求 linq to sql 的select 功能的实现

Question

在数据库中有一张表CREATE TABLE [dbo].[Table_Temp](
[Row_A] [nvarchar](50) NOT NULL,
[Row_B] [int] NOT NULL
) 在 linq to sql  中  对应的 dbml 文件片断如下.
[Table(Name="dbo.Table_Temp")]
public partial class Table_Temp
{

private string _Row_A;

private int _Row_B;

public Table_Temp()
{
}

[Column(Storage="_Row_A", DbType="NVarChar(50) NOT NULL", CanBeNull=false)]
public string Row_A
{
get
{
return this._Row_A;
}
set
{
if ((this._Row_A != value))
{
this._Row_A = value;
}
}
}

[Column(Storage="_Row_B", DbType="Int NOT NULL")]
public int Row_B
{
get
{
return this._Row_B;
}
set
{
if ((this._Row_B != value))
{
this._Row_B = value;
}
}
}
}当在 程序中 使用 以下代码 查询数据时
            using (Dc_Cotext dbContext = new Dc_Cotext ())
            {
              List<string> temp = dbContext.Table_Temps.Select(p => p.Row_A).ToList();
            }
生成的 sql 如下:SELECT [t0].[Row_A]
FROM [dbo].[Table_Temp] AS [t0]我现在的问题是 如何 从 select 的参数  p => p.Row_A   得到  需要的字符串 即 我 输入   p => p.Row_A  时           返回的是  " [Row_A]"  这个字符串
 输入   p => p.Row_B  时           返回的是  " [Row_B]"  这个字符串
根了一下代码 发现 select 的定义如下：public static IQueryable<TResult> Select<TSource, TResult>(this IQueryable<TSource> source, Expression<Func<TSource, TResult>> selector);其参数是一个 基于 lamda 表达式的  表达式树即如何 通过输入的  lamda 表达式  得到我想要的  字符串

Answer 1

学习以下，怎么查看到这个sql的：SELECT [t0].[Row_A]
FROM [dbo].[Table_Temp] AS [t0] ？？？

Answer 2

是不是应该是这样的var temp = from r in dbContext.Table_Temps
                     select r.Row_A

