The HiddenField control provides you with a way to store information in the page without displaying it. This control enables a developer to store a non-displayed value. You can use the Hidden Field control to store state values. Note that because the value of a Hidden Field is rendered to the client browser, it is not suitable for storing security-sensitive values.

 <asp:HiddenField ID="HiddenField1" runat="server" />
 <asp:HiddenField ID="HiddenField1" runat="server" /> 
 <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox> 
 <asp:Label ID="Label1" runat="server"></asp:Label> 
 <asp:Button ID="Button1" runat="server" OnClick="Button1_Click"     Text="Button" /> 
 
protected void Page_Load(object sender, EventArgs e) 
    { 
        HiddenField1.Value = TextBox1.Text; 
       
    } 
    
    protected void Button1_Click(object sender, EventArgs e) 
    { 
        Label1.Text = HiddenField1.Value; 
    }