This is one of those “..note to self” blogs to document for future reference the meaning of the exception message:

Format of the initialization string does not conform to specification starting at index 0

To me this actually means:

When the provider is being initialized with a collection of key/value pairs, the string that defines those key/value pairs is not properly formatted.

Perhaps that would be obvious to most but in my case, the exception would be difficult to track down in the field since a provider to my provider was actually throwing the exception.  In particular, my provider (AspNetSqlMembershipProvider) had a properly configured ConnectionStringName attribute but the format of the corresponding connection string (in the web.config connectionstrings section) was not properly formatted as “data source=…”. (I had gone with the proverbial connectionString="Foo" to see if/how it would blow.) 

In fact, it was the SqlClient Data Provider that was originating the exception, at least in my case.

I post this here so that if I get “oldTimers” or if anyone else suffers from the exception, it may help offer a clue.

Brian Mishler