Have you ever encountered this error:

Invalid postback or callback argument.  Event validation is enabled using <pages enableEventValidation=”true”/> in configuration or <%@ Page EnableEventValidation=”true” %> in a page.  For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them.  If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation.

That’s pretty long error message. I get this exception if I add items to drop-down control from JavaScript. The question is how to use ClientScriptManager.RegisterForEventValidation method?

First, let’s reproduce the problem. Create a new website and copy/paste this code:

<asp:DropDownList ID="dd" runat="server">
  <asp:ListItem>One</asp:ListItem>
  <asp:ListItem>Two</asp:ListItem>
</asp:DropDownList>
<asp:Button ID="Button1" runat="server" Text="Test" />

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"
  type="text/javascript"></script>
<script type="text/javascript">
  $(function()
  {
    $("#<%= dd.ClientID %>").append($("<option />")
      .val(3)
      .text("Three!"));
  });
</script>

If you select option “Three” sure enough, exception is thrown. To prevent it you need to supply all possible values for drop-down control:

protected override void Render(HtmlTextWriter writer)
{
  Page.ClientScript.RegisterForEventValidation(dd.UniqueID, "3");
  Page.ClientScript.RegisterForEventValidation(dd.UniqueID, "4");
  Page.ClientScript.RegisterForEventValidation(dd.UniqueID, "11");
  // and so on
  base.Render(writer);
}

The exception is fixed but server variable for drop-down control is useless – it has no idea that you’ve added new item so dd.SelectedValue will give One, not 3. You need to read POST variable directly instead, like this:

protected void Page_Load(object sender, EventArgs e)
{
   if (IsPostBack)
      Response.Write(Request.Form[dd.UniqueID]);
}

Here’s how you can view whitespaces in Emacs:

M-x whitespace-mode RET

By default, Emacs uses bright colours to highlight whitespaces that are in wrong place (in Emacs’ opinion):

To disable colouring add the following to your .emacs file:

; disable colours in whitespace-mode
(setq whitespace-style '(space-mark tab-mark))

Now it’s much better:

I assign showing white spaces to Ctrl+Shift+8 to mimick Visual Studio behaviour:

(global-set-key (kbd "C-*") 'whitespace-mode)

When I work with WiX source code I need to create lots of GUIDs. In my Visual Studio 2005 editor all I need to do is to press Alt+G and new GUID magically appears at the cursor. Achieving this is very easy:

1. Open Macros IDE by selecting Tools | Macros | Macros IDE.
2. Create new macro:

Public Sub InsertGuid()

DTE.ActiveDocument.Selection.Text = Guid.NewGuid().ToString()

End Sub

3. Bind new macro to Alt+G keyboard shortcut. Open Options dialog, select Environment, then Keyboard on the left. Type “InsertGuid” to locate the macro you just created. Assign Alt+G to it.
   
   Fortunately, no standard command is assigned to Alt+G by default.

1. Locate Resources for Visual Basic.tlb in C:\Documents and Settings\All Users\Application Data\Adobe\InDesign\Version 5.0\Scripting Support\5.0 folder.

2. Open command prompt and execute:

TlbImp.exe "Resources for Visual Basic.tlb" /out:Interop.InDesign.dll

TlbImp.exe is located in C:\Program Files\Microsoft Visual Studio 8\SDK\v2.0\Bin folder on my machine. This will generate Interop.InDesign.dll file. This is an interop assembly.

3. Add reference to Interop.InDesign.dll to your project.

4. Use this code:

using System;
using InDesign;

namespace HelloInDesign
{
   class Program
   {
      static void Main(string[] args)
      {
         object missing = Type.Missing;
         Type type = Type.GetTypeFromProgID("InDesign.Application.CS3");
         if (type == null)
         {
            throw new Exception("Adobe InDesign CS3 is not installed");
         }
         _Application app = (_Application)Activator.CreateInstance(type);
         Document document = (Document)app.Documents.Add(true, missing);
         Page page = (Page)document.Pages[1];
         TextFrame textFrame = page.TextFrames.Add(missing,
            idLocationOptions.idUnknown, missing);
         textFrame.GeometricBounds = new string[] { "6p", "6p", "24p", "24p" };
         textFrame.Contents = "Hello from .Net!";
      }
   }
}

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