我在 ASP.NET Core 应用程序和 Controller 操作中使用 Entity Framework Core，我没有对工作代码和数据库进行任何更改，但我无法判断查询性能如何......

我在 ASP.NET Core 应用程序和 Controller 操作中使用 Entity Framework Core，我没有对工作代码和数据库进行任何更改，但我无法分辨 Entity Framework Core 执行的查询是什么。

控制器动作：

[HttpGet]
// GET: Administration/Companies
public async Task<ActionResult> Index()
{
    var users = await UserManager.Users.ToListAsync();

    var companyEditVMs = await DB.Companies
    .OrderBy(company => company.CompanyId == 1 
        ? "_" + company.CompanyName 
        : company.CompanyName
    )
    Select(a => new CompanyEditVM(HttpContext, a, users.Where(b => b.CompanyId == a.CompanyId)))
    .ToListAsync();

    return View(companyEditVMs);
}

踪迹

SqlNullValueException: Data is Null. This method or property cannot be called on Null values.
System.Data.SqlClient.SqlBuffer.get_String()
System.Data.SqlClient.SqlDataReader.GetString(int i)
lambda_method(Closure , DbDataReader )
Microsoft.EntityFrameworkCore.Storage.Internal.TypedRelationalValueBufferFactory.Create(DbDataReader dataReader)
Microsoft.EntityFrameworkCore.Query.Internal.AsyncQueryingEnumerable<T>+AsyncEnumerator.BufferlessMoveNext(DbContext _, bool buffer, CancellationToken cancellationToken)
Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerExecutionStrategy.ExecuteAsync<TState, TResult>(TState state, Func<DbContext, TState, CancellationToken, Task<TResult>> operation, Func<DbContext, TState, CancellationToken, Task<ExecutionResult<TResult>>> verifySucceeded, CancellationToken cancellationToken)
Microsoft.EntityFrameworkCore.Query.Internal.AsyncQueryingEnumerable<T>+AsyncEnumerator.MoveNext(CancellationToken cancellationToken)
Microsoft.EntityFrameworkCore.Query.Internal.AsyncLinqOperatorProvider+ExceptionInterceptor<T>+EnumeratorExceptionInterceptor.MoveNext(CancellationToken cancellationToken)
System.Linq.AsyncEnumerable.Aggregate_<TSource, TAccumulate, TResult>(IAsyncEnumerable<TSource> source, TAccumulate seed, Func<TAccumulate, TSource, TAccumulate> accumulator, Func<TAccumulate, TResult> resultSelector, CancellationToken cancellationToken) in Aggregate.cs
KYC.Core.Areas.Commercial.Controllers.CompaniesController.Index() in CompaniesController.cs
-
        [HttpGet]
        // GET: Administration/Companies
        public async Task<ActionResult> Index()
        {
            var users = await UserManager.Users.ToListAsync();

            var companyEditVMs = await DB.Companies
                .OrderBy(company => company.CompanyId == 1 
                    ? "_" + company.CompanyName 
                    : company.CompanyName
                )
                .Select(a => new CompanyEditVM(HttpContext, a, users.Where(b => b.CompanyId == a.CompanyId)))
                .ToListAsync();
lambda_method(Closure , object )
Microsoft.Extensions.Internal.ObjectMethodExecutorAwaitable+Awaiter.GetResult()
Microsoft.AspNetCore.Mvc.Internal.ActionMethodExecutor+TaskOfActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, object controller, object[] arguments)
System.Threading.Tasks.ValueTask<TResult>.get_Result()

我甚至尝试这样做 var companies = await DB.Companies.ToListAsync() 。但我遇到了完全相同的异常。

也许我希望能够获取 EF Core 执行的查询并手动执行此操作，以便我可以尝试找出查询的问题所在。

我想知道可能发生了什么。尤其是因为其他实体（如用户或国家）仍然可以从数据库中获取。

我知道如何解决实际的根本问题吗？

[编辑]

