how to get selected row cell value at gridview row databound

For this, you should include a click event for the "Link button", In that click event you should take the "Client ID" and store it in the session, then redirect to the next page, where you can get this session value.

protected void lnkOpenClient_Click(object sender, EventArgs e)
{
GridViewRow grdrow = (GridViewRow)((LinkButton)sender).NamingContainer;
// Hope that you are storing the client id in any of the cell get it from there
string clientID = grdrow.Cells[0].Text;
// Store the client id in your session
Session["ClientID"] = clientID;
// Finally open the new url
Response.Redirect("Yourtargetpage.aspx");
}

For more information, follow the below url:

http://www.dotnetbull.com/2013/05/how-to-handle-click-event-of-linkbutton.html

Hope this helps!