Frequently Asked Questions

Single Tier Applications

Question:

How do I set up a single tier application using Client
Datasets?

Answer:

Currently, the only way to activate a client dataset at

design time is to associate it with a provider, to load

data from a file, or to assign data from another dataset.

Typically, for a single tier application you would create

the dataset at runtime using the CreateDataSet method.

Here is how you might code the FormCreate and FormDestroy

methods:



OnFormCreate:



if FileExists('MYDATA.CDS') then

   ClientDataSet.LoadFromFile('MYDATA.CDS') 

else

begin

  ClientDataSet.FieldDefs.Add('Field1', etc.); 

  ClientDataSet.FieldDefs.Add('Field2', etc.);

  ClientDataSet.CreateDataset;

end;



OnFormDestroy:



if ClientDataSet.Active then

begin

  // Next line is optional, 

  // if you don't want undo support you could

  // set LogChanges = False instead.

  ClientDataSet.MergeChangeLog; 

  ClientDataSet.SaveToFile('MYDATA.CDS');

end;



Once you've run the app once and created the data file,

you can easily load it at design time (from the

right-click component menu) if you need to have the

dataset active at design time for some reason.