在“代码”中唯一真正改变的是 nuget 引用，我基本上升级了几乎所有内容，虽然它没有破坏代码中的引用，但它似乎改变了 EF Core 以某种方式（猜测）解释数据库的方式。

我确实将我的 git 存储库重置到了 nuget 包更新发生之前的时间点，一切正常。，。然后我决定将 EntityFrameworkCore 从 2.0.2 更新到 2.2.4（也尝试了 2.2.0，结果相同），问题再次发生......不确定 2.0.2 和 2.2.0 之间发生了什么变化导致此异常（但模型是相同的，只是 EF Core 版本发生了变化）...

这是实体定义，它似乎是使用数据库表/模式中的工具自动生成的：

    [Table("T_Companies")]
    public partial class Company : INotifyPropertyChanging, INotifyPropertyChanged
    {
        public override string ToString()
        {
            return CompanyId + " " + CompanyName;
        }

        private static PropertyChangingEventArgs emptyChangingEventArgs = new PropertyChangingEventArgs(string.Empty);

        private int _CompanyId;

        private string _CompanyName;

        private int _CompanyTypeId;

        private int _CountryId;

        private string _CompanyVatNumber;

        private string _CompanyStreetAddress;

        private string _CompanyZipCode;

        private string _CompanyCity;

        private string _ContactLastName;

        private string _ContactFirstName;

        private bool? _Active;

        private int? _AccountId;

        private string _CallbackSalt;

        private int? _UserSpaceId;

        private string _Login;

        private string _Pwd;

        private bool _IsTechnicalAccount;

        private DateTime? _StatusDate;

        private int _BankStatusCode;

        private string _PivotalAccount;

        private CompanyType _CompanyType;

        private Country _Country;

        private bool _IsKycIdSent;

        #region Extensibility Method Definitions
        partial void OnLoaded();
        partial void OnCreated();
        partial void OnCompanyIdChanging(int value);
        partial void OnCompanyIdChanged();
        partial void OnCompanyNameChanging(string value);
        partial void OnCompanyNameChanged();

        partial void OnCompanyCityChanging(string value);
        partial void OnCompanyCityChanged();
        partial void OnCompanyZipCodeChanging(string value);
        partial void OnCompanyZipCodeChanged();
        partial void OnContactLastNameChanging(string value);
        partial void OnContactLastNameChanged();
        partial void OnActiveChanging(bool? value);
        partial void OnActiveChanged();
        partial void OnCompanyTypeIdChanging(int value);
        partial void OnCompanyTypeIdChanged();
        partial void OnCountryIdChanging(int value);
        partial void OnCountryIdChanged();
        partial void OnContactFirstNameChanging(string value);
        partial void OnContactFirstNameChanged();
        partial void OnCompanyVatNumberChanging(string value);
        partial void OnCompanyVatNumberChanged();
        partial void OnCompanyStreetAddressChanged();
        partial void OnCompanyStreetAddressChanging(string value);
        partial void OnAccountIdChanging(int? value);
        partial void OnAccountIdChanged();
        partial void OnCallbackSaltChanging(string value);
        partial void OnCallbackSaltChanged();
        partial void OnUserSpaceIdChanging(int? value);
        partial void OnUserSpaceIdChanged();
        partial void OnLoginChanging(string value);
        partial void OnLoginChanged();
        partial void OnPwdChanging(string value);
        partial void OnPwdChanged();
        partial void OnIsTechnicalAccountChanging(bool value);
        partial void OnIsTechnicalAccountChanged();
        partial void OnStatusDateChanging(DateTime? value);
        partial void OnStatusDateChanged();
        partial void OnBankStatusCodeChanging(int value);
        partial void OnBankStatusCodeChanged();
        partial void OnPivotalAccountChanging(string value);
        partial void OnPivotalAccountChanged();
        partial void OnIsKycIdSentChanging(bool value);
        partial void OnIsKycIdSentChanged();

