Synchronizing 2 grids via the CurrencyManager

[Pete Davis]

I have written a custom databound grid control that we've been using
successfully for months, but one of our developers has just run into a
problem that I can't figure out.

The code for setting it up is as follows:

DataSet dataSet = new DataSet( "TestSet" );

DataTable tableParent = dataSet.Tables. Add( "TableParen t" );
tableParent.Col umns.Add( "ID", typeof( Int32 ) );
tableParent.Col umns[ "ID" ].AutoIncrement = true;
tableParent.Col umns[ "ID" ].Unique = true;
tableParent.Col umns.Add( "Col1", typeof(Int32) );
tableParent.Col umns.Add( "Col2", typeof(Int32) );

DataTable tableChild = dataSet.Tables. Add( "TableChild " );
tableChild.Colu mns.Add( "ID", typeof( Int32 ) );
tableChild.Colu mns.Add( "Col1", typeof(Int32) );
tableChild.Colu mns.Add( "Col2", typeof(Int32) );

dataSet.Relatio ns.Add( "Child2Pare nt", tableParent.Col umns[ "ID" ],
tableChild.Colu mns[ "ID" ] ).Nested = true;

gridParent.Data Source = dataSet;
gridParent.Data Member = "TableParen t";
gridChild.DataS ource = dataSet;
gridChild.DataM ember = "TableParent.Ch ild2Parent";

The way it is supposed to work (and does work with the MS DataGrid) is that
when you select a row in the parent table, it should set the data in the
child table to all children of the selected parent.

In my grid, when the current cell changes, I set the position in the
CurrencyManager to the new position. My understanding (and apparently a
false one) was that the CurrencyManager would update the position in the
underlying dataset which in turn would then inform all CurrencyManager s
bound to it. Apparently that's not the case.

The parent grid receives the CurrencyManager .PositionChange d event but the
child grid receives no events from its CurrencyManager .

How am I supposed to propagate an update to the child grid?

Thanks.

Pete

[Pete Davis]

Okay, after digging through DataGrid, BindingContext, CurrencyManager and
RelatedCurrency Manager, I have a much better idea of how it's supposed to
operate, but I still haven't solved the problem.

Both the parent and child grids are getting RelatedCurrency Manager objects
from the BindingContext because they both have DataMember set, and as far as
I can tell, this is correct. The parent grid's RelatedCurrency Manager is the
parent of the child grid's RelatedCurrency Manager.

The child RelatedCurrency Manager is subscribing to the CurrentChanged of the
parent. Now, I know the parent CurrentChanged is getting called, because I
subscribe to it in my grid.

In RelatedCurrency Manager.ParentM anager_CurrentC hanged, a call is made to
this.SetDataSou rce() which should trigger calls to ItemChanged and
PositionChanged in the child grid's RelatedCurrency Manager, which the child
grid subscribes to, but these aren't getting called.

I'm just stumped.

Pete
"Pete Davis" <pd******@NOSPA M.hotmail.com> wrote in message
news:e-*************** *****@giganews. com...

I have written a custom databound grid control that we've been using
successfully for months, but one of our developers has just run into a
problem that I can't figure out.

The code for setting it up is as follows:

DataSet dataSet = new DataSet( "TestSet" );

DataTable tableParent = dataSet.Tables. Add( "TableParen t" );
tableParent.Col umns.Add( "ID", typeof( Int32 ) );
tableParent.Col umns[ "ID" ].AutoIncrement = true;
tableParent.Col umns[ "ID" ].Unique = true;
tableParent.Col umns.Add( "Col1", typeof(Int32) );
tableParent.Col umns.Add( "Col2", typeof(Int32) );

DataTable tableChild = dataSet.Tables. Add( "TableChild " );
tableChild.Colu mns.Add( "ID", typeof( Int32 ) );
tableChild.Colu mns.Add( "Col1", typeof(Int32) );
tableChild.Colu mns.Add( "Col2", typeof(Int32) );

dataSet.Relatio ns.Add( "Child2Pare nt", tableParent.Col umns[ "ID" ],
tableChild.Colu mns[ "ID" ] ).Nested = true;

gridParent.Data Source = dataSet;
gridParent.Data Member = "TableParen t";
gridChild.DataS ource = dataSet;
gridChild.DataM ember = "TableParent.Ch ild2Parent";

The way it is supposed to work (and does work with the MS DataGrid) is that when you select a row in the parent table, it should set the data in the
child table to all children of the selected parent.

In my grid, when the current cell changes, I set the position in the
CurrencyManager to the new position. My understanding (and apparently a
false one) was that the CurrencyManager would update the position in the
underlying dataset which in turn would then inform all CurrencyManager s
bound to it. Apparently that's not the case.

The parent grid receives the CurrencyManager .PositionChange d event but the
child grid receives no events from its CurrencyManager .

How am I supposed to propagate an update to the child grid?

Thanks.

Pete