在保留字Try和Finally之間的代碼跟前面的代碼是一樣的，它們用於在記錄之間移動記錄指針並處理對記錄的修改，這一段代碼可能會出現異常，當異常發生時，我們想保證執行EnableControls，以便窗體中各控件恢復與 TTable 部件的聯系， 因此我們必須將EnableControls語句放在Finally和結束語句End之間。
在這裡要特別注意，請讀者們不要混淆了Try...Finally語句和Try...Except 語句。如果真正想在發生異常時采取相應的處理，就要使用Try...Except語句。Try... Finally語句只是用來處理當異常出現時，使應用程序執行Finally部分的語句，使程序繼續執行下去。Try...Except語句是實現異常處理，Try...Finally語句是實現異常保護。
有了上述這些概念，我們便可以提供這個例子的一些程序代碼，它涉及了所有這些內容。
程序清單：修改數據庫中的記錄
unit Unit26;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, Grids, DBGrids, ExtCtrls, DB, DBTables, Buttons;
type
TForm1 = class(TForm)
DataSource1: TDataSource;
customerTable: TTable;
Panel1: TPanel;
DBGrid1: TDBGrid;
Panel2: TPanel;
UpperCaseFirstAddBtn: TButton;
UpperCaseSecondAddBtn: TButton;
MixedCaseFirstAddBtn: TButton;
MixedCaseSecondAddBtn: TButton;
BitBtn1: TBitBtn;
procedure ForceCase(TargetFIEld:String;ToUpper:Boolean);
procedure UpperCaseFirstAddBtnClick(Sender: TObject);
procedure MixedCaseFirstAddBtnClick(Sender: TObject);
procedure UpperCaseSecondAddBtnClick(Sender: TObject);
procedure MixedCaseSecondAddBtnClick(Sender: TObject);
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
const
upper=true;
Mixed=False;
{$R *.DFM}
Function IsUpper(ch:char):Boolean;
begin
If (ch>='A')and(ch<='Z')then
IsUpper:=true
else
IsUpper:=False;
end;
procedure TForm1.ForceCase(TargetFIEld:String;ToUpper:Boolean);
var
WorkBuffer:string;
i:Integer;
begin
with customerTable do
begin
DisableControls;
TRY
First; {將記錄指針移到第一條記錄處 }
While not EOF do
begin
WorkBuffer:=FieldByName(TargetFIEld).AsString;
If ToUpper then
for i:=1 to Length(WorkBuffer)do
WorkBuffer[i]:=UpCase(WorkBuffer[i])
else
begin
for i:=1 to Length(WorkBuffer) do
If IsUpper(WorkBuffer[i]) then
WorkBuffer[i]:=chr(ord(WorkBuffer[i])+32);
WorkBuffer[1]:=UpCase(WorkBuffer[1])
end;
Edit;
FieldByName(TargetFIEld).AsString:=WorkBuffer;
post;
Next;
end;
Finally
enableControls;
end;
end;
end;
procedure TForm1.UpperCaseFirstAddBtnClick(Sender: TObject);
begin
ForceCase('Addr1',Upper);
end;
procedure TForm1.MixedCaseFirstAddBtnClick(Sender: TObject);
begin
ForceCase('Addr1',Mixed);
end;
procedure TForm1.UpperCaseSecondAddBtnClick(Sender: TObject);
begin
ForceCase('Addr2',Upper);
end;
procedure TForm1.MixedCaseSecondAddBtnClick(Sender: TObject);
begin
ForceCase('Addr2',Mixed);
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
customerTable.open;
end;
end.
