用Dictionary替换switch case

用switch case处理一个很长的判断，例如56个民族01代表汉族，02代表藏族，03代表壮族...，当传入数字想获取民族名称时就得写56个case，当传入民族获取背后的数字时，又得再写56个case，如下所示：

private string GetNationValue(string s)
{
    string result = "5";
    switch (s)
    {
        case "01":
            result = "汉族";
            break;
        case "02":
            result = "藏族";
            break;
        case "03":
            result = "壮族";
            break;
        case "04":
            result = "朝鲜族";
            break;
        //这里省略其它......
    }
    return result;
}
private string GetNationKey(string s)
{
    string result = "5";
    switch (s)
    {
        case "汉族":
            result = "01";
            break;
        case "藏族":
            result = "02";
            break;
        case "壮族":
            result = "03";
            break;
        case "朝鲜族":
            result = "04";
            break;
        //这里省略其它......
    }
    return result;
}

这么长的代码很丑陋，要修改也不容易，可以通过Dictionary来改进，键和值是成对写在一起的，非常容易维护，改写后代码如下：

public enum FormatType
{
    GetKey,
    GetValue
}
public class Format
{
    private static string Get(Dictionary<string, string> dict, FormatType formatType, string code)
    {
        if (formatType == FormatType.GetKey)
             return dict.FirstOrDefault(d => d.Value == code).Key;
        else
             return dict.FirstOrDefault(d => d.Key == code).Value;
    }
    public static string GetNation(FormatType formatType, string code)
    {
       Dictionary<string, string> dict = new Dictionary<string, string>{
                {"01","汉族"},
                {"02","藏族"},
                {"03","壮族"},
                {"04","朝鲜族"}
                //这里省略其它......
        };
       return Get(dict, formatType, code);
   }
}

使用：
获取"汉族"的编码

string key = Format.GetNation(FormatType.GetKey, "汉族");

获取"01"代表的民族

string value = Format.GetNation(FormatType.GetValue, "01");