Linq 集合操作

阿新發表於2017-02-13

Linq 集合操作

演示程式碼

兩個物件一個是Person,一個Address, AddressId是外來鍵,

public class Person

{

public string ID { get; set; }

public string Name { get; set; }

public int Age { get; set; }

public double Salary { get; set; }

public DateTime Born { get; set; }

public int IdAddress { get; set; }

}

 

public class Address

{

public int IdAddress { get; set; }

public string Street { get; set; }

public int Num { get; set; }

public string City { get; set; }

}

  

 

測試資料如下

Person類

Address類

下面我會用7個方式實現7中集合操作

  1. INNER JOIN 內連結
  2. LEFT JOIN 左連線
  3. RIGHT JOIN 右連結
  4. FULL OUTER JOIN 所有
  5. LEFT JOIN EXCLUDING INNER JOIN 左空
  6. RIGHT JOIN EXCLUDING INNER JOIN 右空
  7. FULL OUTER JOIN EXCLUDING INNER JOIN ??

    學校數學沒學好不知道專業術語!哈哈

    INNER JOIN  

    最常用的方法,兩表關聯查詢

    標準Linq語法

    var result = from p in Person.BuiltPersons()
    
    join a in Address.BuiltAddresses()
    
    on p.IdAddress equals a.IdAddress
    
    select new
    
         {
    
    Name = a.MyPerson.Name,
    
    Age = a.MyPerson.Age,
    
    PersonIdAddress = a.MyPerson.IdAddress,
    
    AddressIdAddress = a.MyAddress.IdAddress,
    
    Street = a.MyAddress.Street
    
         };
    

      

    Lambda Expression: 

    var resultJoint = Person.BuiltPersons().Join( /// Source Collection
    
    Address.BuiltAddresses(), /// Inner Collection
    
    p => p.IdAddress, /// PK
    
    a => a.IdAddress, /// FK
    
    (p, a) => new { MyPerson = p, MyAddress = a }) /// Result Collection
    
    .Select(a => new
    
    {
    
    Name = a.MyPerson.Name,
    
    Age = a.MyPerson.Age,
    
    PersonIdAddress = a.MyPerson.IdAddress,
    
    AddressIdAddress = a.MyAddress.IdAddress,
    
    Street = a.MyAddress.Street
    
    });
    

      

     

    Lambda表示式主要有5部分

  8. Is the main Collection. 
  9. Is the inner Collection.
  10. Is the PK.
  11. Is the FK.
  12. Is the type for the result collection. 

    查詢結果如下

    LEFT JOIN

    新增一個LeftJoin的擴充套件方法

    public static IEnumerable<TResult>
    
        LeftJoin<TSource, TInner, TKey, TResult>(this IEnumerable<TSource> source,
    
    IEnumerable<TInner> inner,
    
    Func<TSource, TKey> pk,
    
    Func<TInner, TKey> fk,
    
    Func<TSource, TInner, TResult> result)
    
    {
    
    IEnumerable<TResult> _result = Enumerable.Empty<TResult>();
    
     
    
    _result = from s in source
    
    join i in inner
    
    on pk(s) equals fk(i) into joinData
    
    from left in joinData.DefaultIfEmpty()
    
    select result(s, left);
    
     
    
    return _result;
    
    }
    

      

     Lambda Expression: 

    var resultJoint = Person.BuiltPersons().LeftJoin( /// Source Collection
    
    Address.BuiltAddresses(), /// Inner Collection
    
    p => p.IdAddress, /// PK
    
    a => a.IdAddress, /// FK
    
    (p, a) => new { MyPerson = p, MyAddress = a }) /// Result Collection
    
    .Select(a => new
    
    {
    
    Name = a.MyPerson.Name,
    
    Age = a.MyPerson.Age,
    
    PersonIdAddress = a.MyPerson.IdAddress,
    
    AddressIdAddress = (a.MyAddress != null ? a.MyAddress.IdAddress : -1),
    
                Street = (a.MyAddress != null ? a.MyAddress.Street : "Null-Value")
    
    });
    

      

