I have a dataset which contains a single row. How can I insert that row into a selected row of data grid view which contains several rows.

Basically you have two ways of filling a grid view.

1.
You add item per item (or row per row). In that case you manually control the grid and you're able to add/remove/update rows as you wish.
Look here[^] for starters.

2.
You set the DataSource (winforms) or DataContext (WPF) object. In that case you're not able to freely control the grid anymore. You'll need to pass through the object that set the DataSource/Context by or modifying it, or by setting it again (after a reload eg.).
DataContext[^]
DataSource[^]

Hope this helps.