Default.aspx

<asp:Label ID="lblnumara" runat="server" Visible="false" />

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" CellPadding="4"

                ForeColor="#333333" GridLines="None">

                <FooterStyle BackColor="#990000" Font-Bold="True" ForeColor="White" />

                <RowStyle BackColor="#FFFBD6" ForeColor="#333333" />

                <Columns>

                    <asp:TemplateField HeaderText="Butoncuk">

                        <ItemTemplate>

                            <asp:Button Text="Tıkla" ID="btnLink" runat="server" OnClick="ShowDetay" />

                        </ItemTemplate>

                    </asp:TemplateField>

                    <asp:TemplateField>

                    <ItemTemplate><%#Eval("mahkeme")%></ItemTemplate>

                    </asp:TemplateField>

                </Columns>

                <PagerStyle BackColor="#FFCC66" ForeColor="#333333" HorizontalAlign="Center" />

                <SelectedRowStyle BackColor="#FFCC66" Font-Bold="True" ForeColor="Navy" />

                <HeaderStyle BackColor="#990000" Font-Bold="True" ForeColor="White" />

                <AlternatingRowStyle BackColor="White" />

            </asp:GridView>

Default.aspx.cs

protected void Page_Load(object sender, EventArgs e)

    {

        using (OleDbConnection conn = new OleDbConnection(ConfigurationManager.AppSettings["conn"]))

        {

            OleDbDataAdapter adp = new OleDbDataAdapter("", conn);

            adp.SelectCommand.CommandText = "SELECT  dosyaID, mahkeme FROM tbl_dava_dosya";

            DataTable dt = new DataTable();

            adp.Fill(dt);

            GridView1.DataKeyNames = new string[] { "dosyaID" };

            GridView1.DataSource = dt;

            GridView1.DataBind();

        }

    }

    public void ShowDetay(object sender, EventArgs e)

    {

        Button btnEdit = sender as Button;

        btnEdit.PostBackUrl="Detay.aspx";

        GridViewRow row = (GridViewRow)btnEdit.NamingContainer;

        int bildirimId=Convert.ToInt32(this.GridView1.DataKeys[row.DataItemIndex].Value);

        lblnumara.Text=bildirimId.ToString();

        Server.Transfer("Detay.aspx",true);

    }

--------------------------------------------------

Detay.aspx.cs

protected void Page_Load(object sender, EventArgs e)

    {

        if (PreviousPage!=null)

        {

            Response.Write((this.PreviousPage.FindControl("lblnumara") as Label).Text);

        }

    }