Pass and Use variables in ASP.net server to the client HTML or JavaScript code - Multiple ways

Any public variables available during the page load (page_load event) is usable as variables in the HTML code. Below are the multiple ways of using them.

Using ASP.net variables:

public partial class VariableTest : System.Web.UI.Page
{
    public string url = "http://www.google.com";
    protected void Page_Load(object sender, EventArgs e)
    {
       
    }
}

HTML Usage:

<a href="<%= url %>">click here</a>

Using Sessions:

These session variables might have loaded at any stage of your application. Even global.asax loading will do. Just make sure that they are available during page load.

protected void Page_Load(object sender, EventArgs e)
    {
        Session["newurl"] = "http://www.google.com";
    }

HTML Usage:

<a href="<%= Session["newURL"] %>">Click here</a>

Using Web.Config:
    Web.config file has the variable value as mentioned below.

<appSettings>
    <add key="newURL" value="http://www.google.com"/>
</appSettings>

HTML Usage:

<a href="<%= ConfigurationManager.AppSettings["newURL"] %>">Click Here</a>

Make sure that the namepsaces are referenced from your page. Otherwise you will have to change like System.Configuration.ConfigurationManager.AppSettings["newURL"]

Using the Variables in JavaScript
     Basically, all the above mentioned usages work like a string replace. So, you can even use it in javascript codes as shown below.

<a href="#" onclick="javascript:alert('<%= urls %>');return false;">Click here</a>

Using these variables in Server controls.
     Controls with server rendering enabled (runat="server") will not work using the methods mentioned above. Use Page.DataBind() to do the trick for you. Make sure that you are using <%# %> in this case

Server Code:

public partial class VariableTest : System.Web.UI.Page
{
    public string newurl = "http://www.google.com";
    protected void Page_Load(object sender, EventArgs e)
    {
        Page.DataBind();
    }
}

Designer Code:

<asp:HyperLink ID="HyperLink1" runat="server" NavigateUrl="<%# newurl %>">HyperLink</asp:HyperLink>

OR

<asp:HyperLink ID="HyperLink1" runat="server" NavigateUrl="<%# this.newurl %>">HyperLink</asp:HyperLink>