Unable to cast COM object of type 'System.__ComObject' to interface type 'ESRI.ArcGIS.Geodatabase.ISubtypes'

[marwamohamed]

I am trying to get the subtypes of a feature class that has subtypes but i get this error

"

Unable to cast COM object of type 'System.__ComObject' to interface type 'ESRI.ArcGIS.Geodatabase.ISubtypes'. This

operation failed because the QueryInterface call on the COM component for the interface with IID '{AEF78514-848F-11D2-

AABA-00C04FA37B82}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002

(E_NOINTERFACE))

"

at this line :ESRI.ArcGIS.Geodatabase.ISubtypes subtypes = (ESRI.ArcGIS.Geodatabase.ISubtypes)sourceFeatureClass;

Here is the code:

protected override List<String> GetDistinctGroupFieldValues(MigrationFeatureClassSource source)

        {

            if (source.SourceName == "Mekka")

            {

                try

                {

                    List<String> distinctValues = null;

                    ESRI.ArcGIS.Geodatabase.IFeatureClass sourceFeatureClass =

source.DataSource.GetFeatureWorkSpaceOfDataSource().OpenFeatureClass(source.SourceTableName);

                    ESRI.ArcGIS.Geodatabase.ISubtypes subtypes = (ESRI.ArcGIS.Geodatabase.ISubtypes)sourceFeatureClass;

                        ESRI.ArcGIS.Geodatabase.IEnumSubtype enumSubtype;

                        int subtypeCode;

                        string subtypeName;

                        if (subtypes.HasSubtype)

                        {

                            distinctValues = new List<String>();

                            enumSubtype = subtypes.Subtypes;

                            subtypeName = enumSubtype.Next(out subtypeCode);

                            while (subtypeName != null)

                            {

                                subtypeName = enumSubtype.Next(out subtypeCode);

                                if (subtypeName.Contains("???"))

                                {

                                    distinctValues.Add(subtypeCode.ToString());

                                }

                            }

                        }

                  return distinctValues ;

                }

                catch (Exception ex)

                {

                    Logger.LoggerInstance.LogError(ex.Message, DateTime.Now, "GetDistinctGroupFieldValues",

"MigrationFeatureClass", m_tableName);

                    throw new Exception(ex.Message);

                }

            }

            else

            {

              return base.GetDistinctGroupFieldValues(source);

            }

        }

[seria]

This exception will occur if the object returned by the following method is in fact not an IFeatureClass residing in a geodatabase:

IFeatureClass sourceFeatureClass = source.DataSource.GetFeatureWorkSpaceOfDataSource().OpenFeatureClass(source.SourceTableName);

I am thinking that your source.SourceTableName above is in fact just a normal excel CSV file (table) or a shapefile, and not really a table/feature class  coming from a real geodatabase. Remember, Subtypes can only be created on a feature class (or table) residing in a geodatabase. This means, it has got to be a feature class (or table) residing in (a) a Personal Geodatabase, (b) File Geodatabase, (c) ArcSDE Geodatabase (multiuser geodatabase). A shapefile would not work. An Excel CSV table would not work. The below line of code would fail (you cannot cast a shapefile or CSV excel table to an ISubtypes Object) because subtypes are only available within the geodatabase container.

ISubtypes subtypes = (ISubtypes)sourceFeatureClass;

Try replacing source feature class with a known feature class residing in  a file geodatabase or an ArcSDE geodatabase, and see if you still get the error.

Documentation on Subtypes can be found at the below URLs:

A Quick tour of Subtypes

http://resources.arcgis.com/en/help/main/10.2/index.html#/A_quick_tour_of_subtypes/005r0000000100000...

Creating Subtypes (using ArcCatalog)

http://resources.arcgis.com/en/help/main/10.2/index.html#/Creating_subtypes/005r00000003000000/

Creating Subtypes (using ArcObjects)

http://resources.arcgis.com/en/help/arcobjects-net/conceptualhelp/index.html#/d/0001000003r3000000.h...