int start = input.IndexOf("(") + 1;
int length = input.IndexOf(")") - start;
output = input.Substring(start, length);

我认为regex方法更好，但如果你想使用卑微的子字符串

string input= "my name is (Jayne C)";
int start = input.IndexOf("(");
int stop = input.IndexOf(")");
string output = input.Substring(start+1, stop - start - 1);

or

string input = "my name is (Jayne C)";
string output  = input.Substring(input.IndexOf("(") +1, input.IndexOf(")")- input.IndexOf("(")- 1);

string input = "User name (sales)";

string output = input.Substring(input.IndexOf('(') + 1, input.IndexOf(')') - input.IndexOf('(') - 1);

 var input = "12(34)1(12)(14)234";
 var output = "";
 for (int i = 0; i < input.Length; i++)
 {
     if (input[i] == '(')
     {
         var start = i + 1;
         var end = input.IndexOf(')', i + 1);
         output += input.Substring(start, end - start) + ",";
     }
 }

 if (output.Length > 0) // remove last comma
  output = output.Remove(output.Length - 1);

输出:“34,12,14”

我最近一直在使用和滥用c# 9，甚至在一些可疑的场景中，我也忍不住要加入span…只是为了好玩，以下是上述答案的变体:

var input = "User name (sales)";
var txtSpan = input.AsSpan();
var startPoint = txtSpan.IndexOf('(') + 1;
var length = txtSpan.LastIndexOf(')') - startPoint;
var output = txtSpan.Slice(startPoint, length);

对于OP的特定场景，它产生正确的输出。 (就我个人而言，我会使用其他人发布的RegEx。在上述解决方案崩溃的情况下，更容易解决更棘手的情况)。

我为自己的项目做了一个更好的版本(作为扩展方法):

//Note: This only captures the first occurrence, but 
//can be easily modified to scan across the text (I'd prefer Slicing a Span)  
public static string ExtractFromBetweenChars(this string txt, char openChar, char closeChar)
{
    ReadOnlySpan<char> span = txt.AsSpan();
    int firstCharPos = span.IndexOf(openChar);
    int lastCharPos = -1;

    if (firstCharPos != -1) 
    { 
        for (int n = firstCharPos + 1; n < span.Length; n++)
        {
            if (span[n] == openChar) firstCharPos = n; //This allows the opening char position to change
            if (span[n] == closeChar) lastCharPos = n;
            if (lastCharPos > firstCharPos) break;
            //This would correctly extract "sales" from this [contrived]
            //example: "just (a (name (sales) )))(test"
        }
        return span.Slice(firstCharPos + 1, lastCharPos - firstCharPos - 1).ToString();
    }
    return "";
}

一个非常简单的方法是使用正则表达式:

Regex.Match("User name (sales)", @"\(([^)]*)\)").Groups[1].Value

作为对(非常有趣的)评论的回应，这里是同一个正则表达式的一些解释:

\(             # Escaped parenthesis, means "starts with a '(' character"
    (          # Parentheses in a regex mean "put (capture) the stuff 
               #     in between into the Groups array" 
       [^)]    # Any character that is not a ')' character
       *       # Zero or more occurrences of the aforementioned "non ')' char"
    )          # Close the capturing group
\)             # "Ends with a ')' character"