Can't update Lambda expression in Umbraco upgrade

Question

I am in the process of updating Umbraco version. There is a blog, but the macro outputting blog posts is hiccuping. Originally, it was something like:

dynamic result = Model.Descendants().Where("NodeTypeAlias == \"BlogPost\"");
var values = new Dictionary<string,object>();
values.Add("currentDate", DateTime.Now) ;
result = result.Where("blogDate <= currentDate", values);

In v7.3, the debug error says

Error loading partial view macro (View: ~/Views/MacroPartials/Blog Post List.cshtml) 'object' does not contain a definition for 'Where'

I tried changing the Where cause to a different Lambda expression

Where(x => x.GetPropertyValue<DateTime>("blogDate") < values)

but then the error changes to

error CS1977: Cannot use a lambda expression as an argument to a dynamically dispatched operation without first casting it to a delegate or expression tree type

Any advice would be greatly appreciated. Thanks in advance!

score 0 · Answer 1 · answered Apr 07 '16 at 22:06

Are you sure there's data in Model? Maybe it's Model.Content? I also usually use DescendantsOrSelf(), maybe Descendants() isn't returning anything. The generic error message tells us nothing, so.maybe try breaking down your code a little, just to isolate the problem. What versions are you upgrading from?

score 0 · Answer 2 · answered Apr 08 '16 at 07:52

Try by using the typed version (so you also have intellisense):

DateTime now = DateTime.Now;
var posts = Model.Content.Descendants("BlogPost").Where(n => n.GetPropertyValue<DateTime>("blogDate") < now);

foreach (IPublishedContent post in posts)
{
    ...
}

score 0 · Answer 3 · answered Apr 08 '16 at 13:56

Have you tried going with UmbracoHelper?

If your page inherits Umbraco.Web.Mvc.UmbracoViewPage then you will be able to structure your query like this:

var result = Umbraco.AssignedContentItem.Descendants().Where(x => x.DocumentTypeAlias == "BlogPost");

Otherwise, instantiate the UmbracoHelper first and then use it to access node information:

var umbracoHelper = new UmbracoHelper(UmbracoContext.Current);
var result = umbracoHelper.AssignedContentItem.Descendants.Where(x => x.DocumentTypeAlias == "BlogPost");

If you don't have the assigned content (probably accessing data through AJAX) or current context, try hiding the node ID in HTML and transferring this info to your code.

Can't update Lambda expression in Umbraco upgrade

3 Answers3