block user account after 3 invalid attempts ,it is web based site

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C#

ASP.NET

C#4.0

Hi folk's

I have a query regarding blocking a user account after 3 invalid user attempts it is web based application ,i want to block user account after 3 invalid account,

my code is in this way.....

static  DataTable dt = new DataTable();//getting the user name from db
    
   DataRow row ;
    Loginbal objbal = new Loginbal();
    public void  count_log()
    { 
        
        BAL_ClassLibrary.Rcm_service.LoginEntities get_login_details = login_values();
        int count = Convert.ToInt32(Session["logincount"]);//placing count value in session
        Session["loginuid"] = txt_username.Text.Trim();//placing username in session
        string username=get_login_details.username1;
        if (dt.Rows.Count > 0)
        {
            if (username == dt.Rows[0]["UserName"].ToString())
            {
                if (Convert.ToInt32(Session["logincount"]) >= 3)//chech if count is >= 3
                {
                    objbal.account_block(get_login_details);
                    ScriptManager.RegisterClientScriptBlock(Page, Page.GetType(), "Result", "alert('*Your Account is blocked')", true);
                    Session["logincount"] = 0;
                }
                else
                {
                    count += 1;//incrementing count invalid attempt
                    Session["logincount"] = count;
                    ScriptManager.RegisterClientScriptBlock(Page, Page.GetType(), "Result", "alert('*The username or password you entered is incorrect!')", true);
                }

            }
            else
            {                
                int rowcount = dt.Rows.Count;
             dt.Rows[0]["UserName"] = username;
             Session["logincount"] = 1;
             ScriptManager.RegisterClientScriptBlock(Page, Page.GetType(), "Result", "alert('*The username or password you entered is incorrect!')", true);
            }
        }
        else
        {
            dt.Columns.Add("UserName", typeof(System.String));
            row = dt.NewRow();
            int rowcount = dt.Rows.Count;
            row["UserName"]=username;
            dt.Rows.Add(row);
            Session["logincount"] = 1;
            ScriptManager.RegisterClientScriptBlock(Page, Page.GetType(), "Result", "alert('*The username or password you entered is incorrect!')", true);
        }                        
    }

i calling this fun when authentication is failed ...

It is working fine after three invalid attempt in database i have column just changing the flag active to inactive

Is fun() make any problem when huge number of users is accessing ...

because i am using static data-set to store the username and further to compare the username ...

please make doubt clear as soon as possible.....

plz help me out