如何在c#中从SQL检索日期和时间到datetimepicker？

Question

If I enter a value(already entered in DB) and click a button(Retrieve) in my windows form, I have to retrieve date and time to my datetimepicker1 from SQL(already entered values). Please correct my code. This is my code.

    private void button9_Click(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection("Data Source=NIFAL;Initial Catalog=LaundrySystem;Integrated Security=True;");
        con.Open();
        str = "select * from LaundrySystemTable where laundID='" + textBox1.Text.Trim() + "'";
        cmd = new SqlCommand(str, con);
        SqlDataReader reader = cmd.ExecuteReader();
        if (reader.Read())
        {
            string temp1 = reader["entryDate"].ToString();
            DateTime dt1 = DateTime.Parse(temp1);
            dateTimePicker1.Value = dt1.ToString("MM:dd:yyyy");
            reader.Close();
            con.Close();
        }
    }

Answer 1

NEVER use such an SQL that is open to SQL inkjection attacks, use parameters instead:

using (SqlConnection con = new SqlConnection("Data Source=NIFAL;Initial Catalog=LaundrySystem;Integrated Security=True;"))
{
  string sql = "select entryDate from LaundrySystemTable where laundID=@id";
  var cmd = new SqlCommand( sql, con );
  cmd.Parameters.AddWithValue( "@id", textBox1.Text.Trim() ); // if its type is not string, then do the conversion here
  con.Open();
  SqlDataReader reader = cmd.ExecuteReader();
  if (reader.Read())
  {
    dateTimePicker1.Value = (DateTime?)reader["entryDate"];
  }
  con.Close();
}