Wix: Can't set a property with a custom action

Question

I have a dialog that's part of my installer to enter a activation key. I'm able to pass the value from this control,

         <Control Id="KEY1" Type="Edit" Property="KEY1" Height="17" Width="45" X="50" Y="150" Text="{5}" Indirect="no"/>

to my custom action,

 session["KEY1"]

But I can't seem to figure out why I can't set session["KEY1"] = "test" and see the value in my control... I tried everything but nothing works. Here's my current code,

C# (Custom Action)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Deployment.WindowsInstaller;

namespace Test.CustomActions
{
    public class CustomActions
    {
        [CustomAction]
        public static ActionResult TestAction(Session session)
        {
            session.Log("Begin CustomAction1");

            session["KEY1"] = "lol";
            string[] lines = { session["KEY1"], "Second line", "Third line" };
            System.IO.File.WriteAllLines(@"C:\CustomAction.txt", lines);

            return ActionResult.Success;
        }
    }
}

Wix

<?xml version="1.0" encoding="UTF-8"?>
<Wix xmlns="http://schemas.microsoft.com/wix/2006/wi">
  <Fragment>
    <Property Id="KEY1" Value="Test" Secure="yes"/>
    <Property Id="Key2"/>
    <Property Id="Key3"/>
    <Property Id="Key4"/>
    <Property Id="Key5"/>
    <Property Id="Key6"/>
    <UI>
      <Dialog Id="ActivationCodeDlg" Width="370" Height="270" Title="!(loc.InstallDirDlg_Title)">
        <Control Id="BannerBitmap" Type="Bitmap" X="0" Y="0" Width="370" Height="44" TabSkip="no" Text="!(loc.InstallDirDlgBannerBitmap)"/>
        <Control Id="Title" Type="Text" X="15" Y="6" Width="200" Height="15" Transparent="yes" NoPrefix="yes" Text="{\WixUI_Font_Title}Activation Code"/>
        <Control Id="Description" Type="Text" X="25" Y="23" Width="280" Height="15" Transparent="yes" NoPrefix="yes" Text="Please enter your activation code"/>
        <Control Id="BannerLine" Type="Line" X="0" Y="44" Width="370" Height="0"/>

        <Control Id="KEY1" Type="Edit" Property="KEY1" Height="17" Width="45" X="50" Y="150" Text="{5}" Indirect="no"/>
        <Control Id="Hyphen1" Type="Text" Height="17" Width="5" X="96" Y="153" Text="-"/>
        <Control Id="Key2" Type="Edit" Property="Key2" Height="17" Width="45" X="100" Y="150" Text="{5}"/>
        <Control Id="Hyphen2" Type="Text" Height="17" Width="5" X="146" Y="153" Text="-"/>
        <Control Id="Key3" Type="Edit" Property="Key3" Height="17" Width="45" X="150" Y="150" Text="{5}"/>
        <Control Id="Hyphen3" Type="Text" Height="17" Width="5" X="196" Y="153" Text="-"/>
        <Control Id="Key4" Type="Edit" Property="Key4" Height="17" Width="45" X="200" Y="150" Text="{5}"/>
        <Control Id="Hyphen4" Type="Text" Height="17" Width="5" X="246" Y="153" Text="-"/>
        <Control Id="Key5" Type="Edit" Property="Key5" Height="17" Width="45" X="250" Y="150" Text="{5}"/>
        <Control Id="Hyphen5" Type="Text" Height="17" Width="5" X="296" Y="153" Text="-"/>
        <Control Id="Key6" Type="Edit" Property="Key6" Height="17" Width="15" X="300" Y="150" Text="{1}"/>

        <Control Id="Activate" Type="PushButton" X="50" Y="200" Width="56" Height="17" Text="Activate">
          <Publish Event="DoAction" Value="Testing"/>
        </Control>

        <Control Id="BottomLine" Type="Line" X="0" Y="234" Width="370" Height="0"/>
        <Control Id="Next" Type="PushButton" X="236" Y="243" Width="56" Height="17" Default="yes" Text="!(loc.WixUINext)"/>
        <Control Id="Back" Type="PushButton" X="180" Y="243" Width="56" Height="17" Text="!(loc.WixUIBack)"/>
        <Control Id="Cancel" Type="PushButton" X="304" Y="243" Width="56" Height="17" Cancel="yes" Text="!(loc.WixUICancel)">
          <Publish Event="SpawnDialog" Value="CancelDlg">1</Publish>
        </Control>
      </Dialog>
    </UI>
    <CustomAction Id='Testing' BinaryKey='FooBinary' DllEntry='TestAction' Execute='immediate'/>
    <Binary Id='FooBinary' SourceFile='Feenics.Keep.CustomActions.CA.dll'/>
  </Fragment>
</Wix>

Answer 1

Where is your code for InstallExecuteSequence/InstallUISequence?

<InstallUISequence>
    <Custom Action="Testing" Sequence="1" />
</InstallUISequence>

Maybe adding this will make this custom action happen before your UI dialogs are called.

Edit: Also, have you done any detailed debugging (verbose logging) of your installer to check what is happening and when things are running? After you have your .MSI output, open a command prompt and do:

    msiexec.exe /i <yourmsi> /l*vx Output.txt

This will give you detailed output of your stuff!