Answer 3

class Program 
    { 
        private static List <Student> GetStudents() 
        { 
            List <Student> students = new List <Student> { 
            new Student{ Name="YOUNG", Age=25, Language="Chinese"}, 
            new Student{ Name="JESSIE", Age=21, Language="Scotland"}, 
            new Student{ Name="KELLY", Age=18, Language="English"}, 
            new Student{ Name="JUNE", Age=20, Language="English"}, 
            new Student{ Name="ADRIAN", Age=22, Language="Italy"}, 
            new Student{ Name="BRUCE", Age=17, Language="Scotland"}, 
            new Student{ Name="BRANT", Age=30, Language="Germany"}, 
            new Student{ Name="BEN", Age=25, Language="Chinese"} 
            }; 
            return students;         }         static void Main(string[] args) 
        { 
            List <Student> studentList = GetStudents();             Select(studentList); 
        }         private static void Select <T>(T studentList) 
        { 
            OnlySearch(studentList); 
            SearchCollectChangeOtherCollect(studentList); 
            BuilderAnomy(); 
            BuilderAnomyExter(); 
            SelectLambda(); 
            ComplexSelect(); 
            ComplexSelectLambda(); 
        }         private static void OnlySearch <T>(T studentList) 
        { 
            Console.WriteLine(" <hr>只查询合适对象集合的某个属性： <br>");             //lamb的写法 
            var students = RevealChangeType(studentList).Where(n=>n.Language == "Chinese").Select(n=>n.Name);             //linq的写法 
            //var students = from n in RevealChangeType(studentList) 
            //              where n.Language == "Chinese" 
            //              select n.Name;             foreach (var student in students) 
            { 
                Console.WriteLine(string.Format(" <span class='result'>{0} </span>", student)); 
            } 
        }         private static IEnumerable <Student> RevealChangeType <T>(T obj) 
        { 
            IEnumerable <Student> student = obj as IEnumerable <Student>;             return student; 
        }         private static void SearchCollectChangeOtherCollect <T>(T obj) 
        { 
            Console.WriteLine(" <hr>从一个集合中查询，转化到另外一个集合： <br>");             //age Array 
            int[] intArray ={ 25, 1, 4, 3 };             //lamb的写法 
            var students = intArray.SelectMany(n=>RevealChangeType(obj).Where(s=>s.Age == n));             //linq的写法 
            //var students = from s in RevealChangeType(obj) 
            //              from n in intArray 
            //              where s.Age == n 
            //              select s;             foreach (var student in students) 
            { 
                Console.WriteLine(string.Format(" <span class='result'>{0} </span>", student.Name)); 
            } 
        }         private static void BuilderAnomy() 
        { 
            Console.WriteLine(" <hr>构建匿名类型： <br>");             List <Student> studentList = GetStudents(); 
            int[] intArray = { 3, 1, 6, 4 };             //lamb的写法 
            var stu = intArray.Select(n=>new { Id = n, Name = (studentList as List <Student>)[n].Name });             //linq的写法 
            //var stu = from n in intArray 
            //          select  new{Id = n,Name=(studentList as List <Student>)[n].Name};             foreach (var s in stu) 
            { 
                Console.WriteLine(string.Format(" <div class='result'>id:{0};name:{1} </div>", s.Id, s.Name)); 
            } 
        }         private static void BuilderAnomyExter() 
        { 
            Console.WriteLine(" <hr>构建匿名类型2——扩展已有类： <br>");             List <Student> studentList = GetStudents(); 
            int[] intArray = { 3, 1, 6, 4 };             //lamb的写法 
            var students = intArray.Select(n=>new { Id = n, studentList[n].Name, studentList[n].Age });             //linq的写法 
            //var students = from n in intArray 
            //              select new {Id = n, studentList[n].Name, studentList[n].Age};             foreach (var student in students) 
            { 
                Console.WriteLine(string.Format(" <div class='result'>id:{0}; name:{1}; age:{2} </div>", student.Id, student.Name, student.Age)); 
            } 
        }         private static void SelectLambda() 
        { 
            Console.WriteLine(" <hr>select的Lambda表达式： <br>");             List <Student> studentList = GetStudents(); 
            int[] intArray = { 3, 1, 6, 4 };             //lamb的写法 
            var stu = intArray.Select(i=>new { Id = i, studentList[i].Name });             //linq的写法 
            //var stu = from i in intArray 
            //          select new {Id = i, studentList[i].Name};             foreach (var student in stu) 
            { 
                Console.WriteLine(string.Format(" <div class='result'>id:{0}; name:{1} </div>", student.Id, student.Name)); 
            } 
        }         private static void ComplexSelect() 
        { 
            Console.WriteLine(" <hr>复合选择： <br>");             List <Student> studentList = GetStudents(); 
            string[] stringArray = { "Ajax", "Csharp", "Javascript", "Css Desige", "Asp.net", "Gis" };             //lamb的写法 
            //var stu = stringArray.Where(s=>s.Length > 8).SelectMany(s=>studentList.Where(str1=>str1.Age > 23).Select(str=>new { book = s, name = str.Name })); 
            var stu = studentList.Where(sl=>sl.Age > 23).SelectMany(sl=>stringArray.Where(s=>s.Length > 8).Select(s=>new { name = sl.Name, book = s }));             //linq的写法 
            //var stu = from sl in studentList 
            //          where sl.Age > 23 
            //          from s in stringArray 
            //          where s.Length > 8 
            //          select new {name = sl.Name, book = s};             foreach (var student in stu) 
            { 
                Console.WriteLine(string.Format(" <div class='result'>{0} is studying {1} </div>", student.name, student.book)); 
            } 
        }         private static void ComplexSelectLambda() 
        { 
            Console.WriteLine(" <hr>多重选择的Lambda表达式： <br>");             List <Student> studentList = GetStudents(); 
            string[] stringArray = { "Ajax", "Csharp", "Javascript", "Css Desige", "Asp.net", "Gis" };             //lamb的写法 
            //var stu = studentList.SelectMany(s=>stringArray.Select(str => s.Name + "has a book names " + str));             //linq的写法 
            var stu = from sl in studentList                    
                      from s in stringArray                      
                      select new {name=sl.Name,language=s};             foreach (var s in stu) 
            { 
                Console.WriteLine(string.Format(" <div class='result'>{0} </div>", s)); 
            } 
        } 
    }     sealed class Student 
    { 
        public int age; 
        public int Age 
        { 
            get { return age; } 
            set { age = value; } 
        }         private string name; 
        public string Name 
        { 
            get { return name; } 
            set { name = value; } 
        }         private string language; 
        public string Language 
        { 
            get { return language; } 
            set { language = value; } 
        } 
    } ------ select top * from table 语法补充--------skip(index).Take(count)     varResults=fromdtinctx.Customers.Skip(0).Take(10)1.Top 查询－－－－skip(index).Take(count)
     var Results = from dt in ctx.Customers.Skip(0).Take(10)
                             select new
                             ...{
                                 dt.CustomerID,
                                 dt.CompanyName,
                                 dt.City
                             };
   2.Like 查询－－－－startwith()
              from dt in ctx.Customers
              where dt.ID.Startwith('A')
   3.In查询－－－－Contain()
     string[] s = ...{ "ivan","aaa","aaaa"};
               var Results = from dt in ctx.Customers.Skip(0).Take(10)
                             where s.Contains(dt.CustomerID)
                             select new
                             ...{
                                 dt.CustomerID,
                                 dt.CompanyName,
                                 dt.City
                             };

Answer 4

NorthwindDataContext db = new NorthwindDataContext();
 public IQueryable<Employees> GetList(string strCity)
  {
      return from p in db.Employees
            where p.City == strCity
            select p;
   }
参考
参考 

Answer 5

谢谢大家, 最终通过 lamda表达式结合相关的字符串处理达到目的
        public static List<T> sample<Result>(Expression<Func<T, Result>> I_Field)
        {
            Sql_QueryNode<T> R_Result = new Sql_QueryNode<T>();            string filed = I_Field.Body.ToString();
            filed = filed.Substring(filed.IndexOf('.') + 1);
................................................
................................................
................................................
 }