问候，
我在这里发布了问题（8 月 18 日的帖子是我的），但没有得到任何结果。
简而言之，使用 Telerik 的 MVC 网格进行过滤会导致 ArgumentException 出现消息“DbIsNullExpression 的参数必须引用原始类型或引用类型”。有趣的是，如果您首先 .ToList() IQueryable，则可以避免该问题（但撤回所有数据并不是一个好的解决方案）。还使用实体框架和 Ajax，不确定这是否是一个问题。这是堆栈跟踪：
System.ArgumentException was unhandled by user code
Message=The argument to DbIsNullExpression must refer to a primitive or reference type.
Source=System.Data.Entity
StackTrace:
at System.Data.Common.CommandTrees.ExpressionBuilder.Internal.ArgumentValidation.ValidateIsNull(DbExpression argument, Boolean allowRowType)
at System.Data.Objects.ELinq.ExpressionConverter.EqualsTranslator.CreateIsNullExpression(ExpressionConverter parent, Expression input)
at System.Data.Objects.ELinq.ExpressionConverter.EqualsTranslator.TypedTranslate(ExpressionConverter parent, BinaryExpression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.NotTranslator.TypedTranslate(ExpressionConverter parent, UnaryExpression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.NotEqualsTranslator.TypedTranslate(ExpressionConverter parent, BinaryExpression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.ConditionalTranslator.TypedTranslate(ExpressionConverter parent, ConditionalExpression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.BinaryTranslator.TypedTranslate(ExpressionConverter parent, BinaryExpression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TranslateIntoCanonicalFunction(String functionName, Expression Expression, Expression[] linqArguments)
at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.CanonicalFunctionDefaultTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)
at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.EqualsTranslator.TypedTranslate(ExpressionConverter parent, BinaryExpression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input)
at System.Data.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input, DbExpressionBinding& binding)
at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, DbExpression& source, DbExpressionBinding& sourceBinding, DbExpression& lambda)
at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)
at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)
at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.AggregateTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)
at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)
at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)
at System.Data.Objects.ELinq.ExpressionConverter.Convert()
at System.Data.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption)
at System.Data.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)
at System.Data.Objects.ObjectQuery`1.System.Collections.Generic.IEnumerable.GetEnumerator()
at System.Data.Objects.ObjectQuery`1.GetEnumeratorInternal()
at System.Data.Objects.ObjectQuery.System.Collections.IEnumerable.GetEnumerator()
at System.Linq.Enumerable.d__b1`1.MoveNext()
at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source)
at System.Data.Objects.ELinq.ObjectQueryProvider.b__3[TResult](IEnumerable`1 sequence)
at System.Data.Objects.ELinq.ObjectQueryProvider.ExecuteSingle[TResult](IEnumerable`1 query, Expression queryRoot)
at System.Data.Objects.ELinq.ObjectQueryProvider.System.Linq.IQueryProvider.Execute(Expression expression)
at Telerik.Web.Mvc.Extensions.QueryableExtensions.Count(IQueryable source) in C:\Projects\SoftExposure\Telerik.Web.Mvc\Extensions\QueryableExtensions.cs:line 399
at Telerik.Web.Mvc.Extensions.QueryableExtensions.ToGridModel(IQueryable queryable, Int32 page, Int32 pageSize, IList`1 sortDescriptors, IEnumerable`1 filterDescriptors, IEnumerable`1 groupDescriptors) in C:\Projects\SoftExposure\Telerik.Web.Mvc\Extensions\QueryableExtensions.cs:line 45
at Telerik.Web.Mvc.UI.GridDataProcessor.EnsureDataSourceIsProcessed() in C:\Projects\SoftExposure\Telerik.Web.Mvc\UI\Grid\GridDataProcessor.cs:line 162
at Telerik.Web.Mvc.UI.GridDataProcessor.get_ProcessedDataSource() in C:\Projects\SoftExposure\Telerik.Web.Mvc\UI\Grid\GridDataProcessor.cs:line 132
at Telerik.Web.Mvc.GridActionAttribute.OnActionExecuted(ActionExecutedContext filterContext) in C:\Projects\SoftExposure\Telerik.Web.Mvc\UI\Grid\GridActionAttribute.cs:line 104
at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)
at System.Web.Mvc.ControllerActionInvoker.c__DisplayClassd.c__DisplayClassf.b__c()
at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)
InnerException:
这是导致它的代码
// Note: We need to use a ViewModel rather than the entity directly because the entity relationships
// will cause a circular reference when used via Ajax.
// See http://www.telerik.com/help/aspnet-mvc/telerik-ui-components-grid-troubleshooting.html#ServerError
//
private IEnumerable GetCustomers()
{
var model = new NorthwindEntities().Customers
.Select(c => new CustomerModel()
{
CustomerID = c.CustomerID,
CompanyName = c.CompanyName,
ContactName = c.ContactName
}); // Call .ToList() here to avoid "The argument to DbIsNullExpression must refer to a primitive or reference type."
// when filtering.
// See http://www.telerik.com/community/forums/aspnet-mvc/grid/the-argument-to-dbisnullexpression-must-refer-to-a-primitive-or-reference-type.aspx
return model;
}
单步查看源代码，很容易看出它发生在 QueryableExtensions.Count() 方法中，但真正的原因是当一个具有 filterDescriptors 的 .Where() 方法中发生的事情。无论表达构建的东西在做什么似乎都是原因。
这是我第一次深入研究表达式树，如果有人能提出一些尝试的建议，不胜感激。
问候，迈克