{***************************************************************}
{ }
{ Siow写的第一个控件 }
{ }
{用途：主要用于数据录入界面 }
{特点：用选择代替输入，减少人工录入时的低级错误 }
{版本：V1.1 }
{ }
{ }
{***************************************************************}

程序代码如下所示：

unit DBLookUpEdit;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, Grids, DBGrids, StdCtrls, DB, ADODB;
//,ADOReg,DesignIntf,DesignEditors
type

{TDBLookUpEdit}

TDBLookUpEdit = class(TEdit)
private
FCreating: Boolean;
FKeyField: WideString;
FDBGrid : TDBGrid;
FADOQuery: TADOQuery;
FDataSource: TDataSource;
FOnEnter: TNotifyEvent;
FOnExit: TNotifyEvent;
FOnChange: TNotifyEvent;
//FOnClick: TNotiFyEvent;
//FOnDblClick:TNotifyEvent;
procedure CNCommand(var Message: TWMCommand);
message CN_COMMAND;
function GetActive: Boolean;
procedure SetActive(Value: Boolean);
function GetDataSource: TDataSource;
procedure SetDataSource(Value: TDataSource);
function GetConnectionString: WideString;
procedure SetConnectionString(const Value: WideString);
function GetConnection: TADOConnection;
procedure SetConnection(const Value: TADOConnection);
function GetSQL: TStrings;
procedure SetSQL(const Value: TStrings);
procedure SetRecText(FieldNo: integer);
procedure DoFDBGridMouseUp(Sender: TObject; Button: TMouseButton;Shift: TShiftState; X, Y: Integer);
procedure DoFDBGridKeyDown(Sender: TObject; var Key: Word;Shift: TShiftState);
protected
procedure SetParent(AParent: TWinControl); override;
procedure Notification(AComponent: TComponent; Operation: TOperation); override;
procedure CMVisiblechanged(var Message: TMessage);
message CM_VISIBLECHANGED;
procedure CMEnabledchanged(var Message: TMessage);
message CM_ENABLEDCHANGED;
procedure CMBidimodechanged(var Message: TMessage);
message CM_BIDIMODECHANGED;
procedure FDoEnter(Sender: TObject);
procedure FDoExit(Sender: TObject);
procedure KeyDown(var Key: Word; Shift: TShiftState); override;
procedure KeyPress(var Key: Char); override;
procedure KeyUp(var Key: Word; Shift: TShiftState); override;
procedure Loaded; override;
procedure CreateWnd; override;
public
constructor Create(AOwner: TComponent); override;
procedure SetBounds(ALeft: Integer; ATop: Integer; AWidth: Integer; AHeight: Integer); override;

published
//procedure Click;override;
property KeyFieldName:WideString read FKeyField write FKeyField;
procedure DblClick; override;
property OnEnter: TNotifyEvent read FOnEnter write FOnEnter;
property OnExit: TNotifyEvent read FOnExit write FOnExit;
property OnChange: TNotifyEvent read FOnChange write FOnChange;
//property OnClick: TNotifyEvent read FOnClick write FOnClick;
//property OnDblClick: TNotifyEvent read FOnDblClick write FOnDblClick;
//property DataSource: TDataSource read GetDataSource write SetDataSource;
property Active: Boolean read GetActive write SetActive default False;
property ConnectionString: WideString read GetConnectionString write SetConnectionString;
property Connection: TADOConnection read GetConnection write SetConnection;
property SQL: TStrings read GetSQL write SetSQL;
end;

procedure Register;

implementation

{ TDBLookUpEdit }

procedure Register;
begin
  RegisterComponents('LD Controls', [TDBLookUpEdit]);
  //RegisterPropertyEditor(TypeInfo(WideString), TDBLookUpEdit, 'ConnectionString',     TConnectionStringProperty);
end;

constructor TDBLookUpEdit.Create(AOwner: TComponent);
begin
inherited;
FDBGrid :=TDBGrid.Create(Self);
FADOQuery :=TADOQuery.Create(self);
FDataSource :=TDataSource.Create(self);

FDBGrid.FreeNotification(self);
FADOQuery.FreeNotification(self);
FDataSource.FreeNotification(self);

