How do I mark a DataTable as read-only

[Philippe Bertrand]

I want to return a read-only DataTable so that I can cache it. Is it
possible?

Alternate suggestions (that don't waste tonnes of memory)?

Thanks,
Philippe

 

[William Ryan eMVP]

You can create it as a property of a class that's a readonly property. Or
you could set the columns to readonly. However I'm not sure what you mean
by "so you can cache it". It's cached in memory regardless. The size of the
table will dictate how much space it consumes.

--

W.G. Ryan, eMVP

http://forums.devbuzz.com/
http://www.knowdotnet.com/williamryan.html
http://www.msmvps.com/WilliamRyan/

 

[Philippe Bertrand]

I want to supply users with a GetInfoTable() method that returns some
information that will not change during the lifetime of the object it is
called on. I want something like:

class MyClass
{
private DataTable _info;

public DataTable GetInfoTable()
{
if( _info == null ) {
_info = new DataTable();
// build the table up
}
return _info;
}
}

Since the user receives a reference, I don't want any accidental calls to
Clear() or Reset() or user invoked Dispose() (via using() directive, etc).
Obviously, it should delete the data when garbage collected - i.e.
Dispose( false ).

// user code
using( DataTable dt = myClass.GetInfoTable() ) {
dt.Clear(); // does nothing
dt.Reset(); // does nothing
// user can't add rows
} // not really disposed

Philippe
P.S. Does DataTable.Reset() go back to the state after EndInit() or
EndLoad() or does it completely clean out the DataTable ?

 

[William Ryan eMVP]

You can create the object as a property that's read only and just manipulate
it from within the class (this will be somewhat limited - or you can
override some of those events. If I understand you though, it's going to be
pretty cumbersome adding all of that code.

--

W.G. Ryan, eMVP

http://forums.devbuzz.com/
http://www.knowdotnet.com/williamryan.html
http://www.msmvps.com/WilliamRyan/

 

[Philippe Bertrand]

How does a read only property help? All that means is that the user can
change the reference (pointer) - once the user has a reference, he can
change the contents.

I'm following another api so I must return a DataTable. I can't hide it
(private with accessor methods). Deriving from DataTable isn't an option
because there are too many holes (Column collection can add/remove columns,
etc).

I guess it will have to be a feature request that you can lock/freeze a
DataTable.

Philippe