Extracting a sub-string in C#

I am new to c# programming and I want to ask a question.

How can I get the value in () and store it in another string. example:

I have string

s1="here there (hi)";

How can I get

开发者_如何学C

s2="hi";

the () will always be at the end of the sentence (never at first or in between).

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string s1 = "abc (hi)";
string s2 = s1.Substring(s1.LastIndexOf("(") + 1, s1.LastIndexOf(")") - s1.LastIndexOf("(") - 1);

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string s2 = s1.Substring(s1.LastIndexOf("(") + 1, s1.LastIndexOf(")") - s1.LastIndexOf("(") - 1);

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 string e1 = "here there (hi)";
//Extraction 
 string s2 = e1.Substring(e1.IndexOf("(")+1, (e1.LastIndexOf(")") - e1.IndexOf("("))-1);