protected void btnCheck_Click(object sender, EventArgs e) { SQL sql = new SQL(); try { Guid gu = new Guid(key.Value.Trim().ToString()); bool hasTaken = sql.checkIFTaken(gu); if (hasTaken) { string name = sql.CheckCandidate(gu); if (name == null) { throw new NullReferenceException(); } int allowed_time = sql.getAllowedTime(gu); time.InnerText = allowed_time.ToString() + " Minutes"; Username.Value = name; if (error.Visible == true) { error.Visible = false; complete.Visible = true; key.Disabled = true; } else { complete.Visible = true; key.Disabled = true; } } else { if (complete.Visible == true) { complete.Visible = false; error.Visible = true; error.InnerText = "It looks like you have already taken this test!"; } else { error.Visible = true; error.InnerText = "It looks like you have already taken this test!"; } } } catch(NullReferenceException){ if (complete.Visible == true) { complete.Visible = false; error.Visible = true; } else { error.Visible = true; } } catch (Exception) { if (complete.Visible == true) { complete.Visible = false; error.Visible = true; } else { error.Visible = true; } } }