我不明白这个错误..我认为据我所知有一个数据类型，但我不明白怎么做？答案

【问题标题】：I dont understand the error.. I think as far as I know there is a dataType, but I dont see how?我不明白这个错误..我认为据我所知有一个数据类型，但我不明白怎么做？
【发布时间】：2018-10-12 12:09:10
【问题描述】：

在下面的代码中，我希望我能正确地指出什么是错的。我需要能够调用 item.departments.dept_Type 并且这应该是可能的，因为我已经建立了关联。如果我理解正确，我不需要在查询上创建内部联接来获取数据。这是我的 PersonClass

    namespace DATALAYER.DataHandler
{

    [Table(Name = "People")]

        public class Person 
        {


        private int _DepartmentID;
        public EntityRef<Department> _Department;
        public Person() { this._Department = new EntityRef<Department>(); }
        private int _ID;
            [Column(IsPrimaryKey =true, Storage ="_ID")]
            public int ID
            {
                get { return this._ID; }
                set { this._ID = value; }
            }
            private string _p_FirstName;
            [Column(Storage = "_p_FirstName")]
            public string p_FirstName
            {
                get { return this._p_FirstName; }
                set { this._p_FirstName = value; }
            }
            private string _LastName;
            [Column(Storage = "_LastName")]
            public string p_LastName
            {
                get { return this._LastName; }
                set { this._LastName = value; }
            }
            private string _EmailAddress;
            [Column(Storage = "_EmailAddress")]
            public string p_EmailAddress
            {
                get { return this._EmailAddress; }
                set { this._EmailAddress = value; }
            }
            private string _Password;
            [Column(Storage = "_Password")]
            public string p_Password
            {
                get { return this._Password; }
                set { this._Password = value; }
            }
            private string _SSID;
            [Column(Storage = "_SSID")]
            public string p_SSID
            {
                get { return this._SSID; }
                set { this._SSID = value; }
            }
            private string _DOB;
            [Column(Storage = "_DOB")]
            public string p_DOB
            {
                get { return this._DOB; }
                set { this._DOB = value; }
            }
            private string _CellNumber;
            [Column(Storage = "_CellNumber")]
            public string p_CellNumber
            {
                get { return this._CellNumber; }
                set { this._CellNumber = value; }
            }

            [Column(Storage = "_DepartmentID", DbType = "Int")]
            public int p_Department_dept_ID
            {
                get { return this._DepartmentID; }
                set { this._DepartmentID = value; }
            }

            [Association(Storage = "_DepartmentID", ThisKey = "p_Department_dept_ID")]
            public Department Department
            {
                get { return this._Department.Entity; }
                set { this._Department.Entity = value; }
            }
    }

}

这是我的部门代码

    namespace DATALAYER.DataHandler
{
    [Table(Name = "Departments")]
    public class Department
    {
        //private EntitySet<Person> _Person;
        //public Department()
        //{
        //    this._Person = new EntitySet<Person>();
        //}
        private int _DepartmentID;
        [Column(IsPrimaryKey = true, Storage = "_DepartmentID")]
        public int dept_ID
        {
            get { return this._DepartmentID; }
            set { this._DepartmentID = value; }

        }
        private string _deptType;
        [Column(Storage = "_deptType")]
        public string dept_Type
        {
            get { return this._deptType; }
            set { this._deptType = value; }
        }
        //[Association(Storage = "_Person", OtherKey = "ID")]
        //public EntitySet<Person> Persons
        //{
        //    get { return this._Person; }
        //    set { this._Person.Assign(value); }
        //}

    }
}

现在我在想的问题是人员的主键和部门的外键之间的数据类型存在问题。但由于他们都是 int 我不明白这怎么会是个问题。

如果有人可以解释我的问题，如果我错了或什么，或者帮助我解决问题，请。

添加了这个类

namespace DATALAYER.DataHandler
{
public class SHSdb2 : DataContext
{
    public Table<Person> People;
    public Table<Department> Department;
    //public Table<Address> Address;
    public SHSdb2(string connection) : base(connection) { }
}

} 人表部门表

没有这个代码它可以工作，但我只能调用表格内的东西

        [Column(Storage = "_DepartmentID", DbType = "Int")]
    public int p_Department_dept_ID
    {
        get { return this._DepartmentID; }
        set { this._DepartmentID = value; }
    }

    [Association(Storage = "_DepartmentID", ThisKey = "p_Department_dept_ID")]
    public Department Department
    {
        get { return this._Department.Entity; }
        set { this._Department.Entity = value; }
    }

【问题讨论】：

单步执行代码时会发生什么？它实际上在哪里失败了？
什么是SHSdb2？您真的在使用 LINQ to SQL 吗？或者也许是实体框架？
当它进入foreach时
SHSdb2 是我的项目名称，不允许使用实体框架，这就是我使用这种 Linq 映射方法的原因
添加了另一个类可能会有所帮助。不确定最小、竞争和可验证的示例。如果你复制过去，你可能只需要数据库，它应该可以工作......我认为。

标签： c# sql-server linq-to-sql mapping

【解决方案1】：

似乎我用这个修复了它，不确定它是否可以修复，或者我很幸运，如果有人仍然可以向我解释这一点，我将不胜感激。

var personQuery =
            from per in db.People
            where per.p_FirstName == "Christian" 
            select per.Department;

我正在考虑指定它需要从允许它在 foreach 中获取的部门获取数据。

【讨论】：