C# Dictionary用法总结

C# Dictionary用法总结

1、用法1：　常规用

　　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 pList = new  Dictionary();
    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、用法2：Dictionary的Value为一个数组

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

　　3、用法3： Dictionary的Value为一个类

//Dictionary的Value为一个类
public  static  void  DicSample3()
 {
     Dictionary stuList = new  Dictionary();
     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 备注：Dictionary的扩展方法使用

 

///
/// Dictionary的扩展方法使用
///
 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
{
    ///
    /// 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
    ///
    public  static  Dictionary TryAdd( this  Dictionary dict, TKey key, TValue value)
    {
        if  (dict.ContainsKey(key) == false )
            dict.Add(key, value);
        return  dict;
    }

    ///
    /// 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
    ///
    public  static  Dictionary AddOrPeplace( this  Dictionary dict, TKey key, TValue value)
    {
        dict[key] = value;
        return  dict;
    }

    ///
    /// 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
    ///
    public  static  TValue GetValue( this  Dictionary dict, TKey key, TValue defaultValue)
    {
        return  dict.ContainsKey(key)?dict[key] : defaultValue;
    }

    ///
    /// 向字典中批量添加键值对
    ///
    /// 如果已存在，是否替换
    public  static  Dictionary AddRange( this  Dictionary dict, IEnumerable> values, bool  replaceExisted)
    {
        foreach  ( var  item in  values)
        {
            if  (dict.ContainsKey(item.Key) == false  || replaceExisted)
                dict[item.Key] = item.Value;
        }
        return  dict;
    }


}

参考资料