private ThemeUnique GetThemeUnique()
{
    //获得工作空间连接信息
    WorkspaceConnectionInfo connectionInfo = new WorkspaceConnectionInfo(@"D:\SampleData\world\World.sxwu");
    //实例化工作空间
    Workspace workspace = new Workspace();
    ThemeUnique theme = null;
    try
    {
        //打开已有的工作空间并打开指定名称的地图
        workspace.Open(connectionInfo);
        Map map = new Map(workspace);
        map.Open("世界地图");

        //获取当前地图所包含的图层集合对象
        Layer layer = map.Layers["World@world#1"];

        //获取专题图层的单值专题图对象
        theme = layer.Theme as ThemeUnique;
    }
    finally
    {
        //释放资源
        workspace.Dispose();
    }
    //返回新的单值专题图对象
    return new ThemeUnique(theme);
}