How do I check if user input is in data file C# and display correct message?

Question

This is the data file named "ChargeAccounts.txt". I need to search this data file for a users account number entered in the textbox txtAccount.

---

 5658845
 4520125
 7895122
 8777541
 8451277
 1302850
 8080152
 4562555
 5552012
 5050552
 7825877
 1250255
 1005231
 6545231
 3852085
 7576651
 7881200
 4581002

---

I need to accomplish this using this array.

    const int SIZE = 18;
    string[] acct = new string[SIZE];

---

This is the code I have and it will only display "Account is invalid." even when I enter a account number from the data file.

    private void FindAccountNumber()
    {
       System.IO.StreamReader file =
       new System.IO.StreamReader("ChargeAccounts.txt");

        acct = File.ReadAllLines("ChargeAccounts.txt");


        for (int i = 0; i < acct.Length; i++)
        {

            if (txtAccount.Text.Contains(acct[i]))
            {
                lblMessage.Text = "Account is valid";
            }
            else
            {
                lblMessage.Text = "Account is invalid.";
            }
        }

      file.Close();
   }

Answer 1

You are iterating over all elements and updating lblMessage.Text for every iteration. So, you can get valid state only if txtAccount.Text contains last number in the file. You should break the for statement when valid number found, it will look like this

string message = "Account is invalid.";
for (int i = 0; i < acct.Length; i++)
{
    if (txtAccount.Text.Contains(acct[i]))
    {
        message = "Account is valid";
        break;
    }
}
lblMessage.Text = message;