C# Dictionary用法总结

work hard work smart 原文 C# Dictionary用法总结

1、常规用法

增加键值对之前需要判断是否存在该键，如果已经存在该键而且不判断，将抛出异常。所以这样每次都要进行判断，很麻烦，在备注里使用了一个扩展方法

public static void DicSample1()
{
 
    Dictionary<String, String> pList = new Dictionary<String, String>();
    try
    {
        if (pList.ContainsKey("Item1") == false)
        {
            pList.Add("Item1", "ZheJiang");
        }
        if (pList.ContainsKey("Item2")== false)
        {
            pList.Add("Item2", "ShangHai");
        }
        else
        {
            pList["Item2"] = "ShangHai";
        }
        if (pList.ContainsKey("Item3") == false)
        {
            pList.Add("Item3", "BeiJiang");
        }
         
    }
    catch (System.Exception e)
    {
        Console.WriteLine("Error: {0}", e.Message);
    }
   
 
    //判断是否存在相应的key并显示
    if (pList.ContainsKey("Item1"))
    {
        Console.WriteLine("Output: " + pList["Item1"]);
    }
 
    //遍历Key
    foreach (var key in pList.Keys)
    {
        Console.WriteLine("Output Key: {0}", key);
    }
 
    //遍历Value
    foreach (String value in pList.Values)
    {
        Console.WriteLine("Output Value: {0}", value);
    }
    //遍历Key和Value
    foreach (var dic in pList)
    {
        Console.WriteLine("Output Key : {0}, Value : {1} ", dic.Key, dic.Value);
    }
}

2、Dictionary的Value为一个数组

/// <summary>
/// Dictionary的Value为一个数组
/// </summary>
 public static void DicSample2()
 {
     Dictionary<String, String[]> dic = new Dictionary<String, String[]>();
     String[] ZheJiang =  { "Huzhou", "HangZhou", "TaiZhou" };
     String[] ShangHai = { "Budong", "Buxi" };
     dic.Add("ZJ", ZheJiang);
     dic.Add("SH", ShangHai);
     Console.WriteLine("Output :" + dic["ZJ"][0]);
 }

3、Dictionary的Value为一个类

//Dictionary的Value为一个类
public static void DicSample3()
 {
     Dictionary<String, Student> stuList = new Dictionary<String, Student>();
     Student stu = null;
     for (int i = 0; i < 3; i++ )
     {
         stu = new Student();
         stu.Name = i.ToString();
         stu.Name = "StuName" + i.ToString();
         stuList.Add(i.ToString(), stu);
     }
 
     foreach (var student in stuList)
     {
         Console.WriteLine("Output : Key {0}, Num : {1}, Name {2}", student.Key, student.Value.Name, student.Value.Name);
     }
 }

Student类：

public class Student
{
    public String Num { get; set; }
    public String Name { get; set; }
}

 4  扩展方法

/// <summary>
/// Dictionary的扩展方法使用
/// </summary>
 public static void DicSample4()
 {
     //1)普通调用
     Dictionary<int, String> dict = new Dictionary<int, String>();
     DictionaryExtensionMethodClass.TryAdd(dict, 1, "ZhangSan");
     DictionaryExtensionMethodClass.TryAdd(dict, 2, "WangWu");
     DictionaryExtensionMethodClass.AddOrPeplace(dict, 3, "WangWu");
     DictionaryExtensionMethodClass.AddOrPeplace(dict, 3, "ZhangWu");
     DictionaryExtensionMethodClass.TryAdd(dict, 2, "LiSi");
 
     //2)TryAdd 和 AddOrReplace 这两个方法具有较强自我描述能力，用起来很省心，而且也简单：
     dict.AddOrPeplace(20, "Orange");
     dict.TryAdd(21, "Banana");
     dict.TryAdd(22, "apple");
 
     //3)像Linq或jQuery一样连起来写  
     dict.TryAdd(10, "Bob")
         .TryAdd(11, "Tom")
         .AddOrPeplace(12, "Jom");
 
     //4) 获取值
     String F = "Ba";
     dict.TryGetValue(31, out F);
     Console.WriteLine("F : {0}",F);
 
     foreach (var dic in dict)
     {
         Console.WriteLine("Output : Key : {0}, Value : {1}", dic.Key, dic.Value);
     }
     //5)下面是使用GetValue获取值
     var v1 = dict.GetValue(111,null);
     var v2 = dict.GetValue(10,"abc");
 
     //6)批量添加
     var dict1 = new Dictionary<int,int>();
     dict1.AddOrPeplace(3, 3);
     dict1.AddOrPeplace(5, 5);
 
     var dict2 = new Dictionary<int, int>();
     dict2.AddOrPeplace(1, 1);
     dict2.AddOrPeplace(4, 4);
     dict2.AddRange(dict1, false);
 }

扩展方法所在的类

public static class DictionaryExtensionMethodClass
{
    /// <summary>
    /// 尝试将键和值添加到字典中：如果不存在，才添加；存在，不添加也不抛导常
    /// </summary>
    public static Dictionary<TKey, TValue> TryAdd<TKey, TValue>(this Dictionary<TKey, TValue> dict, TKey key, TValue value)
    {
        if (dict.ContainsKey(key) == false)
            dict.Add(key, value);
        return dict;
    }
 
    /// <summary>
    /// 将键和值添加或替换到字典中：如果不存在，则添加；存在，则替换
    /// </summary>
    public static Dictionary<TKey, TValue> AddOrPeplace<TKey, TValue>(this Dictionary<TKey, TValue> dict, TKey key, TValue value)
    {
        dict[key] = value;
        return dict;
    }
 
    /// <summary>
    /// 获取与指定的键相关联的值，如果没有则返回输入的默认值
    /// </summary>
    public static TValue GetValue<TKey, TValue>(this Dictionary<TKey, TValue> dict, TKey key, TValue defaultValue)
    {
        return dict.ContainsKey(key)?dict[key] : defaultValue;
    }
 
    /// <summary>
    /// 向字典中批量添加键值对
    /// </summary>
    /// <param name="replaceExisted">如果已存在，是否替换</param>
    public static Dictionary<TKey, TValue> AddRange<TKey, TValue>(this Dictionary<TKey, TValue> dict, IEnumerable<KeyValuePair<TKey, TValue>> values, bool replaceExisted)
    {
        foreach (var item in values)
        {
            if (dict.ContainsKey(item.Key) == false || replaceExisted)
                dict[item.Key] = item.Value;
        }
        return dict;
    }
 
 
}