        #endregion

        public Company()
        {
            OnCreated();
        }

        [Key, Column("CompanyId"), DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int CompanyId
        {
            get => _CompanyId;
            set
            {
                if (_CompanyId != value)
                {
                    OnCompanyIdChanging(value);
                    SendPropertyChanging();
                    _CompanyId = value;
                    SendPropertyChanged("CompanyId");
                    OnCompanyIdChanged();
                }
            }
        }

        [DataType(DataType.Text), StringLength(1024), Column("CompanyName"), Required]
        public string CompanyName
        {
            get => _CompanyName;
            set
            {
                if (_CompanyName != value)
                {
                    OnCompanyNameChanging(value);
                    SendPropertyChanging();
                    _CompanyName = value;
                    SendPropertyChanged("CompanyName");
                    OnCompanyNameChanged();
                }
            }
        }

        [Column("CompanyTypeId"), Required]
        public int CompanyTypeId
        {
            get => _CompanyTypeId;
            set
            {
                if (_CompanyTypeId != value)
                {
                    OnCompanyTypeIdChanging(value);
                    SendPropertyChanging();
                    _CompanyTypeId = value;
                    SendPropertyChanged("CompanyTypeId");
                    OnCompanyTypeIdChanged();
                }
            }
        }


        [Column("CountryId"), Required]
        public int CountryId
        {
            get => _CountryId;
            set
            {
                if (CountryId != value)
                {
                    OnCountryIdChanging(value);
                    SendPropertyChanging();
                    _CountryId = value;
                    SendPropertyChanged("CountryId");
                    OnCountryIdChanged();
                }
            }
        }


        [DataType(DataType.Text), StringLength(100), Column("CompanyCity"), Required]
        public string CompanyCity
        {
            get => _CompanyCity;
            set
            {
                if (_CompanyCity != value)
                {
                    OnCompanyCityChanging(value);
                    SendPropertyChanging();
                    _CompanyCity = value;
                    SendPropertyChanged("CompanyCity");
                    OnCompanyCityChanged();
                }
            }
        }

        [DataType(DataType.Text), StringLength(100), Column("CompanyStreetAddress"), Required]
        public string CompanyStreetAddress
        {
            get => _CompanyStreetAddress;
            set
            {
                if (_CompanyStreetAddress != value)
                {
                    OnCompanyStreetAddressChanging(value);
                    SendPropertyChanging();
                    _CompanyStreetAddress = value;
                    SendPropertyChanged("CompanyStreetAddress");
                    OnCompanyStreetAddressChanged();
                }
            }
        }

        [DataType(DataType.Text), StringLength(30), Column("CompanyVatNumber"), Required]
        public string CompanyVatNumber
        {
            get => _CompanyVatNumber;
            set
            {
                if (_CompanyVatNumber != value)
                {
                    OnCompanyVatNumberChanging(value);
                    SendPropertyChanging();
                    _CompanyVatNumber = value;
                    SendPropertyChanged("CompanyVatNumber");
                    OnCompanyVatNumberChanged();
                }
            }
        }


        [DataType(DataType.Text), StringLength(10), Column("CompanyZipCode"), Required]
        public string CompanyZipCode
        {
            get => _CompanyZipCode;
            set
            {
                if (_CompanyZipCode != value)
                {
                    OnCompanyZipCodeChanging(value);
                    SendPropertyChanging();
                    _CompanyZipCode = value;
                    SendPropertyChanged("CompanyZipCode");
                    OnCompanyZipCodeChanged();
                }
            }
        }


        [DataType(DataType.Text), StringLength(1024), Column("ContactLastName"), Required]
        public string ContactLastName
        {
            get => _ContactLastName;
            set
            {
                if (_ContactLastName != value)
                {
                    OnContactLastNameChanging(value);
                    SendPropertyChanging();
                    _ContactLastName = value;
                    SendPropertyChanged("ContactLastName");
                    OnContactLastNameChanged();
                }
            }
        }

