TClientDataSet Missing Data Provider

Question

This question does not have any code, but I must ask for help because I can not resolve this issue. I searched SO for similar questions and found several whose answers did not help me resolve this problem.

I was having trouble creating a TClientDataSet project with my main development pc, so I tried creating a project on my Windows Tablet. Both pcs are running windows 8.1 with DelphiXE4.

I added a TClientDataSet, a TDataSource and a TDatasetProvider to a new project. I added 3 fields in FieldDefs at design time, then selected CreateDataset from the popupmenu of TClientDataSet. The dataset was created just fine so I continued and added a TDBGrid, TDBNavigator, entered some data and saved the TClientDataSet to a file.

The small demo app worked very well with no problems. I can view and enter data, save to a file and load from a file, so I zipped up the project and copied it to my development pc. I tried running the demo but when LoadFromFile is called a Missing Data provider exception occurs. I tried deleting the xml file and then tried to recreate the file using the same process I used on the tablet pc and I got the Missing Data provider message again.

In following up on the SO answers I added MidasLib to uses as recommended in several SO answers but that failed to resolve the problem. I searched for Midas.DLL and found them to be present.

My question: Is it possible that dsnap180.bpl is corrupt or is something else missing from my development pc? My objective is to be able to create and open a TClientDataset on my development pc. Any suggestions or guidance is appreciated.

EDIT Kens Demo

Pas

    unit Unit1;

    interface

    uses
      Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
      System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.Grids,
      Vcl.DBGrids, Data.DB, Datasnap.DBClient;

    type
      TForm1 = class(TForm)
        ClientDataSet1: TClientDataSet;
        DataSource1: TDataSource;
        DBGrid1: TDBGrid;
        procedure FormCreate(Sender: TObject);
      private
        { Private declarations }
      public
        { Public declarations }
      end;

    var
      Form1: TForm1;

    implementation

    {$R *.dfm}

    procedure TForm1.FormCreate(Sender: TObject);
    begin
      ClientDataSet1.FieldDefs.Add('Collection', ftString, 50);
      ClientDataSet1.FieldDefs.Add('Filename', ftString, 200);
      ClientDataSet1.CreateDataSet;
      ClientDataSet1.Active := True;
      ClientDataSet1.AppendRecord(['General', 'D:\Images\Test.jpg']);
      ClientDataSet1.AppendRecord(['General', 'D:\Images\BeachBall.bmp']);
    end;
end.

DFM

object Form1: TForm1
      Left = 0
      Top = 0
      Caption = 'Form1'
      ClientHeight = 299
      ClientWidth = 635
      Color = clBtnFace
      Font.Charset = DEFAULT_CHARSET
      Font.Color = clWindowText
      Font.Height = -11
      Font.Name = 'Tahoma'
      Font.Style = []
      OldCreateOrder = False
      OnCreate = FormCreate
      PixelsPerInch = 96
      TextHeight = 13
      object DBGrid1: TDBGrid
        Left = 0
        Top = 0
        Width = 635
        Height = 299
        Align = alClient
        DataSource = DataSource1
        TabOrder = 0
        TitleFont.Charset = DEFAULT_CHARSET
        TitleFont.Color = clWindowText
        TitleFont.Height = -11
        TitleFont.Name = 'Tahoma'
        TitleFont.Style = []
      end
      object ClientDataSet1: TClientDataSet
        Aggregates = <>
        Params = <>
        Left = 71
        Top = 35
      end
      object DataSource1: TDataSource
        DataSet = ClientDataSet1
        Left = 116
        Top = 34
      end
    end

DPR program Project1;

uses
  Vcl.Forms,
  Unit1 in 'Unit1.pas' {Form1};

{$R *.res}

begin
  Application.Initialize;
  Application.MainFormOnTaskbar := True;
  Application.CreateForm(TForm1, Form1);
  Application.Run;
end.

If you're editing your q to follow Ken White's suggestion, one extra thing you might do is to add your saved XML data file to your q. Then we can try to just load it and see what behaviour we get in a zero code project. — MartynA
I know this exception if you open/activate the dataset without a created dataset and no filename set. — Sir Rufo
I can not add the xml file to the edit because the app never creates the database as that is where the exception occurs, — Bill
Copying/pasting the above into files on my machine, compiling them and running them works perfectly (both in D2007 and XE6), and I can see data in the grid. I'd suspect you have something gone wrong in your Delphi installation somehow. — Ken White

Ken White Ken White · Accepted Answer · 2014-10-25T17:07:57

The following works for me perfectly well:

Drop a TClientDataSet, TDataSource, and TDBGrid on a blank form. Connect the grid to the datasource, and the datasource to the clientdataset. (Note no TDataSetProvider.)

Add the following code to the form's FormCreate event:

procedure TForm1.FormCreate(Sender: TObject);
begin
  ClientDataSet1.FieldDefs.Add('FirstName', ftString, 20);
  ClientDataSet1.FieldDefs.Add('LastName', ftString, 20);
  ClientDataSet1.CreateDataSet;
  ClientDataSet1.Active := True;
  ClientDataSet1.AppendRecord(['John', 'Smith']);
  ClientDataSet1.AppendRecord(['Jane', 'Doe']);
end;

Run the application:

Image with grid displaying data

Adding MidasLib to the uses clause removes the need to distribute Midas.dll with your application, but it does not affect the dataset provider at all.

TClientDataSet Missing Data Provider

2 Answers