[gdal-dev] Ogr Problem with ReleaseResultSet

[Felix Obermaier]

Hello everyone,

I'm using OGR via its csharp bindings and accessing a MapInfo Table (TAB) using OGR's DataSource.ExecuteSQL function. 
The call is somewhat like.

_ogrLayer = _ogrDatasource.ExecuteSQL(
    @"SELECT CAST(OGR_STYLE AS character(255) AS LABEL " +
     "FROM LAYER WHERE OGR_STYLE LIKE 'LABEL%'", null, String.Empty)

_ogrLayer is a class scope variable, and remains assigned throughout the livecycle of the class.

I know that I'm supposed to release this layer calling _ogrDatasource.ReleaseResultSet(_ogrLayer);
but if I do so in the finalizer or an IDisposable.Dispose() function, I -sometimes- get an exception:

System.ApplicationException wurde nicht behandelt.
  Message=Pointer 'hDS' is NULL in 'OGR_DS_ReleaseResultSet'.

  Source=ogr_csharp
  StackTrace:
       bei OSGeo.OGR.DataSource.ReleaseResultSet(Layer layer)
       bei SharpMap.Data.Providers.Ogr.ReleaseOgrLayer()
       bei SharpMap.Data.Providers.Ogr.Dispose(Boolean disposing)
       bei SharpMap.Data.Providers.Ogr.Dispose()
       bei SharpMap.Data.Providers.Ogr.Finalize()
  InnerException:

Am I allowed to call _ogrLayer.SetSpatialPredicate(...) on a layer created with ExecuteSQL(...)?

Thanks in advance
Felix Obermaier

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