How to get a PostTeaser URL or Guid in another document in Api?

This syntax should work: Documents.WithAllData["/Blogs/TotalTech-Blog/December-2018/Second-blog-post"].GetValue("BlogPostTeaser")

However I'm not sure it is a good approach to insert macro in a custom layout.

Unfortunately, it also works in the console, but not in a custom layout. How do I get a Blog Post Teaser in a custom layout knowing the Blog alias patch? Maybe not a macro

You can write c# code within layout, just wrap it with <script runat="server">...</script> and you are good to go.

The only question I have is why would you need to do it within layout? Won't it be easier to use some viewer?

I use a custom layout to prepare a custom web part. I need this for a reason.

It could be easily macro permission thing. Take a look at this topic

Or you can do it directly in the code, not need for macro. Just use attachment API. The code below is not fully tested it just to give you the direction:)

(https://docs.kentico.com/api11/content-management/attachments)

<script runat="server">
protected void Page_PreRender(object sender, EventArgs e)
{
    CMS.DocumentEngine.TreeProvider tree = new CMS.DocumentEngine.TreeProvider(CMS.Membership.MembershipContext.AuthenticatedUser);

    // Gets a page
    CMS.DocumentEngine.TreeNode page = tree.SelectNodes()
        .Path("/News/%")
        .OnCurrentSite()
        .Culture("en-us")
        .FirstObject;


  string attachmentGUID = "";
    if (page != null)
    {
        foreach (CMS.DocumentEngine.DocumentAttachment attachment in page.AllAttachments)
        {
            if (someCondition) {
                attachmentGUID =  attachment.AttachmentGUID.ToString();
                break;
            }
        }
    }  

  test.Text = attachmentGUID ;
}
</script>
<asp:Literal runat="server" ID="test" Text="test" />

At the end I used

var pages = CMS.DocumentEngine.DocumentHelper.GetDocuments("CMS.BlogPost") .OnCurrentSite() .Path("/Blogs/Blog/%") .WhereEquals("NodeAliasPath", pageAlias) .Published();

if (pages != null) { foreach (var blogpage in pages) { Guid guid = blogpage.GetGuidValue("BlogPostTeaser", Guid.Empty); img = CMS.DocumentEngine.AttachmentURLProvider.GetAttachmentUrl(guid, ""); }

}

Thanks