[英]How do I extract and combine a list of n lists?
我有一個列表,它本身包含n個列表(在這種情況下,有4個)。 我需要做的是獲取輸出,如下面的“必需的查詢結果”所示
清單清單:
Product Year DY
Comp 1992 110.0
Comp 1993 200.0
Non-Comp 1990 45.2
Non-Comp 1991 50.0
Non-Comp 1992 55.0
Non-Comp 1993 100.0
Product Year DY
Comp 1992 170.0
Non-Comp 1990 64.8
Non-Comp 1991 75.0
Non-Comp 1992 85.0
Product Year DY
Non-Comp 1991 25.0
Product Year DY
Non-Comp 1990 37.0
所需查詢結果:
Product Year DY1 DY2 DY3 DY4
Comp 1992 110.0 170.0
Comp 1993 200.0
Non-Comp 1990 45.2 64.8 37.0
Non-Comp 1991 50.0 75.0 25.0
Non-Comp 1992 55.0 85.0
Non-Comp 1993 100.0
請記住,列表中可能有4個以上的列表,所以我想到了類似的東西:
foreach (var element in myList)
{
// some hard work
}
如果沒有更好地描述輸入/輸出對象模型,很難回答這個問題,但是我想您要:
就像是:
var query = myListOfLists.SelectMany(list => list) // Flatten
.GroupBy(item => new { item.Product, item.Year }, // Group
item => item.DY); // Project
像這樣嗎
List<List<Product>> nestedList;
List<Product> = allProducts = nestedList.SelectMany(x => x);
var groupped = allProducts
.GroupBy(x => new { Product = x.Product, Year = x.Year}, x => x.DY );
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