Krdytkyu

Applying Sitecore Experience Commerce 9.0 Update-3 on top of a fresh Update-2 (on Sitecore 9.0.2) installation results in this exception, after performing step "6.5. Republish and rebuild the search indexes", in the upgrade guide:

[TypeLoadException: Could not load type 'Fields' from assembly
'Sitecore.XA.Foundation.Mvc, Version=3.7.0.0, Culture=neutral,
PublicKeyToken=null'.]

Sitecore.Commerce.XA.Foundation.Common.Providers.RenderingViewProvider.GetCustomViewPath(IRendering
rendering) +0

Sitecore.Commerce.XA.Foundation.Common.Providers.RenderingViewProvider.Resolve(ControllerContext
controllerContext, IRendering rendering, String viewName) +240

Sitecore.Commerce.XA.Foundation.SiteMetadata.Controllers.MetadataController.Index()
+34 lambda_method(Closure , ControllerBase , Object ) +90 System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext
controllerContext, IDictionary2 parameters) +229

System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext
controllerContext, ActionDescriptor actionDescriptor, IDictionary2
parameters) +35

System.Web.Mvc.<>c__DisplayClass15.b__12()
+80 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter
filter, ActionExecutingContext preContext, Func1 continuation) +454

System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter
filter, ActionExecutingContext preContext, Func1 continuation) +454

System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext
controllerContext, String actionName) +524

Inspecting all the related dlls with dotPeek, I see this:

protected virtual string GetCustomViewPath(IRendering rendering)
{
string str = (string) null;
Item settingsItem = this.MultisiteContext.GetSettingsItem(rendering.Item);
if (settingsItem != null)
str = settingsItem[Sitecore.XA.Foundation.Mvc.Templates.Settings.Fields.get_CustomRenderingViewPath()];
return str;
}

Settings doesn't seem to exist, and therefore Fields does not exist. I cannot find any property called "CustomRenderingViewPath" anywhere.

Any ideas?

This is because of a missed step. The documentation isn't very clear about it, but you must update to Sitecore Experience Accelerator 1.8 to get version 3.8.0.0 of the required dlls.