topic Re: Unable to cast COM object of type 'System.__ComObject' (to IStandAloneTable) in ArcObjects SDK Questions

Unable to cast COM object of type 'System.__ComObject' (to IStandAloneTable)

PieterLinks — Wed, 30 Jun 2010 08:58:50 GMT

Hi,

When I try to add a table from a MDB to a MapControl's StandAloneTableCollection, I get an error. What am I doing wrong? The table exists and is not empty.

{System.InvalidCastException: Unable to cast COM object of type 'System.__ComObject' to interface type 'ESRI.ArcGIS.Carto.IStandaloneTable'.
This operation failed because the QueryInterface call on the COM component for the interface with IID '{FFC6B179-E3EC-11D3-A096-00C04F6BC626}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).
   at <snip>.AddTableToMapControl() in <snip><snip>}

public void AddTableToMapControl()
{
IMapControl3 pMapControl = (IMapControl3)this.AxMapControl1.Object;
IWorkspaceFactory accessWorkspaceFactory = new AccessWorkspaceFactoryClass();
IFeatureWorkspace featureWorkspace;
      ITable geodatabaseTable;
      IStandaloneTable geodatabaseStTable;
      IStandaloneTableCollection pStTableCollection = pMapControl as IStandaloneTableCollection;

      try
      {
            featureWorkspace = accessWorkspaceFactory.OpenFromFile("c:/somewhere/somedb.mdb", 0) as IFeatureWorkspace;
            geodatabaseTable = featureWorkspace.OpenTable("SomeTable");
            geodatabaseStTable = (IStandaloneTable)geodatabaseTable; <----- here it fails with the error
            pStTableCollection.AddStandaloneTable(geodatabaseStTable);
}
catch (Exception ex)
{
    MessageBox.Show(ex.ToString());
}
}

Many thanks,

Re: Unable to cast COM object of type 'System.__ComObject' (to IStandAloneTable)

NeilClemmons — Wed, 30 Jun 2010 11:36:57 GMT

The Table coclass does not implement IStandAloneTable, which is why you're getting the error. To add a standalone table to the map, you have to create a new one and set its Table property. It's basically the same thing you do when you want to add a feature layer - create a new feature layer and set its FeatureClass property.

Re: Unable to cast COM object of type 'System.__ComObject' (to IStandAloneTable)

PieterLinks — Wed, 30 Jun 2010 13:27:33 GMT

Thanks Neil for your answer.

I did as you wrote: created a new StandAloneTable, set its Table property to geodatabaseTable and tried to add it to the collection, but there it fails.

Never mind, I made a class which contains the ITable and a Name property, and put that in an ICollection - an ITableCollection doesn't have a Name property.