C# 大小写转换

C#通过ToUpper()方法将字符串转换成大写，代码如下：

string sentence= "this is in upper case.";

Console.WriteLine(sentence.ToUpper());

C#通过ToLower()方法将字符串转换成小写，代码如下：

string sentence= "this is in Lower case.";

Console.WriteLine(sentence.ToLower());