[mapguide-users] SelectFeatures using SetFilter gives null exception

[Jackie Ng]

I see nothing indicating what feature class you are querying from. The fact
that you are calling SelectFeatures() from the MgLayer instead of the
MgFeatureService means that you need to new the MgMap object with the
MgSiteConnection as indicated here:
http://trac.osgeo.org/mapguide/wiki/MapGuideRfc9

- Jackie


Tony wrote:
> 
> Hi 
> i am using the following code to find the   Pipes that are greater than
> 12'  i am getting null exeception 
> the sample code in dev guide is the same. why i am getting error
> anyone
> 
> thanks
> tony
> 
> MgUserInformation userInfo = new MgUserInformation(mgSessionId);
>             MgSiteConnection siteConnection = new MgSiteConnection();
>             siteConnection.Open(userInfo);
> 
>             MgResourceService resourceService =
> siteConnection.CreateService(MgServiceType.ResourceService) as
> MgResourceService;
>             MgFeatureService featureService =
> siteConnection.CreateService(MgServiceType.FeatureService) as
> MgFeatureService;
>             
>             MgFeatureQueryOptions districtQuery = new
> MgFeatureQueryOptions();
>             districtQuery.SetFilter("Size > 12");
>             
>             MgMap map = new MgMap();
>             map.Open(resourceService, "General Public Map");
>             MgLayer layer = map.GetLayers().GetItem("SD") as MgLayer;
>            
>             MgFeatureReader featureReader =
> layer.SelectFeatures(districtQuery);
> //getting error here 
>             featureReader.ReadNext();
>             
>             MgByteReader districtGeometryData =
> featureReader.GetGeometry("Geometry");
>             MgAgfReaderWriter agfReaderWriter = new MgAgfReaderWriter();
>             MgGeometry districtGeometry =
> agfReaderWriter.Read(districtGeometryData);
> 

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