替换span 文本

Question

<span id="span1">+</span>
用正则 替换为 
<span id="span1">-</span>
怎么写正则？

Answer 1

try...string test = "<span id=\"span1\">+</span>";
Regex reg = new Regex(@"(?is)(?<=<span\b[^>]*>)(?:(?!</?span\b).)*(?=</span>)");
string result = reg.Replace(test, "-");

Answer 2

sting s="";
string regexstr = @"(?<=<SPAN[^>]*>)[^<]*(?=</SPAN>)";
string s= Regex.Replace(str, regexstr, "-", RegexOptions.IgnoreCase);