public enum FileSystemDatastoreType : System.Enum, System.IComparable, System.IConvertible, System.IFormattable, System.ISpanFormattable  

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");