parameterCheck.cs  
   
public class parameterCheck{ 
    public static bool isEmail(string emailString){ 
        return System.Text.RegularExpressions.Regex.IsMatch(emailString, "['\\w_-]+(\\.
['\\w_-]+)*@['\\w_-]+(\\.['\\w_-]+)*\\.[a-zA-Z]{2,4}"); 
    } 
    public static bool isInt(string intString){ 
        return System.Text.RegularExpressions.Regex.IsMatch(intString ,"^(\\d{5}-\\d{4})|
(\\d{5})$"); 
    } 
    public static bool isUSZip(string zipString){ 
        return System.Text.RegularExpressions.Regex.IsMatch(zipString ,"^-[0-9]+$|^[0-9]
+$"); 
    } 
}

<appSettings> 
    <add key="safeParameters" value="OrderID-int32,CustomerEmail-email,ShippingZipcode-
USzip" /> 
</appSettings>

protected void Application_BeginRequest(Object sender, EventArgs e){ 
    String[] safeParameters = System.Configuration.ConfigurationSettings.AppSettings
["safeParameters"].ToString().Split(','); 
    for(int i= 0 ;i < safeParameters.Length; i++){ 
        String parameterName = safeParameters[i].Split('-')[0]; 
        String parameterType = safeParameters[i].Split('-')[1]; 
        isValidParameter(parameterName, parameterType); 
    } 
}  

public void isValidParameter(string parameterName, string parameterType){ 
    string parameterValue = Request.QueryString[parameterName]; 
    if(parameterValue == null) return; 

    if(parameterType.Equals("int32")){ 
        if(!parameterCheck.isInt(parameterValue)) Response.Redirect("parameterError.aspx"); 
    } 
    else if (parameterType.Equals("double")){ 
        if(!parameterCheck.isDouble(parameterValue)) Response.Redirect("parameterError.aspx"); 
    } 
    else if (parameterType.Equals("USzip")){ 
        if(!parameterCheck.isUSZip(parameterValue)) Response.Redirect("parameterError.aspx"); 
    } 
    else if (parameterType.Equals("email")){ 
        if(!parameterCheck.isEmail(parameterValue)) Response.Redirect("parameterError.aspx"); 
    } 
}