How can I display a message in a master page with ViewData?

Question

How can I display a message on the master page. The message is sent by the action.

public ActionResult DisplayMessage()
{
    ViewData["hello"] = "Hello!";
    return View();
}

Answer 1

In your view, do the following:

<%= html.encode(ViewData("Hello")) %>

If you want to place this data in another area outside of your view within your master page, you will need to define a new content placeholder.

Master Page:

<div id="somewhereOtherThanYourNormalViewArea">
    <asp:ContentPlaceHolder ID="SecondaryContent" runat="server" />
</div>

View:

<asp:Content ID="Content2" ContentPlaceHolderID="SecondaryContent" runat="server">
    <%= html.encode(ViewData("Hello")) %>
</asp:Content>

Answer 2

This is actually pretty simple. Just add the following in your controller:

ViewData["PassedToMaster"] = "From content page!";

Then in your MasterPage you can just add the following code to look for it and if it is there do something with it:

<% if (ViewData["PassedToMaster"] != null)
   { %>
   <%= ViewData["PassedToMaster"].ToString() %>
<% } %>