ASP.NET

aspx.cs:-

string constr = ConfigurationManager.ConnectionStrings["CS"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {

        SqlCommand cmd = new SqlCommand("spRegisteruser", con);
        cmd.CommandType = CommandType.StoredProcedure;
        SqlParameter name = new SqlParameter("@name", txtusername.Text);
        SqlParameter mobile = new SqlParameter("@mobile", txtmobilenumber.Text);
        SqlParameter password = new SqlParameter("@password", txtpassword.Text);
        SqlParameter dropdown = new SqlParameter("@country",DropDownList1.SelectedItem.Value);
        cmd.Parameters.Add(name);
        cmd.Parameters.Add(dropdown);
        cmd.Parameters.Add(mobile);
        cmd.Parameters.Add(password);
        con.Open();
     int i=  cmd.ExecuteNonQuery();
        con.Close();
    }

    Sql table:-

Web.config:-

IE 11 giving XML5619: Incorrect document syntax

<customErrors mode="On">
  <error statusCode="404" redirect="~/Error/Page404" />
  <error statusCode="500" redirect="~/Error/Page500" />
</customErrors>

void Application_Error(object sender, EventArgs e)
        {
            if (HttpContext.Current.IsDebuggingEnabled)
            {
                // Pick up the Exception Error
                HttpException httpException = new HttpException();
                RouteData routeData = new RouteData();

                // Get our current controller and action
                string controller = Request.RequestContext.RouteData.Values["controller"].ToString();
                string action = Request.RequestContext.RouteData.Values["action"].ToString();

                //We clear the response
                Response.Clear();
                Server.ClearError();

                // Validate the this controller is legit

                // If the controller exist, use it, or else use the error controller
                if (controller != null)
                    routeData.Values.Add("controller", controller);
                else
                    routeData.Values.Add("controller", "Error");

                // A good location for any error logging, otherwise, do it inside of the error controller.

                //We check if we have an AJAX request and return JSON in this case
                if (IsAjaxRequest())
                {
                    Response.Write("Your JSON here");
                }
                else
                {
                    if (httpException != null)
                    {
                        int httpCode = httpException.GetHttpCode();
                        switch (httpCode)
                        {
                            case 500:
                                Response.StatusCode = 404;
                                Response.ContentType = "text/html";
                                routeData.Values.Add("action", "Page500");

                                // Clear the error, otherwise, we will always get the default error page.
                                Server.ClearError();
                                break;

                            case 404:
                                Response.StatusCode = 404;
                                Response.ContentType = "text/html";
                                routeData.Values.Add("action", "Page404");

                                // Clear the error, otherwise, we will always get the default error page.
                                Server.ClearError();
                                break;

                            default:
                                Response.StatusCode = 404;
                                Response.ContentType = "text/html";
                                routeData.Values.Add("action", "Page404");

                                // Clear the error, otherwise, we will always get the default error page.
                                Server.ClearError();
                                break;
                        }

                        // We can pass the exception to the Action as well, something like
                        // routeData.Values.Add("error", exception);                        

                        // Call the controller with the route
                        IController errorController = new coastEnviromental.Controllers.ErrorController();
                        try
                        {
                            Response.TrySkipIisCustomErrors = true;
                            errorController.Execute(new RequestContext(new HttpContextWrapper(Context), routeData));
                        }
                        catch (Exception ex)
                        {
                            Console.WriteLine(ex.ToString());
                            Response.Redirect("Error");
                        }
                    }
                }                

            }
        }

public class ErrorController : Controller
    {
        public ActionResult Index()
        {
            return View();
            return View("Page404", "Error"); // Also tried
        }

        public ActionResult Page404()
        {
            return View();
        }

        public ActionResult Page500()
        {
            return View();
        }
    }