无法将类型'System.Nullable`1 [[System.Int32，...]]'强制转换为类型'System.Object'

时间：2019-08-07 18:41:38

标签： c# entity-framework odata wcf-data-services

我当前正在尝试通过WCF服务使用OData和Entity Framework返回dbset。我可以在数据上下文中点击dbset属性上的getter，但是当它返回时会出现错误：

  

LINQ to Entities仅支持强制转换EDM基本类型或枚举类型

最初，我认为这是由于我在实体模型中具有可为空的外键，但是在删除所有可为null的int类型之后，我仍然会收到错误消息。

MyDataContext.cs 

  public class MyDataContext : DbContext, IMyDataContext, IMyDbContextFactory
    {
        /// <summary>
        /// Default Constructor
        /// </summary>
        public MyDataContext()
        {

        }

        /// <summary>
        /// ConnectionString Constructor
        /// </summary>
        /// <param name="connectionString">Sets the initial connection string</param>
        public MyDataContext(string connectionString) : base(connectionString)
        {
            this.ConnectionString = connectionString;
        }

        public string ConnectionString { get; set; }

        #region Global Resources
        public DbSet<MyResource> MyResource{ get; set; }

        #region Ranges
        public DbSet<TheRanges> TheRanges { get; set; }

        public DbSet<TheRangesSub> TheRangesSub { get; set; }

        #region EF Model Configuration

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.RegisterEntityType(typeof(MyResource));
            modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
            base.OnModelCreating(modelBuilder);
        }
}

MyResource.cs 

    [Table("MyResource")]
    [DataServiceKey("Id")]
    public class MyResource
    {
        [Key]
        public int Id { get; set; }

        [MaxLength(255)]
        [Required(AllowEmptyStrings = true)]
        public string Title { get; set; }

        [MaxLength(255)]
        [Required(AllowEmptyStrings = true)]
        public string MyResource { get; set; }

        public string Description { get; set; }

        [Required]
        public bool SomeStandard { get; set; }

        [MaxLength(255)]
        [Required(AllowEmptyStrings = true)]
        public string CreatedDateTime { get; set; }

        [MaxLength(255)]
        [Required(AllowEmptyStrings = true)]
        public string ModifiedDateTime { get; set; }

        public DateTime Modified { get; set; }

        public DateTime Created { get; set; }

    }

TheRanges.cs 

    [Table("TheRanges")]
    [DataServiceKey("Id")]
    [EnableQuery]
    public class TheRanges
    {
        [Key]
        public int Id { get; set; }

        public string Title { get; set; }

        [Required]
        public int MyResourceId { get; set; }

        [ForeignKey(nameof(MyResourceId))]
        public MyResource MyResource { get; set; }

        [Required]
        public int someIntField { get; set; }

        public string LinkId { get; set; }

        [MaxLength(255)]
        [Required(AllowEmptyStrings = true)]
        public string CreatedDateTime { get; set; }

        [MaxLength(255)]
        [Required(AllowEmptyStrings = true)]
        public string ModifiedDateTime { get; set; }

        public DateTime Modified { get; set; }

        public DateTime Created { get; set; }
    }

TheRangesSub.cs 

  [Table("TheRangesSub")]
    [DataServiceKey("Id")]
    public class TheRangesSub
    {
        [Key]
        public int Id { get; set; }

        public string Title { get; set; }

        [Required] 
        public int TheRangesId { get; set; }

        [ForeignKey(nameof(TheRangesId))]
        public TheRanges TheRanges { get; set; }

        public string FacilityNum { get; set; }

        [Required]
        public int SomeOtherInt { get; set; }

        public string LinkId { get; set; } 

        [MaxLength(255)]
        [Required(AllowEmptyStrings = true)]
        public string RangeName { get; set; }

        [MaxLength(255)]
        [Required(AllowEmptyStrings = true)]
        public string CreatedDateTime { get; set; }

