How do I get the gridview checkboxfield value when I press a button?

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False">
    <Columns>
        <asp:BoundField DataField="Title" HeaderText="Title" />
        <asp:TemplateField>
            <ItemTemplate>
                <asp:CheckBox ID="chk" runat="server" Checked='<%#Eval("CheckValue") %>' />
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>
<asp:Button ID="btnGetCheck" runat="server" Text="Get Check" OnClick="btnGetCheck_Click" />

class CheckExample
{
    public string Title { get; set; }
    public bool CheckValue { get; set; }
}
protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        List<CheckExample> list = new List<CheckExample>();
        list.Add(new CheckExample() { Title = "A", CheckValue = false });
        list.Add(new CheckExample() { Title = "B", CheckValue = false });
        list.Add(new CheckExample() { Title = "C", CheckValue = false });
        list.Add(new CheckExample() { Title = "D", CheckValue = false });
        list.Add(new CheckExample() { Title = "E", CheckValue = false });

        GridView1.DataSource = list;
        GridView1.DataBind();
    }
}

protected void btnGetCheck_Click(object sender, EventArgs e)
{
    foreach (GridViewRow row in GridView1.Rows)
    {
        bool chkValue = ((CheckBox)row.FindControl("chk")).Checked;
    }
}