Hi,
Base on my understanding, you want to implement master-details on the form.
Assume you use datatables as dataSource and dataGridView to show data. Add the two datatables to a dataset and create relationship between two tables. The master dataGridView is bound to the dataset, datamember is the master datatable. The details datagridview is also bound the dataset, datamember need to be set to the relationship name. This will change the details data with your chosen master data.
One Faq tells about this:
31. How do I show master-details?
http://social.msdn.microsoft.com/Forums/en-US/winformsdatacontrols/thread/a44622c0-74e1-463b-97b9-27b87513747e#faq31
Best regards,
Ling Wang
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