For that you have to add attribute mouserover and mouseout of Gridview row.

You can assign this attribute on OnRowDataBound

Event of gridview.

Code Snippet:

.aspx code:

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"

DataSourceID="SqlDataSource1" OnRowDataBound="bound" BackColor="Silver"

onselectedindexchanged="GridView1_SelectedIndexChanged" >

<Columns>

<asp:BoundField DataField="date" HeaderText="date" SortExpression="date" />

<asp:BoundField DataField="empolyeeno" HeaderText="empolyeeno"

SortExpression="empolyeeno" />

<asp:BoundField DataField="location" HeaderText="location"

SortExpression="location" />

<asp:BoundField DataField="position" HeaderText="position"

SortExpression="position" />

</Columns>

</asp:GridView>

.apx.cs code

Protected void bound(object sender, GridViewRowEventArgs e)

{

e.Row.Attributes.Add("onmouseover", "style.backgroundColor='#ffffff'");

e.Row.Attributes.Add("onmouseout", "style.backgroundColor='#C0C0C0'");

}