objects.ObjectQuery`1.<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__0() +11
   System.Data.Entity.Internal.LazyEnumerator`1.MoveNext() +45
   System.Linq.Enumerable.FirstOrDefault(IEnumerable`1 source) +121
   System.Data.Entity.Core.Objects.ELinq.ObjectQueryProvider.<GetElementFunction>b__1(IEnumerable`1 sequence) +40
   System.Data.Entity.Core.Objects.ELinq.ObjectQueryProvider.ExecuteSingle(IEnumerable`1 query, Expression queryRoot) +60
   System.Data.Entity.Core.Objects.ELinq.ObjectQueryProvider.System.Linq.IQueryProvider.Execute(Expression expression) +113
   System.Data.Entity.Internal.Linq.DbQueryProvider.Execute(Expression expression) +99
   System.Linq.Queryable.FirstOrDefault(IQueryable`1 source) +211
   grid.Controllers.GridController.Ekle(Personel model) in E:\hande\çalışma\mvc\grid-mvc-udemy\grid\grid\Controllers\GridController.cs:46
   lambda_method(Closure , ControllerBase , Object[] ) +103
   System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +14
   System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +157
   System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +27
   System.Web.Mvc.Async.<>c.<BeginInvokeSynchronousActionMethod>b__9_0(IAsyncResult asyncResult, ActionInvocation innerInvokeState) +22
   System.Web.Mvc.Async.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult) +29
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) +32
   System.Web.Mvc.Async.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__11_0() +50
   System.Web.Mvc.Async.<>c__DisplayClass11_1.<InvokeActionMethodFilterAsynchronouslyRecursive>b__2() +228
   System.Web.Mvc.Async.<>c__DisplayClass7_0.<BeginInvokeActionMethodWithFilters>b__1(IAsyncResult asyncResult) +10
   System.Web.Mvc.Async.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult) +10
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) +34
   System.Web.Mvc.Async.<>c__DisplayClass3_6.<BeginInvokeAction>b__3() +35
   System.Web.Mvc.Async.<>c__DisplayClass3_1.<BeginInvokeAction>b__5(IAsyncResult asyncResult) +100
   System.Web.Mvc.Async.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult) +10
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +27
   System.Web.Mvc.<>c.<BeginExecuteCore>b__152_1(IAsyncResult asyncResult, ExecuteCoreState innerState) +11
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +29
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +45
   System.Web.Mvc.<>c.<BeginExecute>b__151_2(IAsyncResult asyncResult, Controller controller) +13
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +22
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +26
   System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +10
   System.Web.Mvc.<>c.<BeginProcessRequest>b__20_1(IAsyncResult asyncResult, ProcessRequestState innerState) +28
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +29
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +28
   System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +576
   System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step) +132
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +163