如果LINQ中有其他条件

Question

我正在学习LINQ to sql的过程。

是否有可能在LINQ to SQL中写入以下条件？

条件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; } 
    } 

麻烦引导。

更新编辑：

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" 
    } 

这将是一个办法？

Answer 1

因为这是所有代码端，你可以用你运行你的LINQ查询后，使用普通的if-else模式。

实施例：

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"; 
}  

由于LINQ只是被用来确定记录是否存在，不过，我建议使用的.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

它看起来像你总是在相同的条件下查询，而你有条件地做出的唯一反应就是返回结果的数量。你可以用where条件得到结果，然后在结果计数周围放一个if语句。

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...