C#: Check if a site and web feature is enabled?

Question

I have created a custom MasterPage and added a feature event receiver to deploy it to my farm to be able to enable it using PowerShell.

I have followed this excellent blog post on how to create the feature in Visual Studio and everything work's perfect.

How to deploy a custom MasterPage in SharePoint 2013 using Visual Studio

However, when i tried to enable the feature in my test environment to a Site where publishing infrastructure already were published, i received this error several times on the application servers logs.

Event log message was: 'Failed to create the 'Images' library.'. Exception was: 'Microsoft.SharePoint.SPException: The feature failed to activate because a list at 'PublishingImages' already exists in this site. Delete or rename the list and try activating the feature again. at Microsoft.SharePoint.Publishing.Internal.ProvisioningHelper.AddList(SPListCollection lists, String urlName, String title, String description, Guid featureId, Guid[] previousVersionFeatureIds, Int32 templateType, Boolean& newListCreated) at Microsoft.SharePoint.Publishing.Internal.ProvisioningHelper.AddList(SPListCollection lists, String urlName, String title, String description, Guid featureId, Guid[] previousVersionFeatureIds, PublishingTemplateType templateType, Boolean& newListCreated) at Microsoft.SharePoint.Publishing.Internal.AreaProvisioner.CreateImagesLibrary(SPList approvalTaskList)'

It's kinda obvious that there were some problems as the publishing feature were already enabled and the "Images" (publishingimages) library were already in place. I would like to avoid this error when i'm ready to deploy the solution in our production environment.

From the blog post i mentioned earlier, this is a piece of the code for the event receiver:

string webAppRelativePath = topLevelSite.ServerRelativeUrl;
if (!webAppRelativePath.EndsWith("/"))
{
    webAppRelativePath += "/";
}

// Activate publishing infrastructure
site.Features.Add(new Guid("f6924d36-2fa8-4f0b-b16d-06b7250180fa"), true);

// Enumerate through each site and apply branding.
foreach (SPWeb web in site.AllWebs)
{
    // Activate the publishing feature for all webs.
    web.Features.Add(new Guid("94c94ca6-b32f-4da9-a9e3-1f3d343d7ecb"), true);
    web.MasterUrl = webAppRelativePath + "_catalogs/masterpage/MyCustom.master";
    web.CustomMasterUrl = webAppRelativePath + "_catalogs/masterpage/MyCustom.master";

    web.Update();
}

It's missing to check if the Publishing Infrastructure feature already are enabled. My server-side coding skills are kind of rusty, but i'm thinking to check if the site feature is added and then check for each web if the feature is enabled.

Am i on the right track code-wise?

Guid siteguid= new Guid("f6924d36-2fa8-4f0b-b16d-06b7250180fa");
Guid webguid = new Guid("94c94ca6-b32f-4da9-a9e3-1f3d343d7ecb");

// Check if the Publishing infrastructure feature is enabled
if ((site.Features[siteguid] == null)) {
    // Activate publishing infrastructure
    site.Features.Add(new Guid("f6924d36-2fa8-4f0b-b16d-06b7250180fa"), true);
}
    // Enumerate through each site and apply branding.
    foreach (SPWeb web in site.AllWebs)
    {
        // Check if the Publishing feature is enabled
        if (web.Features[webguid] == null){
        // Activate the publishing feature for all webs.
            web.Features.Add(new Guid("94c94ca6-b32f-4da9-a9e3-1f3d343d7ecb"), true);
        }

        web.MasterUrl = webAppRelativePath + "_catalogs/masterpage/MyCustom.master";
        web.CustomMasterUrl = webAppRelativePath + "_catalogs/masterpage/MyCustom.master";

        web.Update();
    }

Answer 1

Yes that is correct, site.Features[siteguid] this will return null if the feature is not already activated on the site.

So if (site.Features[siteguid] == null) will work as expected.

However the variable names should be fixed, siteguid doesn't seem to be Site GUID, it seems to be publishingFeatureGuid. Also webguid doesn't seem to be Web GUID, it seems to be masterPageFeatureGuid.