Returning Any Struct From a Templated Function

I have an array of bytes. I built a code generator that will take these array of bytes (which are messages sent from an exchange) into managed structs via the following ReinterpretCast implementation:

        public static T ReinterpretCast<T>(byte[] message) where T : struct
        {
            GCHandle handle = GCHandle.Alloc(message, GCHandleType.Pinned);
            T theStruct = (T)Marshal.PtrToStructure(handle.AddrOfPinnedObject(), typeof(T));
            handle.Free();
            return theStruct;

        }

For example ExecutionReportCancel534 item = ReinterpretCast<ExecutionReportCancel534>(myByteArray);

As you can see, the last three digits of this type is 534. 534 is the ID that corresponds to this type. My code generator creates a dictionary that maps these IDs to types. For instance,

        public const Dictionary<int, Type> intToStructMap = new Dictionary<int, Type>()
        {
                { 500, Negotiate500 },
                { 501, NegotiationResponse501 },
                { 502, NegotiationReject502 },
                { 503, Establish503 },
                { 504, EstablishmentAck504 },
                { 505, EstablishmentReject505 },
        };

Now, what I want to do is write a function that takes: 1) an array of bytes, and 2) an integer, and return a type that is reinterpreted from this array of bytes. For example, while I know this is not possible, I'd like this function to operate like this:

        public static intToStructMap[templateId] ReinterpretCast(byte[] message, int templateId)
        {
            Type typeOfInterest = intToStructMap[templateId];
            var returnedStruct = ReinterpretCast<typeOfInterest>(message);
            return returnedStruct;
        }

In other words, I want to return any of the types in my dictionary (intToStructMap) given the templateId that corresponds to this type.

Whats the best way to do so?