Proper way to check if a Factory Code is Projected or Geographic

Question

I would like to create a SpatialReference with ArcObjects, but I won't know whether it is Projected or Geographic, I'll only have the SRID. Is it fine practice to use 'ISpatialReferenceFactory.CreateGeographicCoordinateSystem' with a 'try', see if it fails, and if so, use 'CreateProjectedCoordinateSystem', and if that fails, give a message that it won't work? I have a feeling that I shouldn't use Exceptions in this way, but I'm not aware of an alternative.

I am aware of these answers, but they don't quite answer the question:

Arcobjects: Is my spatial reference Geographic or Projected?

How to programmatically determine whether a spatial reference factory code is valid?

Edit: This is after the fact, but I have become aware of this answer

Answer 1

Further to what Vince has indicated.. create a spatial reference with ISpatialReferenceFactory3 (CreateSpatialReference is the easiest) and then find out what it is. You have the SRID/EPSG code so create a spatial reference object and then test its type (ISpatialReference is implemented by both geographic and projected coordinate systems and also unknown coordinate systems but hopefully you won't encounter one of them).

ISpatialReferenceFactory3 pSRfact = new SpatialReferenceEnvironmentClass();
ISpatialReference pSR = pSRfact.CreateSpatialReference(Code);
if (pSR is IProjectedCoordinateSystem)
{ 
    // do your projected stuff
}
else if (pSR is IGeographicCoordinateSystem)
{
    // do your geographic stuff
}

Or if you don't like is use the as operator (returns null if the type can't be cast)

ISpatialReferenceFactory3 pSRfact = new SpatialReferenceEnvironmentClass();
ISpatialReference pSR = pSRfact.CreateSpatialReference(Code);
IProjectedCoordinateSystem pProjSR = pSR as IProjectedCoordinateSystem;
IGeographicCoordinateSystem pGeoSR = pSR as IGeographicCoordinateSystem;
if (pProjSR != null)
{ 
    // do your projected stuff
}
else if (pGeoSR != null)
{
    // do your geographic stuff
}

of course if the code isn't supported neither will be created, make sure there's a way in your code to avoid junk SRID/EPSG codes safely.

Answer 2

So this seems to be the correct way to check if a WKID is Projected or Geographic...

edit: This is what I had done, but @Michael Miles Stimson found the proper method to use instead of relying on try/catch.

public ISpatialReference getSpatialReference_byCode(int srid)
        {
            ISpatialReference spatialReference;
            ISpatialReferenceFactory sr_factory = new SpatialReferenceEnvironmentClass();
            try
            {
                spatialReference = sr_factory.CreateGeographicCoordinateSystem(srid);
            }
            catch
            {
                try
                {
                    spatialReference = sr_factory.CreateProjectedCoordinateSystem(srid);
                }
                catch
                {
                    throw new NotImplementedException("This is an unkown Spatial Reference");
                }
            }

            return spatialReference;
        }