使用LINQ to從比較兩個列表，其中

Question

我有默認值定義我StateRegions屬性的默認值的屬性之一返回一個列表，例如：

public string Vermont 
     { 
      get 
      { 
       return string.IsNullOrEmpty(_region) ? "NorthEast" : _region; 
      } 

      set { _region = value; } 
     } 

     public string NewHampshire 
     { 
      get 
      { 
       return string.IsNullOrEmpty(_region) ? "NorthEast" : _region; 
      } 

      set { _region = value; } 
     } 

     public string Massachusetts 
     { 
      get 
      { 
       return string.IsNullOrEmpty(_region) ? "NorthEast" : _region; 
      } 

      set { _region = value; } 
     } 

     public string RhodeIsland 
     { 
      get 
      { 
       return string.IsNullOrEmpty(_region) ? "NorthEast" : _region; 
      } 

      set { _region = value; } 
     } 

     public string NewYork 
     { 
      get 
      { 
       return string.IsNullOrEmpty(_region) ? "NorthEast" : _region; 
      } 

      set { _region = value; } 
     } 

     public string Pennsylvania 
     { 
      get 
      { 
       return string.IsNullOrEmpty(_region) ? "NorthEast" : _region; 
      } 

      set { _region = value; } 
     } 

現在我想建立一個基於該區域的列表在DB中聲明。這是基本的代碼/僞代碼：

 // 1) What states have customers? 
     List<string> states = GetStatesHavingCustomers(); 

     // 2) What are the regions that correspond to US States? 
     List<StateRegions> regions = new List<StateRegions>(); 


     // Lets get the get the states in the DB and 
     // put the corresponding regions in a list 

任何想法如何在LINQ中做到這一點？

Answer 1

我不太瞭解stateRegion字符串屬性或它們的用途。如果你可以將它們替換成字典，那麼在實現這個時就會遇到一些麻煩。

// assuming this returns a List<string> containing state names such as "Vermont" 
var states = GetStatesHavingCustomers(); 

var stateRegions = new Dictionary<string, string>(); 
stateRegions["Vermont"] = "NorthEast"; 
stateRegions["Massacheusetts"] = "NorthEast"; 
//etc.. 

// Returns an IEnumerable<string>, with distinct entries 
var dbRegions = (from entry in stateRegions where states.Contains(entry.Key) select entry.Value).Distinct();