真有意思

string str = "<img onload='_commentImageResize(this,350);' title=\"魅力四射\" src=\"/i/face/1.gif\">AAAAA<img onload='_commentImageResize(this,350);' title=\"吻\" src=\"/i/face/33.gif\">BBBBB<img onload='_commentImageResize(this,350);' title=\"大笑\" src=\"/i/face/98.gif\">CCC<img onload='_commentImageResize(this,350);' title=\"微笑\" src=\"/i/face/90.gif\">";

string pattern = "<img.+?(\\d+)\\.gif\">(\\w*)";

System.Text.RegularExpressions.Regex reg = new System.Text.RegularExpressions.Regex(pattern, System.Text.RegularExpressions.RegexOptions.IgnoreCase);

string result = reg.Replace(str, "{$$" + "${1}" + "}" + "${2}\n");