As this already has an incorrect solution here are my comments
If your datagridview has not been populated with databinding then you will need to blank out each cell in the row you want to clear. It's not hard though, and you don't need to know how many cells there are e.g.
foreach(DataGridViewCell cell in Dgv.Rows(Rno).Cells)
{
cell.Value = string.Empty;
}
You might want to experiment with cells of different types (e.g. dates, hyperlinks, checkboxes)
However, if your datagridview is databound then you will need to blank those values in the source - whatever that might be, and rebind the datasource to the datagridview. Without explicit detail on how you are populating the DGV I can't really give you more