using System.Web.UI.HtmlControls;
 protected void Page_Load(object sender, EventArgs e)
  {
    for (int i = 0; i < 4; i++)
    {
      HtmlInputCheckBox htmlInputCheckBox = new HtmlInputCheckBox();//这里用CheckBox也是一样的
      htmlInputCheckBox.ID = "check" + i;
      Container.Controls.Add(htmlInputCheckBox);
    }
  }
  protected void Button1_Click(object sender, EventArgs e)
  {
    for (int i = 0; i < 4; i++)
    {
      Label1.Text += "<br/>" + (Container.FindControl("check" + i) as HtmlInputCheckBox).Checked.ToString();
    }
  }

<form id="form1" runat="server">
  <div id="Container" runat="server">
  </div>
  <asp:Button ID="Button1" runat="server" Text="Button" onclick="Button1_Click" />
  <asp:Label ID="Label1" runat="server"></asp:Label>
  </form>

 public string GetCheckBox()
  {
    return "<input name=\"Checkbox1\" type=\"checkbox\"/>";//这里必须设置name，Id没有用
  }
  protected void Button1_Click(object sender, EventArgs e)
  {
    if (Request.Form["Checkbox1"] == null)//如果Checkbox1为未选中状态Request.Form["Checkbox1"]值为null
    {
      Label1.Text += "<br/>Fasle";
    }
    else//如果Checkbox1为选中状态Request.Form["Checkbox1"]值为on
    {
      Label1.Text += "<br/>True";
    }
  }

<form id="form1" runat="server">
  <div>
    <%=GetCheckBox() %>
  </div>
  <asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />
  <asp:Label ID="Label1" runat="server"></asp:Label>
  </form>