public virtual string GetMetadata()

{
    //Search for only layers/tables here if needed.
    MapMember mapMember = map.GetLayersAsFlattenedList().FirstOrDefault();
    if (mapMember == null) return;
    //Note: Run within a QueuedTask
    //Gets whether or not the MapMember stores its own metadata or uses metadata retrieved
    //from its source. This method must be called on the MCT. Use QueuedTask.Run
    bool doesUseSourceMetadata = mapMember.GetUseSourceMetadata();

    //Sets whether or not the MapMember will use its own metadata or the metadata from
    //its underlying source (if it has one). This method must be called on the MCT.
    //Use QueuedTask.Run
    mapMember.SetUseSourceMetadata(true);

    //Does the MapMember supports metadata
    var supportsMetadata = mapMember.SupportsMetadata;

    //Get MapMember metadata
    var metadatstring = mapMember.GetMetadata();
    //TODO:Make edits to metadata using the retrieved mapMetadata string.

    //Set the modified metadata back to the mapmember (layer, table..)
    if (mapMember.GetCanEditMetadata())
        mapMember.SetMetadata(metadatstring);
}