    注意:如果address為空Null需要做一個替換,否則會報錯

    查詢結果如下

    RIGHT JOIN 

    Extension Method: 

    public static IEnumerable<TResult>
    
        RightJoin<TSource, TInner, TKey, TResult>(this IEnumerable<TSource> source,
    
    IEnumerable<TInner> inner,
    
    Func<TSource, TKey> pk,
    
    Func<TInner, TKey> fk,
    
    Func<TSource, TInner, TResult> result)
    
    {
    
    IEnumerable<TResult> _result = Enumerable.Empty<TResult>();
    
     
    
    _result = from i in inner
    
    join s in source
    
    on fk(i) equals pk(s) into joinData
    
    from right in joinData.DefaultIfEmpty()
    
    select result(right, i);
    
     
    
    return _result;
    
    }
    

      

       

     Lambda Expression: 

    var resultJoint = Person.BuiltPersons().RightJoin( /// Source Collection
    
    Address.BuiltAddresses(), /// Inner Collection
    
    p => p.IdAddress, /// PK
    
    a => a.IdAddress, /// FK
    
    (p, a) => new { MyPerson = p, MyAddress = a }) /// Result Collection
    
    .Select(a => new
    
    {
    
    Name = (a.MyPerson != null ? a.MyPerson.Name : "Null-Value"),
    
    Age = (a.MyPerson != null ? a.MyPerson.Age : -1),
    
    PersonIdAddress = (a.MyPerson != null ? a.MyPerson.IdAddress : -1),
    
    AddressIdAddress = a.MyAddress.IdAddress,
    
    Street = a.MyAddress.Street
    
    });
    

      

     

     

    查詢結果如下

    FULL OUTER JOIN 

    Extension Method: 

    public static IEnumerable<TResult>
    
        FullOuterJoinJoin<TSource, TInner, TKey, TResult>(this IEnumerable<TSource> source,
    
    IEnumerable<TInner> inner,
    
    Func<TSource, TKey> pk,
    
    Func<TInner, TKey> fk,
    
    Func<TSource, TInner, TResult> result)
    
    {
    
     
    
    var left = source.LeftJoin(inner, pk, fk, result).ToList();
    
    var right = source.RightJoin(inner, pk, fk, result).ToList();
    
     
    
    return left.Union(right);
    
    }
    

      

     Lambda Expression: 

    var resultJoint = Person.BuiltPersons().FullOuterJoinJoin( /// Source Collection
    
    Address.BuiltAddresses(), /// Inner Collection
    
    p => p.IdAddress, /// PK
    
    a => a.IdAddress, /// FK
    
    (p, a) => new { MyPerson = p, MyAddress = a }) /// Result Collection
    
    .Select(a => new
    
    {
    
    Name = (a.MyPerson != null ? a.MyPerson.Name : "Null-Value"),
    
    Age = (a.MyPerson != null ? a.MyPerson.Age : -1),
    
    PersonIdAddress = (a.MyPerson != null ? a.MyPerson.IdAddress : -1),
    
    AddressIdAddress = (a.MyAddress != null ? a.MyAddress.IdAddress : -1),
    
    Street = (a.MyAddress != null ? a.MyAddress.Street : "Null-Value")
    
    });
    

      

     

    注意:每個物件都需要驗證Null

    查詢結果如下

    LEFT EXCLUDING JOIN 

    Extension Method: 

    public static IEnumerable<TResult>
    
        LeftExcludingJoin<TSource, TInner, TKey, TResult>(this IEnumerable<TSource> source,
    
    IEnumerable<TInner> inner,
    
    Func<TSource, TKey> pk,
    
    Func<TInner, TKey> fk,
    
    Func<TSource, TInner, TResult> result)
    
    {
    
    IEnumerable<TResult> _result = Enumerable.Empty<TResult>();
    
     
    
    _result = from s in source
    
    join i in inner
    
    on pk(s) equals fk(i) into joinData
    
    from left in joinData.DefaultIfEmpty()
    
    where left == null
    
    select result(s, left);
    
     
    
    return _result;
    
