Wix 4.0 Error WIX0200 The Package element contains an unhandled extension element 'WixUI'

[ijuedt]

• Im using latest Visual Studio 2019 (16.11.35), have installed HeatWave extension (V1.0.4), also tried fresh re-install after last VS update.
• Project file shows Sdk="WixToolset.Sdk/4.0.2"
• Installed extensions are WixToolset.Netfx.wixext, WixToolset.UI.wixext, and WixToolset.Util.wixext in version 5.0.0.
• My xmlns includes are
  • xmlns:ui="http://wixtoolset.org/schemas/v4/wxs/ui"
  • xmlns:NetFX="http://wixtoolset.org/schemas/v4/wxs/netfx"
  • xmlns:util="http://wixtoolset.org/schemas/v4/wxs/util"
• wxs file has been converted from wix 3.
• My UI Element is <ui:WixUI Id="WixUI_FeatureTree" />

Might this be a version mismatch between wix 4 and wix 5?

[ijuedt]

Found out myself: there were additional errors unrelated to wix toolset which were kind of hiding the real problem, while my UI-related error hid those other errors. After temporarily excluding my UI element and removing the errors, the real error was revealed: my extensions did "not have support for WiX Toolset v4.0.2". Then I only had to change the version declaration to "5.0.0".

[robmen]

I think we're leaving issues open so they are easier for others to find.