gridview paging takes two clicks instead of one click

<asp:GridView ID="gridName" runat="server" BackColor="White" OnPageIndexChanging="gridName_PageIndexChanging"
            BorderColor="#336666" AllowPaging="True" CssClass="Grid" 
            HorizontalAlign="Center" EnableViewState="true" Font-Size="Medium" ShowFooter="True" OnRowEditing="gridName_RowEditing" >
            
            <footerstyle forecolor="#333333" />
            <HeaderStyle ForeColor="White" Font-Size="Medium" HorizontalAlign="Center" />
            <pagerstyle backcolor="#336666" forecolor="White" horizontalalign="Center" />
            <rowstyle forecolor="#333333" horizontalalign="Center" verticalalign="Middle" />            
            <SelectedRowStyle Font-Bold="True" />

protected void gridName_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        gridName.PageIndex = e.NewPageIndex;

        if (!IsPostBack && !IsCallback)
        {
            gridName.DataBind();
        }
    }
    
    protected void gridName_RowEditing(object sender, GridViewEditEventArgs e)
    {
        gridName.EditIndex = e.NewEditIndex;
        
        
    }