How can i convert a string number into integer for number size validation? I use my case as an example A 5 digi Unique number is input (14568) begin // To prevent Candidate Number longer than 4 digits and blank input if (length(Can_No.Text) > 4) or (Can_No.Text = '') then if (THE CODE I NEED TO ADD HERE) begin ShowMessage('Invalid Candidate Number'); // Error Message end first i validation the string's length and blank input, after that# I want to convert this string into numbers and validation against these statments: the number must be in range of 10000 to 80000 No A.. Z, a..z, all symbols THis is kinda urgently Thanks for any help Plz.

1. convert a string number into integer: You can use this function. ----> strtoint() ex: int num1; num1 := strtoint(Edit1.text); There is no error, if the value of Edit1.text is '12345' (it is a numeric). But the value of Edit1.text is '12a34' then Error. so.... 2. No A.. Z, a..z, all symbols: You should code this program in the OnKeyPress Event In Edit1. procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char); begin if pos(Key, '0123456789') = 0 then Key = #0; end; If the user types not 0~9 then the key is no value; 3. To check the number in range of 10000 to 80000: If you have already added onKeyPress Event that likes no.2, then the value of Edit1 is a numeric. So you can use the function strtoint() to change from a string of Edit1.text to a integer. ex: if trim(Edit1.text) <> '' then if (Strtoint(Edit1.text)) >= 10000) And (Strtoint(Edit1.text) <= 80000) Then Begin //To do something that you want to do! End; Then you can ignore this program 'if (length(Can_No.Text) > 4) or (Can_No.Text = '') then' finally.... My english is very poor, thanks for your read. ---------------- 快滿一年程設師， 日日工作寫程式， 每買樂透眼框溼， 望能早成系分師。 ----------------

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初出芧房程設師，
左鍵右鼠寫程式，
日扣夜寫眼框溼，
望能早成系分師。
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your english really is a little hard to understand.. and i am a little confuse too do u mind putting the code together for me? how should the code look like in complete form with all the validation statement included? thanks

Use error handle with StrToInt to examine if data is number.     

procedure TForm1.Button2Click(Sender: TObject);
var
  FData: integer;
  function IsNumeric(FValue: String): Boolean;
  begin
    try
      StrToInt(FValue);
      Result := true;
    except
      Result := false;
    end;
  end;
begin
  if IsNumeric(Edit1.Text) then
  begin
    FData := StrToInt(Edit1.Text);
    if (FData >= 10000) and (FData <= 80000) then
      ShowMessage('ok')
    else
      ShowMessage('invalid data');
  end
  else
    ShowMessage('invalid data');
end;

function IsNumeric(FValue: String): Boolean; begin try StrToInt(FValue); Result := true; except Result := false; end; end; Is this one standalone?

Also, I cannot fit this into another procedure.. procedure TStudents.Button4Click(Sender: TObject); begin // To prevent Candidate Number longer than 4 digits and blank input if (length(Can_No.Text) <> 4) or (Can_No.Text = '') then begin ShowMessage('Invalid Candidate Number'); // Error Message end else // To prevent Centre Number longer than 5 digits and blank input if (length(Centre_No.Text) <> 5) or (Centre_No.Text = '') then begin ShowMessage('Invalid Centre Number'); end {WHERE I PLACE YOUR SUGGEST CODING} else begin tStudent.Append; tStudent.FieldByName('CandidateName').AsString := Can_Name.Text; tStudent.FieldByName('CandidateNumber').AsString := Can_no.Text; tStudent.FieldByName('CentreNumber').AsString := Centre_No.Text; tStudent.FieldByName('CentreName').AsString := Centre_Name.Text; tStudent.Post; end; end; The function bit cannot fit into it

Add the red code into your program !!    

procedure TStudents.Button4Click(Sender: TObject);

  function IsNumeric(FValue: String): Boolean;
  begin
    try
      StrToInt(FValue);
      Result := true;
    except
      Result := false;
    end;
  end;    begin  // To prevent Candidate Number longer than 4 digits and blank input
  if (length(Can_No.Text) <> 4) or (Can_No.Text = '') or (not IsNumeric(Can_No.Text)) then
    begin
      ShowMessage('Invalid Candidate Number'); // Error Message
    end      else // To prevent Centre Number longer than 5 digits and blank input
  if (length(Centre_No.Text) <> 5) or (Centre_No.Text = '') or (not IsNumeric(Centre_No.Text)) then
    begin
      ShowMessage('Invalid Centre Number');
    end      else
    begin
      tStudent.Append;
      tStudent.FieldByName('CandidateName').AsString := Can_Name.Text;
      tStudent.FieldByName('CandidateNumber').AsString := Can_no.Text;
      tStudent.FieldByName('CentreNumber').AsString := Centre_No.Text;
      tStudent.FieldByName('CentreName').AsString := Centre_Name.Text;
      tStudent.Post;
    end;    end;