public static string ClearStr(string yourStr)
{
string str = string.Empty;
str = Regex.Replace(yourStr,"<.+?>"," ", RegexOptions.IgnoreCase);//一个去掉所有HTML标记
str = Regex.Replace(yourStr, "/<(?!img).*?>/g", " ", RegexOptions.IgnoreCase);//这是保留Img和<br>
str = Regex.Replace(yourStr,"<(?!/?br|/?img)[^<>]*>","",RegexOptions.IgnoreCase);//保留Img和<Br>
return str;
}