假設我有一個名為CustomerTransaction的表，我可以將選擇條件傳遞給類似void GetData1(Expression<Func<CustomerTransaction, bool>> selection){ CustomerTransaction.Where(selection).Take(2).Dump();}使用類似的代碼Expression<Func<CustomerTransaction, bool>> query = r => (r.CustomerID == 1);GetData1(query);但是，我希望能夠聯接此表中的兩個記錄并傳遞引用這兩個表的選擇條件。例如，以下將編譯（在LinqPad中），void GetData2(Expression<Func<Tuple<CustomerTransaction,CustomerTransaction>, bool>> selection){ var baseQuery = (from ct1 in CustomerTransaction join ct2 in CustomerTransaction on ct1.MasterTransactionID equals ct2.RelatedTransactionID select new Tuple<CustomerTransaction, CustomerTransaction> ( ct1, ct2)) ; var query = baseQuery.Where(selection).Dump();}Expression<Func<Tuple<CustomerTransaction,CustomerTransaction>, bool>> query2 = r => r.Item1.CustomerID != r.Item2.CustomerID;GetData2(query2);但是，它不會運行，因為SQL無法處理元組。如果我嘗試以SQL可以理解的方式編寫此代碼，那么我將無法通過選擇標準，因為我不知道選擇的類型例如void GetData3( ??? selection){ var baseQuery = (from ct1 in CustomerTransaction join ct2 in CustomerTransaction on ct1.MasterTransactionID equals ct2.RelatedTransactionID select new { Customer1 = ct1.CustomerID, Customer2 = ct2.CustomerID } ); baseQuery.Where(selection).Dump();}顯然，實際查詢更為復雜，并且它們是多個選擇條件，因此，我試圖避免為每個可能的部分條件重復查詢。有沒有辦法解決？
1 回答
炎炎設計
TA貢獻1808條經驗 獲得超4個贊
您可以創(chuàng)建一個表示您的join結果的顯式類，并Where在該類上創(chuàng)建表達式：
public class CT2 {
public CustomerTransaction ct1;
public CustomerTransaction ct2;
}
然后，您可以在查詢和Where表達式中使用該類：
void GetData2(Expression<Func<CT2, bool>> selection) {
var baseQuery = from ct1 in db.CustomerTransaction
join ct2 in db.CustomerTransaction on ct1.MasterTransactionID equals ct2.RelatedTransactionID
select new CT2 { ct1 = ct1, ct2 = ct2 };
var query = baseQuery.Where(selection).Dump();
}
Expression<Func<CT2, bool>> query2 =
r => r.ct1.CustomerID != r.ct2.CustomerID;
GetData2(query2);
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