string test = "<IMG src="http://www.baidu.com/upload/2009_11/09112110144808.jpg" border=0><IMG src="upload/2009_11/09112110144808.jpg" border=0><img alt="" src="/upload/201510/28/201510281002087002.png">"; string outhost = "www.myname.com"; Regex reg = new Regex(@"(?is)(?<=<imgs+alt=.*src=(['""]?))(?!http://)(?=[^'""s>]+1)"); string result = reg.Replace(test, "http://" + outhost + "/");
string test = "<IMG src="http://www.baidu.com/upload/2009_11/09112110144808.jpg" border=0><IMG src="upload/2009_11/09112110144808.jpg" border=0>"; string outhost = "www.myname.com"; Regex reg = new Regex(@"(?is)(?<=<imgs+src=(['""]?))(?!http://)(?=[^'""s>]+1)"); string result = reg.Replace(test, "http://" + outhost + "/");