        [DataType(DataType.Text), StringLength(1024), Column("ContactFirstName"), Required]
        public string ContactFirstName
        {
            get => _ContactFirstName;
            set
            {
                if (_ContactFirstName != value)
                {
                    OnContactFirstNameChanging(value);
                    SendPropertyChanging();
                    _ContactFirstName = value;
                    SendPropertyChanged("ContactFirstName");
                    OnContactFirstNameChanged();
                }
            }
        }

        [Column("Active"), Required]
        public bool? Active
        {
            get => _Active;
            set
            {
                if (_Active != value)
                {
                    OnActiveChanging(value);
                    SendPropertyChanging();
                    _Active = value;
                    SendPropertyChanged("Active");
                    OnActiveChanged();
                }
            }
        }

        [Column("AccountId")]
        public int? AccountId
        {
            get => _AccountId;
            set
            {
                if (_AccountId != value)
                {
                    OnAccountIdChanging(value);
                    SendPropertyChanging();
                    _AccountId = value;
                    SendPropertyChanged("AccountId");
                    OnAccountIdChanged();
                }
            }
        }

        [DataType(DataType.Text), StringLength(1024), Column("CallbackSalt")]
        public string CallbackSalt
        {
            get => _CallbackSalt;
            set
            {
                if (_CallbackSalt != value)
                {
                    OnCallbackSaltChanging(value);
                    SendPropertyChanging();
                    _CallbackSalt = value;
                    SendPropertyChanged("CallbackSalt");
                    OnCallbackSaltChanged();
                }
            }
        }

        [Column("UserSpaceId")]
        public int? UserSpaceId
        {
            get => _UserSpaceId;
            set
            {
                if (_UserSpaceId != value)
                {
                    OnUserSpaceIdChanging(value);
                    SendPropertyChanging();
                    _UserSpaceId = value;
                    SendPropertyChanged("UserSpaceId");
                    OnUserSpaceIdChanged();
                }
            }
        }

        [DataType(DataType.Text), StringLength(1024), Column("Login")]
        public string Login
        {
            get => _Login;
            set
            {
                if (_Login != value)
                {
                    OnLoginChanging(value);
                    SendPropertyChanging();
                    _Login = value;
                    SendPropertyChanged("Login");
                    OnLoginChanged();
                }
            }
        }

        [DataType(DataType.Text), StringLength(1024), Column("Pwd")]
        public string Pwd
        {
            get => _Pwd;
            set
            {
                if (_Pwd != value)
                {
                    OnPwdChanging(value);
                    SendPropertyChanging();
                    _Pwd = value;
                    SendPropertyChanged("Pwd");
                    OnPwdChanged();
                }
            }
        }

        [Column("IsTechnicalAccount"), Required]
        public bool IsTechnicalAccount
        {
            get => _IsTechnicalAccount;
            set
            {
                if (_IsTechnicalAccount != value)
                {
                    OnIsTechnicalAccountChanging(value);
                    SendPropertyChanging();
                    _IsTechnicalAccount = value;
                    SendPropertyChanged("IsTechnicalAccount");
                    OnIsTechnicalAccountChanged();
                }
            }
        }

        [DataType(DataType.DateTime), Column("StatusDate")]
        public DateTime? StatusDate
        {
            get => _StatusDate;
            set
            {
                if (_StatusDate != value)
                {
                    OnStatusDateChanging(value);
                    SendPropertyChanging();
                    _StatusDate = value;
                    SendPropertyChanged("StatusDate");
                    OnStatusDateChanged();
                }
            }
        }

        [Column("BankStatusCode")]
        public int BankStatusCode
        {
            get => _BankStatusCode;
            set
            {
                if (_BankStatusCode != value)
                {
                    OnBankStatusCodeChanging(value);
                    SendPropertyChanging();
                    _BankStatusCode = value;
                    SendPropertyChanged("BankStatusCode");
                    OnBankStatusCodeChanged();
                }
            }
        }

