Identify Image Service

A client has requested the ability to identify elevation values from a DEM.  The DEM has been published as an image service but there does not appear to be a way that we could find using geocortex to identify the image service.  Are we missing something or is there not an "out of the box" way to identify an Image Service?  Since we couldn't figure out how to do this, I thought I would try to create a workflow to do this even though it seems like overkill.  This seems very straightforward and easy but I am having some trouble. 

The basic steps to my workflow:

1. draw a point (capture geometry) -> returns a ArcGIS.Client.Geometry.Geometry Object
2. convert the output geometry object to ArcGIS.Client.Geometry.MapPoint object (Get Centroid)
3. Use Web Request to get pixel value at point.  This is where I am running into an issue.  The "Parameters" argument allows for a dictionary where you can pass in the arguements for the request against the REST Service.  I do not know how to properly pass in the MapPoint object for the "geometry" argument needed for the identify method of the Image Service.  This is what the point object looks like when I print it out as a string:

Point[X=499463.408069459, Y=4968147.78447395, WKID=26915]

I think I need to convert it to JSON as a string inside the Parameters diciontary.  I tried this as the dictionary and am getting an error (where point is my MapPoint object):

New System.Collections.Generic.Dictionary(Of String, String) From { { "geometry", point.ToString() }, { "geometryType", "esriGeometryPoint" }, {"f", "json"}, {"token", Token} }

The next piece will be getting the "value" from the JSON response from the identify method's JSON return.  I need to get to that pont first though.  Any help would be appreciated!