how we remove the special character from any string 
for example
string sSpecailChar="rajesh have $280.00 Rs. only, What!?"
in this sample how remove the special character like $!.?
is the best solution of this problem

we use regex class which contain many important properties like relace(), split(), match() etc
we remove the special char from any string
for example:
firstly, we use System.Text.RegularExpressions namespce

string strData = "rajesh have $280.00 Rs. only, What!?";
        string pattern = "[^a-zA-Z0-9]+";
        Regex rgx = new Regex(pattern);
        Response.Write("<font color='green'>Before Replace: </font> " + strData+"<br/>");
        Response.Write("<font color='green'>After Repalce: </font>" + rgx.Replace(strData, " "));

output:
Before Replace: rajesh have $280.00 Rs. only, What!?
After Repalce: rajesh have 280 00 Rs only What