When you want to reset your current theme that has been applied to your SharePoint site in code, you may try code like:
but that won’t work because there is no "default" theme.
After looking in the SPTHEMES.XML file found in the C:Program FilesCommon FilesMicrosoft SharedWeb Server Extensions14TEMPLATELAYOUTS1033 folder, you do see there is a theme with a theme name of "none". That makes sense so you try:
But often that still won’t work. Frustrating. Keep searching and after a review of Microsoft’s documentation on the SPWeb.ApplyTheme method, you see it.
Use this method only when the UI is in backward compatibility mode (SPWeb.UIVersion = 3).
Not too many of us use UIVersion = 3 in SharePoint 2010, so what do you do now?
Easy. Use the replacement class, ThmxTheme (found in Microsoft.SharePoint.Utilities), in particular the ThmxTheme.RemoveThemeFromWeb method.
Where site is the SPWeb and the bool value states if you wish to also remove the theme’s styles. Setting this to true will remove the theme specific styles that was created when the theme was applied to the web, but I have found that setting this to true can cause issues because of security concerns. I suggest you try settings the bool value to true if you wish to have this method remove theme styles files, but if you receive errors, set this to false and it will likely work. This is not the best for housekeeping, but may make your life easier.
As a quick example, say in a feature receiver when you deactivate a feature, the following code would remove the theme from an entire site collection if the feature is scoped to the site level.
public override void FeatureDeactivating(SPFeatureReceiverProperties properties)
//go and get the root site collection
SPSite siteCollection = properties.Feature.Parent as SPSite;
if (siteCollection != null)
SPWeb topLevelSite = siteCollection.RootWeb;
foreach (SPWeb site in siteCollection.AllWebs)
//reset the theme in case one was applied