A couple things wrong:
-First, the example uses "Storemode.replace", yet the description says: Store a value using the specified key, whether the key already exists or not. Will overwrite a value if the given key/value already exists. (that's not what replace does)
-Second, according to the layout of the docs, "replace" should be an update operation, not a store operation. However, it is a "storemode" so there may need to be some cross referencing?
-Third, the parent page (http://www.couchbase.com/docs/couchbase-sdk-net-1.1/api-reference-set.html) lists the ExecuteStore methods out of order compared to how they are shown on the child page