C#, LINQ, 利用group new 來取得多欄位group by

void Main()
{
	// 建立 ClassA 的 List
	List<ClassA> classAList = new List<ClassA>
		{
			new ClassA("A1", 10),
			new ClassA("A2", 20),
			new ClassA("A3", 30),
			new ClassA("A1", 15),
			new ClassA("A2", 25),
			new ClassA("A3", 35)
		};
	// 建立 ClassB 的 List
	List<ClassB> classBList = new List<ClassB>
		{
			new ClassB("A1", "C1"),
			new ClassB("A2", "C2")
		};
	//classAList.Dump();
	//classBList.Dump();
	// 使用 LINQ 進行關聯和分組
	var query = from a in classAList
				join b in classBList on a.A equals b.A
				select a;
    query.Dump();				
				
	var query2 = from a in query
				group new { a.A, a.B } by a.A into grouped
				select new { A = grouped.Key, SumB = grouped.Sum(item => item.B) };
	query2.Dump();                  
				
				
}
// Define other methods and classes here
// ClassA 定義
class ClassA
{
	public string A { get; set; }
	public int B { get; set; }
	public ClassA(string a, int b)
	{
		A = a;
		B = b;
	}
}
// ClassB 定義
class ClassB
{
	public string A { get; set; }
	public string C { get; set; }
	public ClassB(string a, string c)
	{
		A = a;
		C = c;
	}
}

 

執行結果 :

A B
A1 10
A2 20
A1 15
A2 25

A SumB
A1 25
A2 45