public string Substring(int startIndex);//The substring starts at a specified character position and continues to the end of the string.
public string Substring(int startIndex, int length);//The substring starts at a specified character position and taking length no of character from the startIndex.
因此,对于这个场景,您可以使用下面这样的第一个方法:
var str = "hello world!";
str = str.Substring(10);