Reading and writing .accdb file from DataModule in Delphi - database

Question

I am making a school project which consists of creating a database and reading and writing into it. Within a DataModule I made the database in run time using a TAdoCommand which worked great and now I need to read and write into it. I placed some test data into the database using access but it is unable to read the database.
DataModule Here is a picture of the datamodule in design. I have created a connection, query, datasource and table which are all linked together. The TAdoCommand was used to make the database. The SQL command in the query is "SELECT Username,Password
FROM Users"
I then have a Login form in which I hope to use it to read the Users table with the database to check if the user exists in the database.
procedure TLoginFrm.LoginBtnClick(Sender: TObject);
var Username, Password : String;
i, NoOfRecords : Integer;
IsMatch : Boolean;
begin
NoOfRecords := modFile.adoDataSet.RecordCount;
if NoOfRecords = 0 then
begin
NewUserFrm.Show;
Application.Messagebox('There are currently no users. Please create new user.','Error');
UsernameBox.Text := '';
PasswordBox.Text := '';
end
else
begin
IsMatch := False;
modFile.adoDataSet.First;
Username := modFile.adoDataSet.FieldByName('Username').AsString;
Password := modFile.adoDataSet.FieldByName('Password').AsString;
for i := 1 to NoOfRecords do
begin
if (Username = UsernameBox.Text) and (Password = PasswordBox.Text) then
begin
LoginFrm.Hide;
CurrentUser := Username;
MainMenuFrm.Show;
IsMatch := True;
end
else
begin
modFile.adoDataSet.Next;
Username := modFile.adoDataSet.FieldByName('Username').AsString;
Password := modFile.adoDataSet.FieldByName('Password').AsString;
end;
end;//End of for loop
if not IsMatch then
begin
Application.MessageBox('Incorrect username or password. Try again.','Error');
UsernameBox.Text := '';
PasswordBox.Text := '';
LoginBtn.SetFocus;
end;
end;//End of parent Else
end;
When I put in test data using Access, it returns the message box "Incorrect username or password. Try again". So it recognises that there are more than 0 reccords in the table however it cannot read the actual data. Where did I go wrong?

Answer 1

You're For loop isn't working for you here. Instead you need to iterate your dataset this way:
else
begin
isMatch := false;
modFile.AdoDataset.first;
while not modFile.AdoDataset.eof do
begin
Username := modFile.AdoDataset.fieldbyname('Username').asstring;
Password := modFile.AdoDataset.fieldbyname('Password').asstring;
if (uppercase(Username) = uppercase(UsernameBox.text)) and (uppercase(Password) = uppercase(PasswordBox.text)) then
begin
IsMatch := True;
LoginFrm.Hide;
CurrentUser := Username;
MainForm.Show;
Exit; // no need to continue on once you have a match
end;
modFile.AdoDataset.next;
end;
end
else ...
You could also skip using a loop altogether and just use a locate
else
begin
isMatch := modFile.AdoDataset.Locate('Username;Password', VarArrayOf[UsernameBox.text, PasswordBox.text], [loCaseInsensitive]);// remove loCaseInsensitive if you prefer case sensitivity
if isMatch then
begin
CurrentUser := UsernameBox.text;
Loginfrm.Hide;
MainForm.Show;
end;
end;