It is very simple. Still here you go
string html = "<table border = '1'><tr><td>Name</td><td>Email</td><td>Phone</td></tr><tr><td>{Name}</td><td>{Email}</td><td>{Phone}</td></tr></table>";
string name = "Mudassar Khan";
string email = "mak@123.com ";
string phone = "8899001821";
html = html.Replace("{Name}", name).Replace("{Phone}", phone).Replace("{Email}", email);