選擇從字典查找值，但來自ConcurrentDictionary不

Question

今天，我在做一些測試與ConcurrentDictionary和詞典選擇：

class MyTest 
{ 
    public int Row { get; private set; } 
    public int Col { get; private set; } 
    public string Value { get; private set; } 

    public MyTest(int row, int col, string value) 
    { 
     this.Col = col; 
     this.Row = row; 
     this.Value = value; 
    } 


    public override bool Equals(object obj) 
    { 
     MyTest other = obj as MyTest; 
     return base.Equals(other); 

    } 

    public override int GetHashCode() 
    { 
     return (Col.GetHashCode()^Row.GetHashCode()^Value.GetHashCode()); 
    } 

} 

使用實體上面，我創建並填補了ConcurrentDictionary和解釋，並試圖代碼如下：

ConcurrentDictionary<MyTest, List<MyTest>> _test = new ConcurrentDictionary<MyTest, List<MyTest>>(); 
    Dictionary<MyTest, List<MyTest>> _test2 = new Dictionary<MyTest, List<MyTest>>(); 

     MyTest dunno = _test.Values.AsParallel().Select(x => x.Find(a => a.Col == 1 && a.Row == 1)).FirstOrDefault(); 
     MyTest dunno2 = _test2.Values.AsParallel().Select(x => x.Find(a => a.Col == 1 && a.Row == 1)).FirstOrDefault(); 

第一個返回的值，但第二個不是，我做錯了什麼？

這是用於添加值的代碼：要調用AddOrUpdate

  _test.AddOrUpdate(cell10, 
      new List<MyTest> 
      { 
       new MyTest(1, 1, "ovpSOMEVALUEValue"), 
       new MyTest(1, 2, "ocpSOMEVALUEValue") 
      }, 
      (key, value) => value = new List<MyTest>()); 

     _test2.Add(cell10, 
      new List<MyTest> 
      { 
       new MyTest(1, 1, "ovpSOMEVALUEValue"), 
       new MyTest(1, 2, "ocpSOMEVALUEValue") 
      } 
      ); 

Answer 1

，和你的第三個參數是它應該創建一個新的空單，因此結果是你最終的空的清單。我猜測在這行代碼之前的某個地方，你正在使用相同的密鑰添加一個條目。

另請注意，Equals功能不正確。您正在比較參考值，而不是您在GetHashCode中使用的實際值。我建議您使用默認模板來覆蓋Equals：

 protected bool Equals(x other) { 
     return Row == other.Row && Col == other.Col && string.Equals(Value, other.Value); 
    } 

    public override bool Equals(object obj) 
    { 
     if (ReferenceEquals(null, obj)) return false; 
     if (ReferenceEquals(this, obj)) return true; 
     if (obj.GetType() != this.GetType()) return false; 
     return Equals((x) obj); 
    } 

    public override int GetHashCode() 
    { 
     unchecked 
     { 
      var hashCode = Row; 
      hashCode = (hashCode*397)^Col; 
      hashCode = (hashCode*397)^(Value != null ? Value.GetHashCode() : 0); 
      return hashCode; 
     } 
    }