Question

F＃。我有以下类型的列表transactions：

type Transaction(Debitor: string, Spend:float, Creditor:string)  = 
     member this.Debitor = Debitor
     member this.Spend = Spend
     member this.Creditor = Creditor

我知道如何按一个值分组。举例来说，我想按属性Debitor进行分组，可以轻松地将该属性用作该组的键：

let tsGroupDebitor =
    transactions        
    |> Seq.groupBy(fun ts -> ts.Debitor)

但是，我无法按两个值分组，例如Debitor和Creditor。理想情况下，我想为Debitor属性应用聚合函数“ Sum”的同时考虑Creditor和Spend。

换句话说，我想实现与以下LINQ查询等效的F＃：

 var transactions_GroupSameDebitorCreditor = 
     transactions
     .GroupBy(ts => new { ts.Debitor, ts.Creditor }) // group by multiple values
     .Select(gr => new 
            {
                Debitor = gr.Key.Debitor,
                Debit = gr.Sum(trans => trans.Spend), //sum the trans values per grouped relationships
                Creditor = gr.Key.Creditor
            });

返回匿名类型的IEnumerable。

Answer 1

您可以像这样使用元组作为组键：

let tsGroupDebitor =
    transactions        
    |> Seq.groupBy(fun ts -> (ts.Debitor, ts.Creditor))

如果您想汇总每个组的交易以汇总Spend属性，则可以这样做：

let tsGroupDebitor =
        transactions        
        |> Seq.groupBy(fun ts -> (ts.Debitor, ts.Creditor))
        |> Seq.map(fun ((debitor, creditor), values) -> ( debitor, creditor, values |> Seq.sumBy (fun t -> t.Spend)))

请注意如何将模式匹配与模式((debitor, creditor), values)配合使用，以便能够访问组密钥的两个部分以及每个组（values）的交易顺序

Answer 2

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        }

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        {
            MessageBox.Show(ex.Message);
        }

        finally
        {
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        }
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F＃通过多个值进行分组并汇总

2 个答案: