SF_10.1, SF_10.2, SF_11.0, SF_11.1, SF_11.2, SF_12.0, SF_12.1, SF_12.2, SF_13.0, SF_13.1, SF_13.2, SF_13.3, SF_14.0, SF_14.1, SF_14.2, SF_14.3 - https://docs.sitefinity.com/for-developers-query-blog-posts

QueryAllBlogPostsNativeAPI.cs

using System.Collections.Generic;
using System.Linq;
using Telerik.Sitefinity.Blogs.Model;
using Telerik.Sitefinity.GenericContent.Model;
using Telerik.Sitefinity.Modules.Blogs;

namespace SitefinityWebApp
{
    public class QueryAllBlogPostsNativeAPI
    {
        private List<BlogPost> GetAllBlogPostsNativeAPI()
        {
            BlogsManager blogsManager = BlogsManager.GetManager();

            return blogsManager.GetBlogPosts().Where(b => b.Status == ContentLifecycleStatus.Live && b.Visible).ToList();
        }
    }
}