public class FeatureClassDefinition : TableDefinition, System.IDisposable  

public async Task ObtainingDefinitionFromGeodatabase()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
    {
        using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file\\sdefile.sde"))))
        {
            // Remember that for Enterprise databases you have to qualify your dataset names with the DatabaseName and UserName.
            TableDefinition enterpriseTableDefinition = geodatabase.GetDefinition<TableDefinition>("LocalGovernment.GDB.CitizenContactInfo");

            // It does not matter if the dataset is within a FeatureDataset or not.
            FeatureClassDefinition featureClassDefinition = geodatabase.GetDefinition<FeatureClassDefinition>("LocalGovernment.GDB.FireStation");

            // GetDefinition For a RelationshipClass.
            RelationshipClassDefinition relationshipClassDefinition = geodatabase.GetDefinition<RelationshipClassDefinition>("LocalGovernment.GDB.AddressPointHasSiteAddresses");

            // GetDefinition For a FeatureDataset.
            FeatureDatasetDefinition featureDatasetDefinition = geodatabase.GetDefinition<FeatureDatasetDefinition>("LocalGovernment.GDB.Address");
        }
    });
}

public async Task ObtainingDefinitionsFromGeodatabase()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
    {
        using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file\\sdefile.sde"))))
        {
            IReadOnlyList<FeatureClassDefinition> enterpriseDefinitions = geodatabase.GetDefinitions<FeatureClassDefinition>();
            IEnumerable<Definition> featureClassesHavingGlobalID = enterpriseDefinitions.Where(definition => definition.HasGlobalID());

            IReadOnlyList<FeatureDatasetDefinition> featureDatasetDefinitions = geodatabase.GetDefinitions<FeatureDatasetDefinition>();
            bool electionRelatedFeatureDatasets = featureDatasetDefinitions.Any(definition => definition.GetName().Contains("Election"));

            IReadOnlyList<AttributedRelationshipClassDefinition> attributedRelationshipClassDefinitions = geodatabase.GetDefinitions<AttributedRelationshipClassDefinition>();

            IReadOnlyList<RelationshipClassDefinition> relationshipClassDefinitions = geodatabase.GetDefinitions<RelationshipClassDefinition>();
        }
    });
}

public async Task ObtainingRelatedDefinitionsFromGeodatabase()
{
    await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
    {
        using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file\\sdefile.sde"))))
        {
            // Remember the qualification of DatabaseName. for the RelationshipClass.

            RelationshipClassDefinition enterpriseDefinition = geodatabase.GetDefinition<RelationshipClassDefinition>("LocalGovernment.GDB.AddressPointHasSiteAddresses");
            IReadOnlyList<Definition> enterpriseDefinitions = geodatabase.GetRelatedDefinitions(enterpriseDefinition, DefinitionRelationshipType.DatasetsRelatedThrough);
            FeatureClassDefinition enterpriseAddressPointDefinition = enterpriseDefinitions.First(defn => defn.GetName().Equals("LocalGovernment.GDB.AddressPoint"))
        as FeatureClassDefinition;

            FeatureDatasetDefinition featureDatasetDefinition = geodatabase.GetDefinition<FeatureDatasetDefinition>("LocalGovernment.GDB.Address");
            IReadOnlyList<Definition> datasetsInAddressDataset = geodatabase.GetRelatedDefinitions(featureDatasetDefinition, DefinitionRelationshipType.DatasetInFeatureDataset);
            FeatureClassDefinition addressPointInAddressDataset = datasetsInAddressDataset.First(defn => defn.GetName().Equals("LocalGovernment.GDB.AddressPoint"))
        as FeatureClassDefinition;

            RelationshipClassDefinition addressPointHasSiteAddressInAddressDataset = datasetsInAddressDataset.First(defn => defn.GetName().Equals("LocalGovernment.GDB.AddressPointHasSiteAddresses"))
        as RelationshipClassDefinition;
        }
    });
}

public RowCursor SortWorldCities(FeatureClass worldCitiesTable)
{
    using (FeatureClassDefinition featureClassDefinition = worldCitiesTable.GetDefinition())
    {
        Field countryField = featureClassDefinition.GetFields()
          .First(x => x.Name.Equals("COUNTRY_NAME"));
        Field cityNameField = featureClassDefinition.GetFields()
          .First(x => x.Name.Equals("CITY_NAME"));

        // Create SortDescription for Country field
        SortDescription countrySortDescription = new SortDescription(countryField);
        countrySortDescription.CaseSensitivity = CaseSensitivity.Insensitive;
        countrySortDescription.SortOrder = SortOrder.Ascending;

        // Create SortDescription for City field
        SortDescription citySortDescription = new SortDescription(cityNameField);
        citySortDescription.CaseSensitivity = CaseSensitivity.Insensitive;
        citySortDescription.SortOrder = SortOrder.Ascending;

        // Create our TableSortDescription
        TableSortDescription tableSortDescription = new TableSortDescription(
          new List<SortDescription>() { countrySortDescription, citySortDescription });

        return worldCitiesTable.Sort(tableSortDescription);
    }
}