两种初始化方式及其区别：

using System;
using System.Collections.Generic;
class Program
{
    public static void Main(string[] args)
    {
        //////////////////////////////////////////////////////
        //两种方式
        //方式1
         var dic1 = new Dictionary<string, string>()
        {
            {"key1", "aa"},
            { "key2" , "bb"}
        };
        //方式2
        var dic2 = new Dictionary<string, string>
        {
            ["key1"] = "aa",
            ["key2"] = "bb"
        };
        
        ////////////////////////////////////////////////////
        //两种方式的区别：
        //方式1
         var dic3 = new Dictionary<string, string>()
        {
            {"key1", "aa"},
            //{ "key1" , "bb"} //不能这么写
        };
        //方式2
        var dic4 = new Dictionary<string, string>
        {
            ["key1"] = "aa",
            ["key1"] = "bb" //可以这么写
        };
    }
}