FDataSource.DataSet:=FADOQuery;
with FDBGrid do
begin
DataSource:=FDataSource;
Ctl3D:=false;
Visible:=false;
ParentCtl3D:=false;
Options:=[dgColLines,dgRowLines,dgRowSelect,dgAlwaysShowSelection,dgConfirmDelete,dgCancelOnExit];
OnMouseUp:=DoFDBGridMouseUp;
OnKeyDown:=DoFDBGridKeyDown;
end;

with self do
begin
  ParentCtl3D:=false;
  Ctl3D:=false;
end;
end;

procedure TDBLookUpEdit.CreateWnd;
begin
  FCreating := True;
   try
  inherited CreateWnd;
  finally
  FCreating := False;
end;
end;

procedure TDBLookUpEdit.CMBidimodechanged(var Message: TMessage);
begin
  inherited;
   FDBGrid.BiDiMode := BiDiMode;
end;

procedure TDBLookUpEdit.CMEnabledchanged(var Message: TMessage);
begin
  inherited;
  FDBGrid.Enabled := Enabled;
end;

procedure TDBLookUpEdit.CMVisiblechanged(var Message: TMessage);
begin
  inherited;
end;

procedure TDBLookUpEdit.Notification(AComponent: TComponent;
Operation: TOperation);
begin
  inherited Notification(AComponent, Operation);
  if (AComponent = FDBGrid) and (Operation = opRemove) then FDBGrid:= nil;
  if (AComponent = FADOQuery) and (Operation = opRemove) then FADOQuery:= nil;
  if (AComponent = FDataSource) and (Operation = opRemove) then FDataSource:= nil;
end;

procedure TDBLookUpEdit.SetParent(AParent: TWinControl);
begin
  inherited SetParent(AParent);
  if FDBGrid <> nil then FDBGrid.Parent := self.Owner as TForm;
end;

procedure TDBLookUpEdit.SetBounds(ALeft, ATop, AWidth, AHeight: Integer);
begin
  inherited;
  if FDBGrid <> nil then
  with FDBGrid do
begin
  Top:=-Height;
  Left:=-Width;
end;
end;

procedure TDBLookUpEdit.SetRecText(FieldNo: integer);
begin
  self.SetFocus;
  self.SelectAll;
    if (FADOQuery.Connection <>nil) or (FADOQuery.ConnectionString <>'') then
    if FADOQuery.Active then
    if FADOQuery.RecordCount >0 then
    if FADOQuery.FieldCount>FieldNo then
begin
  self.Text:=FDBGrid.Fields[FieldNo].Text;
  self.SelectAll;
  self.SetFocus;
end;
end;

procedure TDBLookUpEdit.FDoEnter(Sender: TObject);
var
p :TPoint;
begin
  P:=self.ClientToParent(point(0,self.Height),(self.Owner as TForm));
  if (FDBGrid.Height+p.y+2)<=(self.Owner as TForm).Height then
begin
  FDBGrid.Top :=p.y+2;
end
  else begin
  FDBGrid.Top :=p.y-2-self.Height -FDBGrid.Height;
end;
  FDBGrid.Left :=p.x+2;
  FDBGrid.BringToFront;
  FDBGrid.Visible:=true;
if self.Text='' then SetRecText(1);
  self.SelectAll;
if (self.Text<>'') and FADOQuery.Active then
  FADOQuery.Locate(FKeyField, self.text,[lopartialkey]);
end;

procedure TDBLookUpEdit.FDoExit(Sender: TObject);
begin
  if not FDBGrid.Focused then FDBGrid.Visible:=false;
end;

procedure TDBLookUpEdit.DoFDBGridMouseUp(Sender: TObject;
Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
  SetRecText(1);
  FDBGrid.Visible:=false;
end;

procedure TDBLookUpEdit.DoFDBGridKeyDown(Sender: TObject; var Key: Word;
Shift: TShiftState);
begin
  if key=13 then
begin
   SetRecText(1);
    FDBGrid.Visible:=false;
   key:=0;
 end;
end;

procedure TDBLookUpEdit.CNCommand(var Message: TWMCommand);
begin
  case Message.NotifyCode of
  EN_CHANGE:
begin
  if not FCreating then
  if Assigned(FOnChange) then FOnChange(self);
end;
  EN_KILLFOCUS:
begin
  if Assigned(FOnExit) then FOnExit(self);
  FDoExit(self);
end;
  EN_SETFOCUS:
begin
  if Assigned(FOnEnter) then FOnEnter(self);
  FDoEnter(self);
  end;
 end;
end;

