Marshalling complex objects across to a translator object in the interrogated process is not supported. If you want to update a single cell value use the grid's SetCellValue method.
The other option would be to modify the grid's DataSource directly. However, DataSource could be one of any number of types. You'd need to discern its actual type before proceeding. For instance, if the DataSource was a DataTable you could probably do something like.
Thanks for your effort. I and my team mate where able to find a way around.
We noticed that Pega only communicate well with wpf textboxes but fails when we try to pass message into wpf textblocks and labels.
We decided to use textbox in place of our label.
The trick was, we won't let Pega fetch the data but pass the sql connection string and command string to the interrogated hidden textboxes in the wpf application and perform a click event on a hidden button confirming that the textboxes have being filled with the sql statement required for fetching the data.
Once that is done, A method inside the WPF UI is triggered to fetch the data itself and bind it to it datagrid.