EF每箱

Question

擴展查詢我有以下情況：

我需要在一個EF上下文中執行以下LINQ查詢

from table1 in context.TableOne 
join table2 in context.TableTwo on table1.SomeFKId equals table2.Id 
join table3 in context.TableThree on table2.SomeFKId equals table3.Id 
... 
join tableN in context.TableN on tableN_1.SomeFKId equals tableN.Id 
where case1 && case2 && case3 ... && caseN 
select new TablesDto { VarOne = table1.Var , VarTwo = tableN_2.var } 

我的問題是，我想使用向度的同一查詢senarios有很多延伸。 我寧願不多次寫（DRY原則），只是擴大它，但不以犧牲效率和速度爲代價。

這就是說，如果我想將第一個表與另一個表連接起來，我可以擴展Dto以合併其餘的變量，但是如果我要遍歷行，則需要每行的查詢來擴展它。由於我在談論100到5000行，即使迭代也需要一些時間。

擴展包括：其他情況（case1，case2等）和其他連接。

Extention例子：

from table1 in context.TableOne 
join table2 in context.TableTwo on table1.SomeFKId equals table2.Id 
join table3 in context.TableThree on table2.SomeFKId equals table3.Id 
... 
join tableN in context.TableN on tableN_1.SomeFKId equals tableN.Id 
join extTable in context.TableExt on table2.SomeFKId equals extTable.Id 
where case1 && case2 && case3 ... && caseN || extTable.NumOfSmth == 4 
select new ExtTablesDto { VarOne = table1.Var , VarTwo = tableN_2.var , ExtVar = extTable.Name } 

Answer 1

嘗試......

void Main() 
{ 
    using(var dal = new DataAccessLayer()) 
    { 
     var items = dal.TablesDtoQuery.Case1().Case2().ToList(); 
    } 
} 

public class DataAccessLayer : IDisposable 
{ 
    private DbContext context; 

    public void Dispose() 
    { 
     context.Dispose(); 
    } 

    public IQueryable<TablesDto> TablesDtoQuery 
    { 
     get 
     { 
      return 
       from table1 in context.TableOne 
       join table2 in context.TableTwo on table1.SomeFKId equals table2.Id 
       join table3 in context.TableThree on table2.SomeFKId equals table3.Id 
       ... 
       join tableN in context.TableN on tableN_1.SomeFKId equals tableN.Id 
       where case1 && case2 && case3 ... && caseN 
       select new TablesDto { VarOne = table1.Var , VarTwo = tableN_2.var }; 
     } 
    } 
} 

public static class TablesDtoQueryExtension 
{ 
    public IQueryable<TablesDto> Case1(this IQueryable<TablesDto> query) 
    { 
     return from t in query 
      where ... 
      select t; 
    } 

    public IQueryable<TablesDto> Case2(this IQueryable<TablesDto> query) 
    { 
     return from t in query 
      where ... 
      select t; 
    } 
} 

Answer 2

可以延長在那裏查詢很容易這樣

var query = from user in dbContext.Users where user.id = 10; 

if (x == 3) 
{ 
    query = query.where(p=>p.name == "test"); 
} 

等等，你可以在這裏擴展基本的查詢用戶ID = 10和名稱後，你將搜索=「測試」

如果你有一個EF模型，那麼你應該嘗試創建表之間存在的依賴關係，那麼你就需要加入他們在您的查詢