在C#中获取子字符串？

string str = "Hello World!";
string subStr = str.Substring(0, 5);
Console.WriteLine(subStr); // 输出 "Hello"

string str = "Hello World!";
int index = str.IndexOf("o");
Console.WriteLine(index); // 输出 7

string str = "Hello|World|!";
string[] substrings = str.Split('|');
foreach (string subStr in substrings)
{
    Console.WriteLine(subStr);
}