LINQ full out join 实现

今天在CSDN上看到一网友提问，问题大意如下：

 

比如dt1数据是
id price
1 100
2 100

dt2
id excelprice
1 100
3 200

想要得出来的数据是:
id price excleprice
1 100 100
2 100 null
3 null 100

 

如何实现？

首先想到的实现方式是：

 

void Main()
{
    DataTable dtA = new DataTable();
        dtA.Columns.Add("id", typeof(int));
        dtA.Columns.Add("price", typeof(string));
        dtA.Rows.Add(1, "100");
        dtA.Rows.Add(2, "100");
     
    DataTable dtB = dtA.Clone();
        dtB.Rows.Add(1, "100"); 
        dtB.Rows.Add(3, "100");
 
    DataTable dtC = dtA.Clone();
        dtC.Columns.Add("price_excel");
  var fullJoinData =(from a in dtA.AsEnumerable()
                    join b in dtB.AsEnumerable()
                    on a.Field<int>("id") equals b.Field<int>("id") into g
                    from b in g.DefaultIfEmpty()
                    select new
                    {
                        id = a.Field<int>("id"),
                        price = a.Field<string>("price"),
                        price_excel = b == null ? "Null" : b.Field<string>("price")
                    }).Union
                    (
                        from  b in dtB.AsEnumerable()
                        join a in dtA.AsEnumerable()
                        on b.Field<int>("id") equals a.Field<int>("id") into g
                        from a in g.DefaultIfEmpty()
                        select new
                        {
                            id = b.Field<int>("id"),
                            price = a == null ? "Null" : a.Field<string>("price"),
                            price_excel =b.Field<string>("price") 
                        }
                    );
                    
 fullJoinData.ToList().ForEach(q => dtC.Rows.Add(q.id, q.price, q.price_excel));
 }

 

后来写了一个条理比较清晰的实现方式：

 

void Main()
{
    DataTable dtA = new DataTable();
        dtA.Columns.Add("id", typeof(int));
        dtA.Columns.Add("price", typeof(string));
        dtA.Rows.Add(1, "100");
        dtA.Rows.Add(2, "100");
     
    DataTable dtB = dtA.Clone();
        dtB.Rows.Add(1, "100"); 
        dtB.Rows.Add(3, "100");
 
    DataTable dtC = dtA.Clone();
        dtC.Columns.Add("price_excel");
        
    var leftData=from a in dtA.AsEnumerable()
                    join b in dtB.AsEnumerable()
                    on a.Field<int>("id") equals b.Field<int>("id") into g
                    from b in g.DefaultIfEmpty()
                    select new
                    {
                        id = a.Field<int>("id"),
                        price = a.Field<string>("price"),
                        price_excel = b == null ? "Null" : b.Field<string>("price")
                    };
    var rightData=from b in dtB.AsEnumerable()
                  where  !dtA.AsEnumerable().Select(a=>a.Field<int>("id")).Contains(b.Field<int>("id"))
                  select new 
                    {
                            id = b.Field<int>("id"),
                            price = "Null",
                            price_excel =b.Field<string>("price") 
                    };
        
 var fullJoinData =leftData.Union(rightData);
 fullJoinData.ToList().ForEach(q => dtC.Rows.Add(q.id, q.price, q.price_excel));

}

 

 

原问题地址:http://topic.csdn.net/u/20120221/10/6e7691f8-00bf-44a1-9e52-90bad0bbc416.html?seed=93059827&r=77628090#r_77628090