        [MaxLength(255)]
        [Required(AllowEmptyStrings = true)]
        public string ModifiedDateTime { get; set; }

        public DateTime Modified { get; set; }

        public DateTime Created { get; set; }
    }

MyService.cs 

    [BasicHttpBindingServiceMetadataExchangeEndpoint]
    [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Required)]
    [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall, IncludeExceptionDetailInFaults = true)]
    public class MyService : DataService<MyDataContext>
    {
        private SPWeb _web;
        private string connectionString;

        #region Constructor
        /// <summary>
        /// Default constructor
        /// </summary>
        public MyService() : base()
        {

        }

        #endregion
        #region Methods

        protected override MyDataContext CreateDataSource()
        {
            return new MyDataContext("MyConnectionString");
        }


        public static void InitializeService(DataServiceConfiguration config)
        {
            config.SetEntitySetAccessRule("TheRanges", EntitySetRights.AllRead);
            config.SetEntitySetAccessRule("TheRangesSub", EntitySetRights.AllRead);
            config.SetEntitySetAccessRule("MyResource", EntitySetRights.AllRead);
            config.DataServiceBehavior.MaxProtocolVersion = System.Data.Services.Common.DataServiceProtocolVersion.V2;
            config.UseVerboseErrors = true;
        }
        #endregion

让我知道我更改名字时是否发生命名不一致

我的MyResource数据库中有1个项目，因此我希望将其退回。 我正在执行的OData查询是： http://myurl/MyData.svc/MyResource？$ select = Id

运行调试器时，代码中最后被击中的地方是“ get”：

DbSet<MyResource> MyResource {get; set;}

但是，这是我当前遇到的错误：

This XML file does not appear to have any style information associated with it. The document tree is shown below.
<error xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata">
<code/>
<message xml:lang="en-US">An error occurred while processing this request.</message>
<innererror>
<message>
Unable to cast the type 'System.Nullable`1[[System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]' to type 'System.Object'. LINQ to Entities only supports casting EDM primitive or enumeration types.
</message>
<type>System.NotSupportedException</type>
<stacktrace>
at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.ValidateAndAdjustCastTypes(TypeUsage toType, TypeUsage fromType, Type toClrType, Type fromClrType)
 at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.GetCastTargetType(TypeUsage fromType, Type toClrType, Type fromClrType, Boolean preserveCastForDateTime)
 at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.CreateCastExpression(DbExpression source, Type toClrType, Type fromClrType)
 at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.ConvertTranslator.TranslateUnary(ExpressionConverter parent, UnaryExpression unary, DbExpression operand)
 at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)
 at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MemberInitTranslator.TypedTranslate(ExpressionConverter parent, MemberInitExpression linq)
 at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)
 at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.ConditionalTranslator.TypedTranslate(ExpressionConverter parent, ConditionalExpression linq)
 at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)
 at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input)
 at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, DbExpression& source, DbExpressionBinding& sourceBinding, DbExpression& lambda)
 at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SelectTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)
 at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)
 at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)
 at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.Convert()
 at System.Data.Entity.Core.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption)
 at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClass7.<GetResults>b__6()
 at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)
 at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClass7.<GetResults>b__5()
 at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func`1 operation)
 at System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)
 at System.Data.Entity.Core.Objects.ObjectQuery`1.<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__0()
 at System.Data.Entity.Internal.LazyEnumerator`1.MoveNext()
 at System.Data.Services.DataService`1.SerializeResponseBody(RequestDescription description, IDataService dataService)
 at System.Data.Services.DataService`1.HandleRequest()
</stacktrace>
</innererror>
</error>

编辑：因此，仅使用查询字符串“ http://myurl/MyData.svc/MyResource”就可以从数据库中检索我的商品，但是由于以下原因，我无法使用$ select和一些属性来获取商品：无法转换类型错误。我也可以在实体上运行$ filter和$ count。看来这只是一个$ select问题。

0 个答案:

没有答案
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