public FileSystemDatastore( 
   FileSystemConnectionPath connectionPath
)

public async Task OpenShapefileFeatureClass()
{
  await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
  {
    FileSystemConnectionPath fileConnection = new FileSystemConnectionPath(new Uri("path\\to\\folder\\containing\\shapefiles"), FileSystemDatastoreType.Shapefile);
    using (FileSystemDatastore shapefile = new FileSystemDatastore(fileConnection))
    {
      FeatureClass taxLotsFeatureClass = shapefile.OpenDataset<FeatureClass>("TaxLots");
      FeatureClass manHolesFeatureClass = shapefile.OpenDataset<FeatureClass>("ManHoles.shp"); // Can use the .shp extension, but its not needed.
      Table taxDetailsTableWithoutExtension = shapefile.OpenDataset<Table>("TaxDetails");
      Table taxDetailsTable = shapefile.OpenDataset<Table>("TaxDetails.dbf");
    }
  });
}

public async Task OpenCADFeatureClass()
{
  await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
  {
    FileSystemConnectionPath fileConnection = new FileSystemConnectionPath(new Uri("path\\to\\folder\\containing\\CAD"), FileSystemDatastoreType.Cad);
    using (FileSystemDatastore cadDatastore = new FileSystemDatastore(fileConnection))
    {
      // note - extension is required
      FeatureClass cadDataset = cadDatastore.OpenDataset<FeatureClass>("hatchplayboundaries.dwg");
      // take note of the pattern for referencing a feature class. 
      FeatureClass cadfeatureClass = cadDatastore.OpenDataset<FeatureClass>("hatchplayboundaries.dwg:Polyline");

      int numRows = 0;
      using (RowCursor cursor = cadfeatureClass.Search())
      {
        while (cursor.MoveNext())
          numRows++;
      }
    }
  });
}

// Create a FileSystemConnectionPath using the folder path.
FileSystemConnectionPath connectionPath = new FileSystemConnectionPath(new System.Uri(@"C:\Temp"), FileSystemDatastoreType.Raster);
// Create a new FileSystemDatastore using the FileSystemConnectionPath.
FileSystemDatastore dataStore = new FileSystemDatastore(connectionPath);
// Open the raster dataset.
RasterDataset fileRasterDataset = dataStore.OpenDataset<RasterDataset>("Sample.tif");