LINQ to SQL多次查詢同一列

Question

我有一堆參數傳入使用LINQ to SQL的C＃方法。所有這些參數都是來自UI的過濾器。我需要篩選的四個參數位於同一個表的同一列中。例如，該表可能看起來像：

ID | FK_ID | Name | Value 

1 1 Param1 p1Val 
2 1 Param2 p2Val 
3 1 Param3 p3.Val 
3 1 Param4 p4.Val 

我需要的濾波器參數和匹配到值列，並確保該名稱是正確的。目前，我通過多次加入同一張表來做到這一點......但我擔心這太低效了。什麼是最好的方法來做到這一點？我想我想動態構建查詢，這樣我就可以檢查設置了哪些過濾器，但是我正在努力應該如何構建我的結果集。 現在，它看起來像：（FYI ContextProperties是有問題的表）

var result = 

from f in dataContext.Faults 
join m in dataContext.Messages on f.FaultID equals m.FaultID    
join c in dataContext.ContextProperties on m.MessageID equals c.MessageID 
join cp in dataContext.ContextProperties on c.MessageID equals cp.MessageID 
join cpp in dataContext.ContextProperties on cp.MessageID equals cpp.MessageID 
join cppp in dataContext.ContextProperties on cpp.MessageID equals cppp.MessageID 
where (f.DateTime >= initDate && f.DateTime <= finishDate) && 
        f.FaultID == (faultID != Guid.Empty ? faultID : f.FaultID) && 
        f.Application == (!string.IsNullOrEmpty(application) ? application : f.Application) && 
        f.FaultCode == (!string.IsNullOrEmpty(faultCode) ? faultCode : f.FaultCode) && 
        f.FailureCategory == (!string.IsNullOrEmpty(failureCategory) ? failureCategory : f.FailureCategory) && 
        f.ErrorType == (!string.IsNullOrEmpty(errorType) ? errorType : f.ErrorType) && 
        (f.FaultSeverity >= 0 && f.FaultSeverity <= maxFaultSeverity) 
        where (c.Value.ToString() == (!string.IsNullOrEmpty(geniusReference) ? geniusReference : c.Value.ToString()) 
         && c.Name.ToString() == "GeniusReference") 
        where (cp.Value.ToString() == (!string.IsNullOrEmpty(programNumber) ? programNumber : cp.Value.ToString()) 
         && cp.Name.ToString() == "ProgramGeniusNumber") 
        where (cpp.Value.ToString() == (!string.IsNullOrEmpty(platform) ? platform : cpp.Value.ToString()) 
         && cpp.Name.ToString() == "Platform") 
        where (cppp.Value.ToString() == (!string.IsNullOrEmpty(modifiedBy) ? modifiedBy : cppp.Value.ToString()) 
         && cppp.Name.ToString() == "ModifiedBy") 
        select new FaultsWithFilters { 
                DateTime = f.DateTime 
                ,FaultID = f.FaultID 
                ,Scope = f.Scope 
                ,FaultCode = f.FaultCode 
                ,FaultSeverity = f.FaultSeverity 
                ,ErrorType = f.ErrorType 
                ,Description = f.Description 
                ,FaultDescription = f.FaultDescription 
                ,FailureCategory = f.FailureCategory 
                ,GeniusReference = c.Value.ToString() 
                ,ProgramNumber = cp.Value.ToString() 
                ,Platform = cpp.Value.ToString() 
                ,ModifiedBy = cppp.Value.ToString() 
                }; 

接着一堆，語句和選擇的。先謝謝您的幫助！ PS抱歉糟糕的格式。

Answer 1

在當時創建您的查詢一個子句，而不是真的壞看field == (filterSet ? filter : field)。

首先加入所有必要的表：

var query = dataContext.Faults.Join(dataContext.Messages, f => f.FaultID, m => mFaultID, new { f, m }) 
           .Join(dataContext.ContextProperties, x => x.m.MessageID, c => c.MessageID, new { x.f, x.m, c }); 
           // add all other joins here 
           // and all where conditions that are always valid 

然後添加條件where條件：

if(!string.IsNullOrEmpty(geniusReference)) 
{ 
    query = query.Where(x => x.c.Value.ToString() == geniusReference); 
} 

// instead of: 
// where (c.Value.ToString() == (!string.IsNullOrEmpty(geniusReference) ? geniusReference : c.Value.ToString()) 

在末尾添加投影：

var results = from x in query 
       select new FaultsWithFilters { 
        DateTime = x.f.DateTime 
        ,FaultID = x.f.FaultID 
        ,Scope = x.f.Scope 
        ,FaultCode = x.f.FaultCode 
        ,FaultSeverity = x.f.FaultSeverity 
        ,ErrorType = x.f.ErrorType 
        ,Description = x.f.Description 
        ,FaultDescription = x.f.FaultDescription 
        ,FailureCategory = x.f.FailureCategory 
        ,GeniusReference = x.c.Value.ToString() 
        ,ProgramNumber = x.cp.Value.ToString() 
        ,Platform = x.cpp.Value.ToString() 
        ,ModifiedBy = x.cppp.Value.ToString() 
       };