如果LINQ中有其他條件

Question

我正在學習LINQ to sql的過程。

是否有可能在LINQ to SQL中寫入以下條件？

條件1

var query1 = 
      if 
      from q in db.Students 
      q.fees =="paid" && q.activites == "good" && count == 0 
      select q 

       save "OK" to the property result. 

      else 
      from q in db.Students 
      q.fees =="paid" && q.activites == "good" && count == 2 
      select q 
      save "better" to the property result. 

      else 
      from q in db.Students 
      q.fees =="paid" && q.activites == "good" && count > 2 
      select q 
      save "bad" to the property result. 


    private string _result; 
    public string Result 
    { 
     get { return this._result; ; } 
     set { this._result; = value; } 
    } 

麻煩引導。

更新編輯：

var query1 =     
      (from q in db.Students 
      q.fees =="paid" && q.activites == "good" 
      select q).Any(); 

    if(count ==0 && query1 == true) 
    { 
    this.Result = "OK" 
    } 
    esle if(count == 2 && query1 == true) 
    { 
    this.Result = "better" 
    } 
    esle 
    { 
    this.Result = "bad" 
    } 

這將是一個辦法？

Answer 1

因爲這是所有代碼端，你可以用你運行你的LINQ查詢後，使用普通的if-else模式。

實施例：

var query1 =     
     from q in db.Students 
     q.fees =="paid" && q.activites == "good" 
     select q; 

if(count ==0 && query1.Count() > 0) 
{ 
    this.Result = "OK"; 
} 
else if(count == 2 && query1.Count() > 0) 
{ 
    this.Result = "better"; 
} 
else 
{ 
    this.Result = "bad"; 
}  

由於LINQ只是被用來確定記錄是否存在，不過，我建議使用的.Any()方法。

var recordsFound = db.Students.Any(q => q.fees =="paid" && q.activites == "good"); 

if(count == 0 && recordsFound) 
{ 
    this.Result = "OK"; 
} 
else if(count == 2 && recordsFound) 
{ 
    this.Result = "better"; 
} 
else 
{ 
    this.Result = "bad"; 
} 

Answer 2

它看起來像你總是在相同的條件下查詢，而你有條件地做出的唯一反應就是返回結果的數量。你可以用where條件得到結果，然後在結果計數週圍放一個if語句。

var count = (from q in db.Students 
where q.fees == "paid" && q.activities == "good" 
select q).Count(); 

if(count == 0){ 
    //do something 
} 
else if(count == 2){ 
    //do something 
} 
///etc...