Gridview get next and previous cells values

Question

How to get a gridview row previous and next cell value on rowdatabound event. I tried this

 

GridViewRow prevRow = GridView1.Rows[e.Row.RowIndex - 1];

Label previousValue = prevRow.FindControl("SLNO") as Label;

 

But it throws an error like this

 

Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index

 

Thanks