    }
    

      

     Lambda Expression:  

    var resultJoint = Person.BuiltPersons().LeftExcludingJoin( /// Source Collection
    
    Address.BuiltAddresses(), /// Inner Collection
    
    p => p.IdAddress, /// PK
    
    a => a.IdAddress, /// FK
    
    (p, a) => new { MyPerson = p, MyAddress = a }) /// Result Collection
    
    .Select(a => new
    
    {
    
    Name = a.MyPerson.Name,
    
    Age = a.MyPerson.Age,
    
    PersonIdAddress = a.MyPerson.IdAddress,
    
    AddressIdAddress = (a.MyAddress != null ? a.MyAddress.IdAddress : -1),
    
    Street = (a.MyAddress != null ? a.MyAddress.Street : "Null-Value")
    
    });
    

      

    查詢結果如下

    RIGHT EXCLUDING JOIN

    Extension Method:  

    public static IEnumerable<TResult>
    
    RightExcludingJoin<TSource, TInner, TKey, TResult>(this IEnumerable<TSource> source,
    
    IEnumerable<TInner> inner,
    
    Func<TSource, TKey> pk,
    
    Func<TInner, TKey> fk,
    
    Func<TSource, TInner, TResult> result)
    
    {
    
    IEnumerable<TResult> _result = Enumerable.Empty<TResult>();
    
     
    
    _result = from i in inner
    
    join s in source
    
    on fk(i) equals pk(s) into joinData
    
    from right in joinData.DefaultIfEmpty()
    
    where right == null
    
    select result(right, i);
    
     
    
    return _result;
    
    }
    

      

     Lambda Expression:   

    var resultJoint = Person.BuiltPersons().RightExcludingJoin( /// Source Collection
    
    Address.BuiltAddresses(), /// Inner Collection
    
    p => p.IdAddress, /// PK
    
    a => a.IdAddress, /// FK
    
    (p, a) => new { MyPerson = p, MyAddress = a }) /// Result Collection
    
    .Select(a => new
    
    {
    
    Name = (a.MyPerson != null ? a.MyPerson.Name : "Null-Value"),
    
    Age = (a.MyPerson != null ? a.MyPerson.Age : -1),
    
    PersonIdAddress = (a.MyPerson != null ? a.MyPerson.IdAddress : -1),
    
    AddressIdAddress = a.MyAddress.IdAddress,
    
    Street = a.MyAddress.Street
    
    });
    

      

     

    查詢結果

    FULL OUTER EXCLUDING JOIN  

    Extension Method:  

    public static IEnumerable<TResult>
    
    FulltExcludingJoin<TSource, TInner, TKey, TResult>(this IEnumerable<TSource> source,
    
    IEnumerable<TInner> inner,
    
    Func<TSource, TKey> pk,
    
    Func<TInner, TKey> fk,
    
    Func<TSource, TInner, TResult> result)
    
    {
    
    var left = source.LeftExcludingJoin(inner, pk, fk, result).ToList();
    
    var right = source.RightExcludingJoin(inner, pk, fk, result).ToList();
    
     
    
    return left.Union(right);
    
    }
    

      

     Lambda Expression:   

    var resultJoint = Person.BuiltPersons().FulltExcludingJoin( /// Source Collection
    
    Address.BuiltAddresses(), /// Inner Collection
    
    p => p.IdAddress, /// PK
    
    a => a.IdAddress, /// FK
    
    (p, a) => new { MyPerson = p, MyAddress = a }) /// Result Collection
    
    .Select(a => new
    
    {
    
    Name = (a.MyPerson != null ? a.MyPerson.Name : "Null-Value"),
    
    Age = (a.MyPerson != null ? a.MyPerson.Age : -1),
    
    PersonIdAddress = (a.MyPerson != null ? a.MyPerson.IdAddress : -1),
    
    AddressIdAddress = (a.MyAddress != null ? a.MyAddress.IdAddress : -1),
    
    Street = (a.MyAddress != null ? a.MyAddress.Street : "Null-Value")
    
    });
    

      

     

    查詢結果

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