无法解决注册时抛出的异常错误

Question

I'm working on a registration right now, where if a user puts that they are under 18 years old - a error will come up after they submit their registration, saying You must be at least 18 years of age. but I keep getting this exception error thrown at the call stack in the submit table, saying the string was not recognized as a valid . I have put in BirthDate.Text = DateTime.Now.ToString("dd/MM/yyyy"); to attempt and fix the solution, but the error still comes up as a exception. Could I be missing something?

The error in question is

if (DateTime.Parse(BirthDate.Text).AddYears(18) > DateTime.Now) {
                errorList.Add("You must be at least 18 years of age.");

The code

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace website {
    public partial class Register : Page {

        string ConnectionString = "Server=localhost\\SQLEXPRESS;Database=HC;Trusted_Connection=True;";

        protected void Page_Load(object sender, EventArgs e) {

             BirthDate.Text = DateTime.Now.ToString("dd/MM/yyyy");

            if (!IsPostBack) {
                string QueryString = "select * from home";

                SqlConnection myConnection = new SqlConnection(ConnectionString);
                SqlDataAdapter myCommand = new SqlDataAdapter(QueryString, myConnection);
                DataSet ds = new DataSet();
                myCommand.Fill(ds, "House");

            }
        }

        protected void submit(object sender, EventArgs e) {

            List<string> errorList = new List<string>();

            if (BirthDate.Text == "") {
                LiteralControl birthDate = new LiteralControl("Birth date is required!");
                BirthDateRequired.Controls.Add(birthDate);
                errorList.Add(birthDate.Text);
            }

            if (DateTime.Parse(BirthDate.Text).AddYears(18) > DateTime.Now) {
                errorList.Add("You must be at least 18 years of age.");
            }

            if (errorList.Count > 0) {
                foreach (string s in errorList)
                    ErrorList.Controls.Add(new LiteralControl("* " + s));
            }

        }
    }
}

Answer 1

You can use the following overload of ParseExact method instead -

public static DateTime ParseExact(string s, string format, IFormatProvider? provider);

where you can pass your intended date format as a string to the second parameter.

So, if your BirthDate.Text is taking input in dd/MM/yyyy format, then change the code to -

if (DateTime.ParseExact(BirthDate.Text, "dd/MM/yyyy", null).AddYears(18) > DateTime.Now)
{
    errorList.Add("You must be at least 18 years of age.");
}

Also, you don't need to set BirthDate.Text = DateTime.Now.ToString("dd/MM/yyyy");