It appears as though you are trying to update a dataset with a single
adapter, that is not how it is supposed to work.
If you setting the datasource of the datagrid to a datatable (part of a
dataset). Then all you have to do is update the datatable, you don't even
need to read the values from the grid to do it.

example:

class temp

public readonly property daTable as dataadapter

   dim objcmdBuilder as commandbuilder
   dim objdaTable as dataadataper
   dim objConn as dataconnection

   objConn = new dataconnection = "someconnnectrionstring"

   objdaTable = new dataadapter("SomeSelectStatement",objConn)
  objcmdBuilder = new commandbuilder(objdaTable)

  return objdaTable

end property

end class

class Form1

private m_CTemp as Temp

sub UpdateData()
   'I do not pretend to know what is in the webcontrol for a datagrid
   'I imagine that is is still the same as what is in the winform control

   dim dt as Datatable

   'Get all the changes from last postback
   dt = ctype(datagrid1.datasource, datatable).getchanges(added, updated,
deleted)

   'Apply them to the repository
   if not dt is nothing then  m_CTemp.dsTable.update(dt)

end sub

end Class

I know you are using c#, I hope you can get the just of what I am doing from
my VB sample.

hope that helps.