3.4.2. Connecting to the database

To connect to the database, it is necessary to change the Connected property of the TFDConnection component to True or call the Open method. You can use the Open method to pass the username and password as parameters.

A Little Modification

We will replace the standard database connection dialog box in our application and allow users to make three mistakes while entering the authentication information. After three failures, the application will be closed.

To implement it, we will write the following code in the OnCreate event handler of the main data module.

// After three unsuccessful login attempts, we close the application.
xLoginCount := 0;
xLoginPromptDlg := TLoginPromptForm.Create(Self);
while (xLoginCount < MAX_LOGIN_COUNT) and
      (not FDConnection.Connected) do
begin
  try
    if xLoginPromptDlg.ShowModal = mrOK then
      FDConnection.Open(
        xLoginPromptDlg.UserName, xLoginPromptDlg.Password)
    else
      xLoginCount := MAX_LOGIN_COUNT;
  except
    on E: Exception do
    begin
      Inc(xLoginCount);
      Application.ShowException(E);
    end
  end;
end;
xLoginPromptDlg.Free;
if not FDConnection.Connected then
  Halt;