Programmatically Inherit Master Page and CSS in MOSS 2007

So recently I have been working on two small MOSS features:

• Change the master page and stylesheet settings for a site
• Staple the first feature to all site templates, so it is activated upon site creation

SharePoint Object Model:

• SPSite is a Site Collection
• SPWeb is a Site within a Site Collection

there are a couple of properties of the SPWeb object which we will be using:

• [web_object].MasterUrl
• [web_object].CustomMasterUrl
• [web_object].AlternateCssUrl

These values are read/write, so you can set the values to your own strings and the values in the database will be changed accordingly.

Note: all of the following is done within the FeatureActivated function of a custom class inheriting from the SPFeatureReceiver class. Now let’s dive into some code (these are all different methods I tried to no avail)

Created some variables and hard coded the locations within the feature:

string MasterUrl = "/_layouts/custom.master";
string CustomMasterUrl = "/_layouts/custom.master";
string AlternateCssUrl = "/StyleLibrary/Custom/CSS/stylesheet.css";
SPWeb web = (SPWeb)properties.Feature.Parent;
try {
web.MasterUrl = MasterUrl;
web.CustomMasterUrl = CustomMasterUrl;
web.AlternateCssUrl = AlternateCssUrl;
web.Update();
}catch { }

Set the values of the current site to the values from the root site:

SPWeb web = (SPWeb)properties.Feature.Parent;
try {
web.MasterUrl = web.Site.RootWeb.MasterUrl;
web.CustomMasterUrl = web.Site.RootWeb.CustomMasterUrl;
web.AlternateCssUrl = web.Site.RootWeb.AlternateCssUrl;
web.Update();
}catch { }

Set the values of the current site to the values from it’s parent site:

SPWeb web = (SPWeb)properties.Feature.Parent;
try {
web.MasterUrl = web.ParentWeb.MasterUrl;
web.CustomMasterUrl = web.ParentWeb.CustomMasterUrl;
web.AlternateCssUrl = web.ParentWeb.AlternateCssUrl;
web.Update();
}catch { }

None of these methods, upon going to the “Site Master Page Settings” page within a browser, showed the little radio button next to “Inherit site master page from parent of this site” as being checked. They did correctly set the master page and stylesheet links, but if I went to a parent site and changed the master page, the master page did not get changed on the site *unless* the “inherit” radio button was selected.

I decided to take this to the Content Database for the portal in which I was working. Looking in the dbo.Webs table, I found that if the “Inherit” radio button is selected, there are still values in the DB for AlternateCssUrl, MasterUrl, and CustomMasterUrl. Running the above code, would put the same values in these fields, but the “Inherit” radio button would not be selected. I then performed the following steps:

• Copy a row (one site) from the database to a text file
• Change each of the 3 settings (Site Master, System Master, and Alternate CSS) from “Inherit” to “Specify a …”
• Copy the same row from the database to the second row of the text file
• Change each of the 3 settings back to “Inherit”
• Copy the same row from the database to the third row of the text file
• Change each of the 3 settings back to “Specify a …”
• Copy the same row from the database to the fourth row of the text file

I then moved the side-scroll-bar all the way to the right (to confirm something in each lines was different) and they did not end at the same character, so I went to the beginning and compared vertically until I found different characters. There were a total of 3 instances of different characters (all 3 instances had the same characters) all within the same field, ‘MetaInfo’. These values were:

• “Inherit”: 547275
• “Specify a …”: 46616C73

Going back to the SharePoint Object Model, I discovered that there are two member properties to the SPWeb object which seem to correlate to site properties: Properties and AllProperties. I then tossed together a quick console app to output all Key/Value pairings for these two collections, and this is what came out:

• SPWeb.Properties (C# type SPPropertyBag)
  
  • vti_extenderversion: 12.0.0.4518
  • vti_associatevisitorgroup: 4
  • vti_defaultlanguage: en-us
  • vti_associategroups: 5;4;3;6;7;8;9;10;11;14;15;17;18;28
  • vti_associateownergroup: 3
  • vti_associatemembergroup: 5
• SPWeb.AllProperties (C# type Hashtable)
  • vti_extenderversion: 12.0.0.4518
  • __InheritsCustomMasterUrl: False
  • vti_associatevisitorgroup: 4
  • vti_categories: Business Competition Expense\ Report Goals/Objectives Ideas In\ Process
  • Miscellaneous Planning Schedule Travel VIP Waiting
  • vti_associatemembergroup: 5
  • vti_defaultlanguage: en-us
  • vti_associateownergroup: 3
  • vti_associategroups: 5;4;3;6;7;8;9;10;11;14;15;17;18;28
  • __InheritsAlternateCssUrl: False
  • vti_approvallevels: Approved Rejected Pending\ Review
  • __InheritsMasterUrl: False

Fancy that, there are three properties which interest me most at this point (indicated in red).
I simply set these values to “True” (note, that is a string of “True” and not a 1 or C# true)

However, it did not pull the correct values to begin with. Therefore, it would appear that SharePoint uses these settings for when the parent’s master pages/css are changed, and not relying on these settings for everytime the site is accessed.

All in all, here is the final code I came up with for my Feature (inside FeatureActivated function):

SPWeb web = (SPWeb)properties.Feature.Parent;
Hashtable hash = web.AllProperties;
try {
web.MasterUrl = web.ParentWeb.MasterUrl;
hash["__InheritsMasterUrl"] = “True”;
web.Update();
}catch { }
try {
web.CustomMasterUrl = web.ParentWeb.CustomMasterUrl;
hash["__InheritsCustomMasterUrl"] = “True”;
web.Update();}catch { }
try {
web.AlternateCssUrl = web.ParentWeb.AlternateCssUrl;
hash["__InheritsAlternateCssUrl"] = “True”;
web.Update();
}catch { }