public T OpenDataset<T>( 
   string name
)
where T: Dataset

public async Task OpeningDatasetsFromGeodatabase()
{
  await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
  {
    using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file\\sdefile.sde"))))
    {
      using (Table table = geodatabase.OpenDataset<Table>("LocalGovernment.GDB.EmployeeInfo"))
      {
      }

      // Open a featureClass (within a feature dataset or outside a feature dataset).
      using (FeatureClass featureClass = geodatabase.OpenDataset<FeatureClass>("LocalGovernment.GDB.AddressPoint"))
      {
      }

      // You can open a FeatureClass as a Table which will give you a Table Reference.
      using (Table featureClassAsTable = geodatabase.OpenDataset<Table>("LocalGovernment.GDB.AddressPoint"))
      {
        // But it is really a FeatureClass object.
        FeatureClass featureClassOpenedAsTable = featureClassAsTable as FeatureClass;
      }

      // Open a FeatureDataset.
      using (FeatureDataset featureDataset = geodatabase.OpenDataset<FeatureDataset>("LocalGovernment.GDB.Address"))
      {
      }

      // Open a RelationsipClass.  Just as you can open a FeatureClass as a Table, you can also open an AttributedRelationshipClass as a RelationshipClass.
      using (RelationshipClass relationshipClass = geodatabase.OpenDataset<RelationshipClass>("LocalGovernment.GDB.AddressPointHasSiteAddresses"))
      {
      }
    }
  });
}

// Create a FileGeodatabaseConnectionPath using the path to the gdb. Note: This can be a path to a .sde file.
FileGeodatabaseConnectionPath geodatabaseConnectionPath = new FileGeodatabaseConnectionPath(new Uri(@"C:\Temp\rasters.gdb"));
// Create a new Geodatabase object using the FileGeodatabaseConnectionPath.
Geodatabase geodatabase = new Geodatabase(geodatabaseConnectionPath);
// Open the raster dataset.
RasterDataset gdbRasterDataset = geodatabase.OpenDataset<RasterDataset>("sample");