TCustomClientDataSet.CreateDataSet Method

Creates a new, empty client dataset.

Pascal

procedure CreateDataSet;

C++

__fastcall CreateDataSet();

Description

Call CreateDataSet at runtime to create a new, empty client dataset that can then be edited and saved.

If the FieldDefs property contains values, these values are used to create field definitions. Otherwise the Fields property is used. One or both of these properties must contain values in order to create a dataset. If neither property is set, CreateDataSet raises an exception.

If the IndexDefs property contains values, these values are used to create indexes for the dataset. Indexes created from the IndexDefs property are saved with the client dataset when it is saved to a file.

Note: You can create a dataset at design time as well: Create persistent field components or field definitions. Then right-click the client dataset and select Create Data Set.

C++ Examples:

Copy Code

/*
The following code creates and activates a client dataset in
the form’s OnCreate event handler.
*/ 
void __fastcall TForm1::FormCreate(TObject *Sender)
{
  TFieldDefs *pDefs = CDS2->FieldDefs;
  TFieldDef *pDef = pDefs->AddFieldDef();
  pDef->DataType = ftInteger;
  pDef->Name = "Field1";

  pDef = pDefs->AddFieldDef();
  pDef->DataType = ftString;
  pDef->Size = 10;
  pDef->Name = "Field2";

  TIndexDef *pIDef = CDS2->IndexDefs->AddIndexDef();
  pIDef->Fields = "Field1";
  pIDef->Name = "IntIndex";

  CDS2->CreateDataSet();
}

Delphi Examples:

Copy Code

{
This example requires two ClientDataSets, two DBGrids, two
DataSources and two DBNavigators.  Name the two
ClientDataSets CDS and CDS2. Set the DataSet property in the
first DataSource to CDS and name that DataSource DS.  Set the
DataSet property in the second DataSource to CDS2 and name
that DataSource DS2.  Set the DataSource in the first
DBNavigator to DS and the DataSource in the second DBNavigator
to DS2.  Set the DataSource in the first DBGrid to DS and the
DataSource in the second DBGrid to DS2.  Right click on CDS
and select the Fields Editor, then right click on the Field
Editor form and create two fields by selecting "new field".
In the field configuration window, set the name to HOST, the
Component value will automatically be set to CDSHOST.  Set
the filed type to String.  In the field configuration window
for the second field, set the name to PORTA, the Component
value will automatically be set to CDSPORTA.  Set the field
type to Integer.  The file used to load CDS must have an
attribute name of HOST with an attribute type of string and
an attribute name of PORTA with an attribute type of integer.
Add DB, DBCtrls, Grids, DBGrids, DBClient and SwSystem to the
uses clause.  "LoadFormFile" to start with the file, or 
"CreateDataSet" to start from scratch.  You must "CloseDataSet"
after a "LoadFromFile" before you can do another "CreateDataSet".
}
procedure TForm1.Button1Click(Sender: TObject);
begin
  CDS.LoadFromFile(gsAppPath + 'CDS.XML');
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  CDS.SaveToFile(gsAppPath + 'CDS.XML', dfXML);
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
  CDS.CreateDataSet;
end;

procedure TForm1.Button4Click(Sender: TObject);
begin
  CDS2.Data := CDS.Data;
end;

procedure TForm1.Button5Click(Sender: TObject);
begin
  CDS.Close;
end;

Copy Code

{
The following code creates and activates a client dataset in
the form’s OnCreate event handler.
} 
procedure TForm1.FormCreate(Sender: TObject);
begin
  with CDS2 do
  begin
    with FieldDefs.AddFieldDef do
    begin
      DataType := ftInteger;
      Name := 'Field1';
    end;
    with FieldDefs.AddFieldDef do
    begin
      DataType := ftString;
      Size := 10;
      Name := 'Field2';
    end;
    with IndexDefs.AddIndexDef do
    begin
      Fields := 'Field1';
      Name := 'IntIndex';
    end;
    CreateDataSet;
  end;
end;