三个查询组合成一个外部联接可能

Question

目前我有三个查询是这样的：

var query1 = (from a in dbContext.Table1 
       where a.email == someEmail 
       select a.Table1K).ToList(); 
var query2 = (from a in dbContext.Table2 
       where a.emailAddrerss == someEmail 
       select a.Table2K).ToList(); 
var query3 = (from a in dbContext.Table3 
       where a.email == someEmail 
       select a.Table3K).ToList(); 

if (query2.Any() || query3.Any()) 
{ 
    return false; 
} 

if(query1.Count == 1) 
{ 
    var x = query1[0]; 
    // do some stuff with that x value ... 
} 

是否有例如与外部的方式连接（我不是非常好，外连接），我们可以实现这在一个查询而不是三个查询？

Answer 1

我不认为实际的加入是合适的，但你确实有改善的机会很少：

• 不要叫上查询2或3 ToList如果你只是想检查任何结果：

• 如果只想从查询1 一个结果，称SingleOrDefault代替

  var query1 = (from a in dbContext.Table1 
         where a.email == someEmail 
         select a.Table1K); 
  var query2 = (from a in dbContext.Table2 
         where a.emailAddrerss == someEmail 
         select a.Table2K); 
  var query3 = (from a in dbContext.Table3 
         where a.email == someEmail 
         select a.Table3K); 
  
  
  if (query2.Any() || query3.Any()) 
  { 
      return false; 
  } 
  
  var x = query1.SingleOrDefault(); 
  if(x != null) 
  { 
      // do some stuff with that x value ... 
  }