How to implement WiX installer upgrade?

In the newest versions (from the 3.5.1315.0 beta), you can use the MajorUpgrade element instead of using your own.

For example, we use this code to do automatic upgrades. It prevents downgrades, giving a localised error message, and also prevents upgrading an already existing identical version (i.e. only lower versions are upgraded):

<MajorUpgrade
    AllowDowngrades="no" DowngradeErrorMessage="!(loc.NewerVersionInstalled)"
    AllowSameVersionUpgrades="no"
    />

Finally I found a solution - I'm posting it here for other people who might have the same problem (all 5 of you):

• Change the product ID to *

• Under product add The following:

  <Property Id="PREVIOUSVERSIONSINSTALLED" Secure="yes" />
  <Upgrade Id="YOUR_GUID">  
     <UpgradeVersion
        Minimum="1.0.0.0" Maximum="99.0.0.0"
        Property="PREVIOUSVERSIONSINSTALLED"
        IncludeMinimum="yes" IncludeMaximum="no" />
  </Upgrade> 
  

• Under InstallExecuteSequence add:

  <RemoveExistingProducts Before="InstallInitialize" /> 
  

From now on whenever I install the product it removed previous installed versions.

Note: replace upgrade Id with your own GUID