c#函数后面的“【】”代表什么意思呢？

Question

大神你们好！我在看别人的代码风格是发现一个不熟悉的c#用法请大声指点一下！
public enum FileType
{
image = 1,
video = 2,
ppt = 3,
word = 4,
excel = 5,
pdf = 6,
other = 0,
}

---

public static Dictionary> getTypeDic()
{
Dictionary> fileExtensionDic = new Dictionary>()
{
{FileType.image ,
new List(){"jpg","jpeg","bmp","gif","png","tiff"}},
{FileType.video ,
new List(){"mp4","avi","wmv","rmvb","rm","mpeg","mpg","dat","flv","3pg","mov"}},
{FileType.word ,
new List(){"txt","text","doc","docx","docm","dot","dotx","dotm","rtf"}},
{FileType.ppt ,
new List(){"ppt","pptx","pptm","ppsx","potx","pot","ppam"}},
{FileType.excel ,
new List(){"xls","xlsm","xlts","xltx","xltm","xlsb","xlam"}},
{FileType.pdf ,
new List(){"pdf"}},
{FileType.other ,
new List(){"*"}}//TODO:这里可能会有问题，是否应该应用空字串来表达
};
return fileExtensionDic;
}
---------------------------------------------------------------------------

public static List getFileExtensions(FileType type)
{
return getTypeDic()[type]; //!!这里 函数名（）[] 很怪异？？？
}

Answer 1

这个叫做索引器，因为getTypeDic返回了一个字典类型，这里的type是字典里某个项的key，通过索引器得到对应的value
可以认为，索引器是数组下标的自然扩展。数组可以看成key是0 1 2 3 4...值是对应下标构成的字典。