我有一个字典[mapData]
,如下所示,检查密钥是[Dictionary< string, DateTime >]
存在[mapData]
,但它不起作用:
var mapData = new Dictionary<Dictionary<string, DateTime>, List<Student>>();
foreach (var st in listStudent)
{
// Create Key
var dicKey = new Dictionary<string, DateTime>();
dicKey.Add(st.Name, st.Birthday);
// Get mapData
if (!mapData.ContainsKey(dicKey)) // ===> Can not check key exists
{
mapData.Add(dicKey, new List<Student>());
}
mapData[dicKey].Add(st);
}
我尝试使用扩展方法,如下所示,但也无法正常工作:
public static bool Contains<Tkey>(this Dictionary<Tkey, List<Student>> dic, Tkey key)
{
if (dic.ContainsKey(key))
return true;
return false;
}
任何有关这些的提示都会有很大帮助。提前谢谢。
答案 0 :(得分:2)
你不想去那里。复杂对象不是字典中的键。我建议将字典移动到值,并创建一个更像树的结构。
有一种方法可以让这个工作,但我会建议反对它出于上述原因:自定义IEqualityComparer
的实现,它将字典中的键与另一个字典进行比较。
答案 1 :(得分:2)
这是因为您尝试根据对象引用而不是关键内容查找密钥。
您的词典键是Key + value (string + DateTime)
引用的组合。
除非你重写并IEqualityComparer.
var objectA = new ObjectA();
var objectB = new ObjectA();
objectA != objectB
除非你重写等于。
<强> 修改 强>
此示例来自MSDN https://msdn.microsoft.com/en-us/library/ms132151(v=vs.110).aspx
using System;
using System.Collections.Generic;
class Example
{
static void Main()
{
BoxEqualityComparer boxEqC = new BoxEqualityComparer();
var boxes = new Dictionary<Box, string>(boxEqC);
var redBox = new Box(4, 3, 4);
AddBox(boxes, redBox, "red");
var blueBox = new Box(4, 3, 4);
AddBox(boxes, blueBox, "blue");
var greenBox = new Box(3, 4, 3);
AddBox(boxes, greenBox, "green");
Console.WriteLine();
Console.WriteLine("The dictionary contains {0} Box objects.",
boxes.Count);
}
private static void AddBox(Dictionary<Box, String> dict, Box box, String name)
{
try {
dict.Add(box, name);
}
catch (ArgumentException e) {
Console.WriteLine("Unable to add {0}: {1}", box, e.Message);
}
}
}
public class Box
{
public Box(int h, int l, int w)
{
this.Height = h;
this.Length = l;
this.Width = w;
}
public int Height { get; set; }
public int Length { get; set; }
public int Width { get; set; }
public override String ToString()
{
return String.Format("({0}, {1}, {2})", Height, Length, Width);
}
}
class BoxEqualityComparer : IEqualityComparer<Box>
{
public bool Equals(Box b1, Box b2)
{
if (b2 == null && b1 == null)
return true;
else if (b1 == null | b2 == null)
return false;
else if(b1.Height == b2.Height && b1.Length == b2.Length
&& b1.Width == b2.Width)
return true;
else
return false;
}
public int GetHashCode(Box bx)
{
int hCode = bx.Height ^ bx.Length ^ bx.Width;
return hCode.GetHashCode();
}
}
// The example displays the following output:
// Unable to add (4, 3, 4): An item with the same key has already been added.
//
// The dictionary contains 2 Box objects.