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我有一个带有 odata 的 asp.net wep api 项目，但我在 odata 过滤机制方面遇到了一些问题。

当我执行该查询时

/api/values?$top=1&$filter=Comments/any(c: c/Id eq 64)

它给了我以下错误

{
"Message": "An error has occurred.",
"ExceptionMessage": "The 'ObjectContent`1' type failed to serialize the response body for content type 'application/json; charset=utf-8'.",
"ExceptionType": "System.InvalidOperationException",
"StackTrace": null,
"InnerException": {
    "Message": "An error has occurred.",
    "ExceptionMessage": "Cannot compare elements of type 'System.Linq.IQueryable`1'. Only primitive types, enumeration types and entity types are supported.",
    "ExceptionType": "System.NotSupportedException",
    "StackTrace": "   at System.Data.Objects.ELinq.ExpressionConverter.VerifyTypeSupportedForComparison(Type clrType, TypeUsage edmType, Stack`1 memberPath)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.CreateIsNullExpression(DbExpression operand, Type operandClrType)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.EqualsTranslator.CreateIsNullExpression(ExpressionConverter parent, Expression input)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.EqualsTranslator.TypedTranslate(ExpressionConverter parent, BinaryExpression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.ConditionalTranslator.TypedTranslate(ExpressionConverter parent, ConditionalExpression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.EqualsTranslator.TypedTranslate(ExpressionConverter parent, BinaryExpression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input, DbExpressionBinding& binding)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, DbExpression& source, DbExpressionBinding& sourceBinding, DbExpression& lambda)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, DbExpression& source, DbExpressionBinding& sourceBinding, DbExpression& lambda)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.UnarySequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)\r\n   at System.Data.Objects.ELinq.ExpressionConverter.Convert()\r\n   at System.Data.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption)\r\n   at System.Data.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)\r\n   at System.Data.Objects.ObjectQuery`1.System.Collections.Generic.IEnumerable<T>.GetEnumerator()\r\n   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)\r\n   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)\r\n   at Newtonsoft.Json.Serialization.JsonArrayContract.CreateWrapper(Object list)\r\n   at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)\r\n   at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value)\r\n   at Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value)\r\n   at Newtonsoft.Json.JsonSerializer.Serialize(JsonWriter jsonWriter, Object value)\r\n   at System.Net.Http.Formatting.JsonMediaTypeFormatter.<>c__DisplayClassd.<WriteToStreamAsync>b__c()\r\n   at System.Threading.Tasks.TaskHelpers.RunSynchronously(Action action, CancellationToken token)"
}

}

但是当我执行以下控制器而不是 odata 过滤器时，一切都很好，

    [Queryable]
    public IQueryable<FortuneDTO> Get()
    {
        return service.FilterBy().Where(_ => _.Comments.Any(c => c.Id == 64));
    }

我在我的项目中使用 Repository + Service 层模式，我的项目结构是这样的

api 控制器 <-> 服务 <-> 存储库 <-> EF

odata api 控制器

    [Queryable]
    public IQueryable<FortuneDTO> Get()
    {
        return service.FiterBy();
    }

服务

    public IQueryable<FortuneDTO> FiterBy()
    {
        return repository.List().Select(_ => new FortuneDTO
        {
            CreatedByFullName = _.aspnet_Users.FullName,
            Id = _.FortuneId,
            Comments = _.tblComment.Select(c => new CommentDTO
            {
                Id=c.CommentId,
                Comment = c.Comment,
                Fortuneteller = new FortunetellerDTO { 
                    FullName=c.aspnet_Users.FullName,
                    Id=c.aspnet_Users.UserId
                }
            }).AsQueryable()
        });
    }

存储库

    public virtual IQueryable<TEntity> List()
    {
        return context.CreateObjectSet<TEntity>();
    }

DTO

public class FortuneDTO
{
    public int Id { get; set; }
    public string CreatedByFullName { get; set; }
    public IQueryable<CommentDTO> Comments { get; set; }
}
public class CommentDTO
{
    public int Id { get; set; }
    public string Comment { get; set; }
    public FortunetellerDTO Fortuneteller { get; set; }
}
public class FortunetellerDTO
{
    public Guid Id { get; set; }
    public string FullName { get; set; }
}

我找不到任何方法来避免这个错误

编辑：

生成和执行的表达式是

 Convert(value(System.Data.Objects.ObjectSet`1[Axiom.Entities.tblFortune])).MergeAs(AppendOnly).Where(_ => True).Select(_ => new FortuneDTO() {CreatedByFullName = _.aspnet_Users.FullName, Id = _.FortuneId, Comments = _.tblComment.Select(c => new CommentDTO() {Id = c.CommentId, Comment = c.Comment, Fortuneteller = new FortunetellerDTO() {FullName = c.aspnet_Users.FullName, Id = c.aspnet_Users.UserId}}).AsQueryable()}).Where($it => (IIF(($it.Comments == null), null, Convert($it.Comments.Any(c => ($it.Id == value(System.Web.Http.OData.Query.Expressions.LinqParameterContainer+TypedLinqParameterContainer`1[System.Int32]).TypedProperty)))) == True))

实体框架 4 ASP.NET Web API 4.0.30506.0

4

1 回答 1

2

我认为 Web API 未能检测到您正在使用 entityframework（可能是因为您使用的是 entityframework 4.0）并且正在打开 NullPropagation。你可以通过这样做明确地关闭它，

[Queryable(HandleNullPropagation=false)]

看看它是否有效。

于 2013-09-23T17:31:12.400 回答