如何在ASPX页面中访问变量？

Question

ASPX:

<form id="form1" runat="server">
    <%
       int a = 25;
    %>
    <asp:Label ID="Label1" runat="server" 
         Text='<%#a %>'></asp:Label>
</form>

Code behind:

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
       DataBind();
    }
}

Error:

The name 'a' does not exist in the current context

Answer 1

Found solution:

ASPX:

<form id="form1" runat="server">
    <asp:Label ID="Label1" runat="server" 
         Text="<%#a %>"></asp:Label>
</form>

Code behind:

public int a;
protected void Page_Load(object sender, EventArgs e)
{
   if (!IsPostBack)
   {
      a = 25;
      DataBind();
   }
}

Answer 2

This way will work.. ASPX:

<form id="form1" runat="server">
         <asp:Label ID="Label1" runat="server"></asp:Label>
</form>

code behind:

public int a;
protected void Page_Load(object sender, EventArgs e)
{
   if (!IsPostBack)
   {
      a = 25;
    Label1.Text=a.ToString();
   }
}

Answer 3

something to note, is that the aspx file is compiled to a class by the the System.Web.UI.Page class which implements IHttpHandler, the created class inherit the aspx.cs/aspx.vb, which explain the inherits in the <%@ Page %> directive, and by logic, you cannot reference a variable declared in aspx code nugget in code behind.
As a work around, you can declare protected members in code behind and access those from code nuggets.