        [DataType(DataType.Text), StringLength(255), Column("PivotalAccount")]
        public string PivotalAccount
        {
            get => _PivotalAccount;
            set
            {
                if (_PivotalAccount != value)
                {
                    OnPivotalAccountChanging(value);
                    SendPropertyChanging();
                    _PivotalAccount = value;
                    SendPropertyChanged("PivotalAccount");
                    OnPivotalAccountChanged();
                }
            }
        }

        public List<Resultat> Resultats { get; set; }

        public CompanyType CompanyType
        {
            get => _CompanyType;
            set
            {
                var previousValue = _CompanyType;
                if (previousValue != value)
                {
                    SendPropertyChanging();
                    _CompanyType = value;
                    if (value != null)
                    {
                        CompanyTypeId = value.CompanyTypeId;
                    }
                    else
                    {
                        _CompanyTypeId = default;
                    }
                    SendPropertyChanged("CompanyType");
                }
            }
        }

        public Country Country
        {
            get => _Country;
            set
            {
                var previousValue = _Country;
                if (previousValue != value)
                {
                    SendPropertyChanging();
                    _Country = value;
                    _CountryId = value?.CountryId ?? default;
                    SendPropertyChanged("Country");
                }
            }
        }

        [Column("IsKycIdSent"), Required]
        public bool IsKycIdSent
        {
            get => _IsKycIdSent;
            set
            {
                if (_IsKycIdSent != value)
                {
                    OnIsKycIdSentChanging(value);
                    SendPropertyChanging();
                    _IsKycIdSent = value;
                    SendPropertyChanged("IsKycIdSent");
                    OnIsKycIdSentChanged();
                }
            }
        }

        public event PropertyChangingEventHandler PropertyChanging;

        public event PropertyChangedEventHandler PropertyChanged;

        protected virtual void SendPropertyChanging()
        {
            PropertyChanging?.Invoke(this, emptyChangingEventArgs);
        }

        protected virtual void SendPropertyChanged(string propertyName)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }

        private void Attach_Resultats(Resultat entity)
        {
            SendPropertyChanging();
            entity.Company = this;
        }

        private void Detach_Resultats(Resultat entity)
        {
            SendPropertyChanging();
            entity.Company = null;
        }
    }

以及相关的表创建脚本：

create table T_Companies
(
    CompanyId            int identity (10) identity
        primary key nonclustered,
    CompanyName          varchar(1024) not null,
    CompanyTypeId        int           not null
        constraint FK_Company_CompanyType
            references T_CompanyTypes,
    CountryId            int           not null
        constraint FK_Company_Country
            references T_Countries,
    Active               bit           not null,
    AccountId            int,
    CallbackSalt         varchar(1024),
    UserSpaceId          int,
    Login                varchar(1024),
    Pwd                  varchar(1024),
    StatusDate           datetime(23, 3),
    BankStatusCode       int           not null,
    PivotalAccount       varchar(255),
    IsTechnicalAccount   bit           not null,
    CompanyStreetAddress varchar(256),
    CompanyCity          varchar(256),
    CompanyZipCode       varchar(10),
    CompanyVatNumber     varchar(30),
    ContactFirstName     varchar(20),
    ContactLastName      varchar(20),
    IsKycIdSent          bit           not null
)
go

[编辑2]

对于完全相同的模型，这（在 nuget 引用的项目文件中）有效

<PackageReference Include="Microsoft.EntityFrameworkCore" Version="2.1.8" />
<PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="2.1.8" />

而那些，没有：

<PackageReference Include="Microsoft.EntityFrameworkCore" Version="2.2.0" />
<PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="2.2.0" />

<PackageReference Include="Microsoft.EntityFrameworkCore" Version="2.2.0" />
<PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="2.1.8" />