public IReadOnlyList<T> GetDefinitions<T>()
where T: Definition

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"))))
    {
      var enterpriseDefinitions = 
        geodatabase.GetDefinitions<FeatureClassDefinition>();
      IEnumerable<Definition> featureClassesHavingGlobalID = 
        enterpriseDefinitions.Where(definition => definition.HasGlobalID());

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

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

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

public async Task GetFeatureClassesInRelationshipClassAsync()
{
  await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
  {
    using (Geodatabase geodatabase = new Geodatabase(new FileGeodatabaseConnectionPath(new Uri(@"C:\Data\LocalGovernment.gdb"))))
    {
      IReadOnlyList<RelationshipClassDefinition> relationshipClassDefinitions = 
        geodatabase.GetDefinitions<RelationshipClassDefinition>();

      foreach (var relationshipClassDefinition in relationshipClassDefinitions)
      {
        IReadOnlyList<Definition> definitions = 
          geodatabase.GetRelatedDefinitions(relationshipClassDefinition,
            DefinitionRelationshipType.DatasetsRelatedThrough);

        foreach (var definition in definitions)
        {
          System.Diagnostics.Debug.WriteLine(
            $"Feature class in the RelationshipClass is:{definition.GetName()}");
        }
      }
    }
  });
}