private void btnSubmit_Click(object sender, RoutedEventArgs e) { //https://www.youtube.com/watch?v=RJvKaHPc8Dc DB_128040_practiceEntities db = new DB_128040_practiceEntities(); //string output = $"{Customer.FirstName}/{Customer.LastName}/{Customer.ID}"; if (int.TryParse(txtBoxInput.Text, out int CustomerID) == true) { int custID = Convert.ToInt32(txtBoxInput.Text); List <Customer> c = new List <Customer>(); foreach (var x in db.Customers) { if (x.CustomerID == custID) { listBoxCustomer.Items.Add(x); } } } else { string city = txtBoxInput.Text; //listBoxCustomer.Items.Add(output); } }