using System;
using System.Text.RegularExpressions;
public class Test
{
public static void Main()
{
var result = Regex.Replace(_input, @"<(?<close>/?)((?!img|br).)*?>", @"<${close}p>");
Console.WriteLine(result);
}
private static string _input =
@"
<em></ em >
<font style=""text-align:justify;"">aaaaaaaaaaa</font>
<img src=""abc.jpg""/>
<iframe src=""somelink.com"">
</iframe>
<br>
<br/>
";
}
dXNpbmcgU3lzdGVtOwp1c2luZyBTeXN0ZW0uVGV4dC5SZWd1bGFyRXhwcmVzc2lvbnM7CgpwdWJsaWMgY2xhc3MgVGVzdAp7CglwdWJsaWMgc3RhdGljIHZvaWQgTWFpbigpCgl7CgkJdmFyIHJlc3VsdCA9IFJlZ2V4LlJlcGxhY2UoX2lucHV0LCBAIjwoPzxjbG9zZT4vPykoKD8haW1nfGJyKS4pKj8+IiwgQCI8JHtjbG9zZX1wPiIpOwoJCUNvbnNvbGUuV3JpdGVMaW5lKHJlc3VsdCk7Cgl9CgkKCXByaXZhdGUgc3RhdGljIHN0cmluZyBfaW5wdXQgPQpAIgo8ZW0+PC8gZW0gPiAKPGZvbnQgc3R5bGU9IiJ0ZXh0LWFsaWduOmp1c3RpZnk7IiI+YWFhYWFhYWFhYWE8L2ZvbnQ+CjxpbWcgc3JjPSIiYWJjLmpwZyIiLz4KPGlmcmFtZSBzcmM9IiJzb21lbGluay5jb20iIj4gCjwvaWZyYW1lPgo8YnI+Cjxici8+CiI7Cn0=