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Posted on 2002-04-02
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Last Modified: 2010-04-04
I am creating a multi user MDI application.

I have created datamodules for database connection.

when i open two instance of same screen they show me the same record because they are reffering to the same recordset.

What shall i do to have different instanse of database connection for different instance of MDI child screens.

Regards

Mahesh
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Question by:princemahesh
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5 Comments
 
LVL 2

Expert Comment

by:isstorr
ID: 6912394
If you use a TADOTable for instance on a datamodule, you will get a common connection. Instead try creating your database components on the fly at runtime for each MDI instance -

type
  TMyMDIClass = class(TForm);
  private
   FTable: TADOTable
  public
  constructor Create; override;
  destructor Destroy;
  end;

constructor Create;
begin
 inherited;
 FTable := TADOTable.Create(self);
.
.
.
end;

destructor Destroy;
begin
 FTable.Free;
 inherited;
end;

You can use a common ADOConnection (though you can also give each instance its own connection as well if you wish) but this will ensure that each instance has its own dataset.

Si
0
 
LVL 10

Expert Comment

by:Jacco
ID: 6922592
Hi there,

The way I see it you need a DataModule for the database connection (with the TSession and TDataBase components) call it datMainConnection. And for every MDI Instance you can create a separate datamodule with DataSets on it which you connect to the TDataBase on the datMainConnection. This way you'll have one set of DataSets per MDI.

DataSources should go on the MDI Child itself. And you have to connect the datasources to the DataSets on the datMDIdata manually (for example in the FormCreate or the constructor).

When I use this technique I always have the datMDIdata created in the constructor of the MDIChild and store it in a private field.

This way you only have one TDataBase component (not wasting connection licenses and resources).

Regards Jacco
0
 
LVL 2

Accepted Solution

by:
isstorr earned 50 total points
ID: 6924860
BDE TTable/TDataSet equivalent of my earlier post -

type
 TMyMDIClass = class(TForm); // TDataModule or even TComponent if you prefer.
 private
  FTable: TTable;
  FDataSource: TDataSource;
 public
 constructor Create; override;
 destructor Destroy;
 end;

constructor Create;
begin
inherited;
FTable := TTable.Create(self);
FDataSource := TDataSource.Create(self);
FDataSource.DataSet := FTable;
.
.
.
end;

destructor Destroy;
begin
FDataSource.Free;
FTable.Free;
inherited;
end;
0
 
LVL 1

Expert Comment

by:Moondancer
ID: 6975947
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Expert Comment

by:pnh73
ID: 9002799
No comment has been added lately, so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area that this question is:

Accept Answer from isstorr

Please leave any comments here within the next seven days.
 
PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER!
 
Paul (pnh73)
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