How to limit the number of requests per user to a page

Question

this is my html code

<asp:TextBox ID="Txtcomments" runat="server" TextMode="MultiLine"></asp:TextBox>
<br />
<asp:Button ID="BtnPost" runat="server" Text="Post" OnClick="BtnPost_Click" />
<br />
<asp:Label ID="Label1" runat="server" Text=""></asp:Label>
<br />

my problem i haave a sample webform like this if a user makes a comment it will save in the database but i had to restrict a particular user like that he should make only 2 comments(requests) within 5 minutes of time if the same user wants to make 3rd comment he should be displaying a message that request limit exceeded

 

first i thought restricting user based on ip but using the below code it blocks all the users of the particular host but not a single user

public partial class webThrottle : System.Web.UI.Page
{
public static string date;
public static string strSessionID="first";
protected void Page_Load(object sender, EventArgs e)
{
}
protected void BtnPost_Click(object sender, EventArgs e)
{
string ipaddress;
ipaddress = Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
if (ipaddress == "" || ipaddress == null)
ipaddress = Request.ServerVariables["REMOTE_ADDR"];
string SessionID = Session.SessionID;
var Throttle = new Throttler();
if (Throttle.RequestShouldBeThrottled(ipaddress))
{
Label1.Text = "Access Denied because of Too Many requests";
TimeSpan span = (Convert.ToDateTime(Throttler.NextAccessDate) - Convert.ToDateTime(DateTime.Now));
string diff= String.Format("{0} minutes, {1} seconds", span.Minutes, span.Seconds);
Label4.Text = "Elapsed Time = "+" "+"Try Again After "+diff;
}
else
{
SqlConnection con = new SqlConnection("Server=DELL-PC; User Id=sa;Password=123;Database=comments");
con.Open();
SqlCommand cmd = new SqlCommand("insert into tbl_comments(comment, ipAddress, Date)values(@p1, @p2, @p4)", con);
cmd.Parameters.AddWithValue("@p1", Txtcomments.Text);
cmd.Parameters.AddWithValue("@p2", ipaddress);
date = DateTime.Now.ToString();
cmd.Parameters.AddWithValue("@p4", date);
int i = cmd.ExecuteNonQuery();
if (i > 0)
{
Label1.Text = "Your comment has been posted successfully";
//Label2.Text = " " ;
//Label3.Text = " ";
Label4.Text = " " ;
}
con.Close();
}
}
}
public class Throttler
{
private int _requestLimit;
private int _timeoutInSeconds;
private string _key;
public static string NextAccessDate;
public bool RequestShouldBeThrottled(string key, int requestLimit = 5, int timeoutInSeconds = 180)
{
_requestLimit = requestLimit;
_timeoutInSeconds = timeoutInSeconds;
_key = key;
ThrottleInfo throttleInfo = (ThrottleInfo)HttpRuntime.Cache[_key];
if (throttleInfo == null)
{
throttleInfo = new ThrottleInfo
{
ExpiresAt = DateTime.Now.AddSeconds(_timeoutInSeconds),
RequestCount = 0,
};
NextAccessDate=throttleInfo.ExpiresAt.ToString();
}
throttleInfo.RequestCount++;
HttpRuntime.Cache.Add(_key,
throttleInfo,
null,
throttleInfo.ExpiresAt,
Cache.NoSlidingExpiration,
CacheItemPriority.Normal,
null);
return (throttleInfo.RequestCount > _requestLimit);
}
}
public class ThrottleInfo
{
public DateTime ExpiresAt { get; set; }
public int RequestCount { get; set; }
}