procedure TDBLookUpEdit.DblClick;
begin
  inherited;
  FDoEnter(self);
end;

function TDBLookUpEdit.GetDataSource: TDataSource;
begin
  Result := FDBGrid.DataSource;
end;

procedure TDBLookUpEdit.SetDataSource(Value: TDataSource);
begin
  if Value <> FDBGrid.Datasource then FDBGrid.DataSource := Value;
  if Value <> nil then Value.FreeNotification(Self);
end;

procedure TDBLookUpEdit.KeyDown(var Key: Word; Shift: TShiftState);
begin
  inherited;
  if FDBGrid.Visible then
begin
  if (key=38) or (key=40) then
begin
  SendMessage(FDBGrid.Handle,WM_KEYDOWN,key,0);
  key:=0;
  end;
    if key=13 then
   begin
    SetRecText(1);
     FDBGrid.Visible:=false;
     key:=0;
   end;
  end;
end;

//判断是否全是数字
function IsAllInteger(Text:widestring):boolean;
var
Temp:string;
i:integer;
begin
try
Result:=true;
Temp:=trim(text);
if (length(Temp)<=0) then
begin
  Result:=false;
  exit;
end;
for i:=1 to length(Temp) do
begin
  if not (Temp[i] in ['0'..'9']) then
    begin
     Result:=false;
    break;
  end;
end;
  except
   Result:=false;
  end;
end;

//生成筛选语句
function CSQL(EditText,FieldName:WideString):WideString;
var
i:integer;
sql:WideString;
tmEditText1,tmEditText2:WideString;
begin
  Result:='';
    if IsAllInteger(EditText) then
     begin
      tmEditText1:=trim(EditText);
      tmEditText2:=trim(EditText);
        SQL:=SQL+'('+FieldName+'>='+trim(EditText)+' and '+FieldName+'<='+inttostr((StrToInt(EditText) div 10)*10+9)+')';
    for i:=length(EditText) to 6 do
begin
   tmEditText1:=tmEditText1+'0';
   tmEditText2:=tmEditText2+'9';
      sql:=sql+' or ('+FieldName+'>='+tmEditText1+' and '+FieldName+'<='+tmEditText2+')';
    end;
   Result:=sql;
  end;
end;

procedure TDBLookUpEdit.KeyUp(var Key: Word; Shift: TShiftState);
begin
  inherited;
    if FDBGrid.Visible then
  begin
    if (key=38) or (key=40) then
  begin
   SetRecText(1);
  end
else if IsAllInteger(self.Text) then
begin
  FADOQuery.Filtered:=false;
  FADOQuery.Filter:=CSQL(self.Text,FKeyField);
  FADOQuery.Filtered:=true;
   end;
  end;
end;

procedure TDBLookUpEdit.KeyPress(var Key: Char);
begin
  inherited;
end;

function TDBLookUpEdit.GetConnection: TADOConnection;
begin
  Result := FADOQuery.Connection;
end;

procedure TDBLookUpEdit.SetConnection(const Value: TADOConnection);
begin
  if Value <> FADOQuery.Connection then
  begin
  FADOQuery.Connection := Value;
  end;
  if Value <> nil then Value.FreeNotification(Self);
end;

function TDBLookUpEdit.GetConnectionString: WideString;
begin
  Result := FADOQuery.ConnectionString;
end;

procedure TDBLookUpEdit.SetConnectionString(const Value: WideString);
begin
  if Value <> FADOQuery.ConnectionString then FADOQuery.ConnectionString := Value;
 end;

function TDBLookUpEdit.GetActive: Boolean;
begin
  Result :=FADOQuery.Active;
end;

procedure TDBLookUpEdit.SetActive(Value: Boolean);
begin
  if Value <> FADOQuery.Active then
  begin
    FADOQuery.Active := Value;
  end;
end;

function TDBLookUpEdit.GetSQL: TStrings;
begin
  Result := FADOQuery.SQL;
end;

procedure TDBLookUpEdit.SetSQL(const Value: TStrings);
begin
  if FADOQuery.SQL<>Value then FADOQuery.SQL.Assign(Value);
end;

procedure TDBLookUpEdit.Loaded;
begin
  inherited Loaded;
end;

end.