Linq Join，按多个字段分组

Question

我有两个table如下

public class Customer
{
    public string Id{ get; set; }
    public string Name { get; set; }

    [DataType(DataType.Currency), Column(TypeName = "decimal(18,2)")]
    public decimal Balance { get; set; }

    [Display(Name ="Time Registered")]
    public DateTime TimeRegistered { get; set; }

    [InverseProperty("Beneficiary")]
    public ICollection<WalletTransaction> TransactionsReceived { get; set; }

    [InverseProperty("Sender")]
    public ICollection<WalletTransaction> TransactionsInitiated { get; set; }
}

和

public class WalletTransaction
{
    public int Id { get; set; }

    public TransactionType TrasactionType { get; set; }

    public decimal Amount { get; set; }

    public string SenderId { get; set; }

    public string ReceipientId { get; set; }

    [ForeignKey("SenderId")]
    public Customer Sender { get; set; }

    [ForeignKey("ReceipientId")]
    public Customer Beneficiary { get; set; }
}

和交易类型可以在以下枚举中

public enum TransactionType
{
    Deposit=1,Transfer=2,Withdrawal=3
}

现在我需要获取每个客户交易的摘要，细分为不同的交易类型，如下所示：

Name of CustomerA
    Deposit=Sum of the amount value in all his transactions of transaction type Deposit
    Transfer=Sum of the amount value in all his transactions of transaction type Transfer
    Withdrawal=Sum of the amount value in all his transactions of transaction type Withdrawal
Name of CustomerB
    Deposit=Sum of the amount value in all his transactions of transaction type Deposit
    Transfer=Sum of the amount value in all his transactions of transaction type Transfer
    Withdrawal=Sum of the amount value in all his transactions of transaction type Withdrawal
Name of CustomerC
    Deposit=Sum of the amount value in all his transactions of transaction type Deposit
    Transfer=Sum of the amount value in all his transactions of transaction type Transfer
    Withdrawal=Sum of the amount value in all his transactions of transaction type Withdrawal
etc.

我不知道如何实现我的想法是我需要创建 linq 查询来加入客户 table 和交易 table 以从客户 table 中获取客户的姓名。然后，按客户和交易类型对交易进行分组。我不确定这是否正确，但即使是这样，我也不知道该怎么做。

我试过这样做

var customerTransactions = await _context.Customers
            .Include(c => c.TransactionsInitiated)
            .Select(a => new
            {
                //Looking for how to break down he transactions by the transaction types here
            })
            .OrderByDescending(s=>s.TotalAmount)//Not sure too how to order the result
            .ToListAsync();

请指导我如何解决这些问题。谢谢

Answer 1

由于您具有导航属性，因此在 LINQ 语句中不需要 Join。基本上你想要的可以在

这样的查询中完成

_context.Customers
.Select(a => new
{
    c.Name,
    Deposit = c.TransactionsInitiated
        .Where(t => t.TransactionType == TransactionType.Deposit).Sum(t => t.Amount),
    Transfer = c.TransactionsInitiated
        .Where(t => t.TransactionType == TransactionType.Transfer).Sum(t => t.Amount),
    Withdrawal = c.TransactionsInitiated
        .Where(t => t.TransactionType == TransactionType.Withdrawal).Sum(t => t.Amount),
    TotalAmount = c.TransactionsInitiated
        .Sum(t => t.Amount),
})
.OrderByDescending(s => s.TotalAmount)

...并且 EF 将加入生成的 SQL 语句。

免责声明：EF 核心 3 在将更复杂的查询转换为 SQL 方面非常有限，我不确定这是否真的有效，而且我手头没有类似的测试用例。

Linq Join，按多个字段分组

Linq Join, group by multiple field

c#

linq

asp.net-core-3.1

ef-core-3.1