Could not load file or assembly 'Tridion.ContentDelivery.WebControls'

We did a upgrade from Tridion 5.3 to Tridion 2011 SP1. On upgraded Content Delivery Server we copied our existing website folder (From Existing Tridion 5.3). When we try to hit Login.aspx page we got a error "The type or namespace name 'Broker' does not exist in the namespace 'Tridion.ContentDelivery'. To resolve this we have changed the import from 'Tridion.ContentDelivery.Broker' to 'Tridion.ContentDelivery.Meta', this resolved the issue. Now we are getting new error message "Could not load file or assembly 'Tridion.ContentDelivery.WebControls' or one of its dependencies". What can be done to resolve this issue.

Solution

Some .NET CD API classes moved namespaces in Tridion 2009, and there is now only one single core Content Delivery .NET DLL: Tridion.ContentDelivery.dll.

This means when upgrading you need to refactor your web application code (as you are doing with Tridion.ContentDelivery.Meta) and configuration accordingly. Most likely this error is coming from the web controls registered in web.config. Look for where the CD web controls are registered, this should for 2009+ read:

<controls>
    <add tagPrefix="tridion" namespace="Tridion.ContentDelivery.Web.UI"
           assembly="Tridion.ContentDelivery" />
</controls>