error using contentpublishingnotification cannot be used as type parameter - Using Umbraco and getting started

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Martin Rud 261 posts 1002 karma points c-trib

Nov 26, 2022 @ 05:46

Error using 'ContentPublishingNotification' ('cannot be used as type parameter...')

Hi forum,

I want a property value to be filled in and saved automatically if it's empty.

This works, but it triggers AFTER publish which is not what I need:

public void Handle(ContentPublishedNotification notification)
{
    foreach (var node in notification.PublishedEntities)
    {
        if (node.HasProperty("hashValue"))
        {
            var hashValue = node.GetValue<string>("hashValue");
            if (hashValue == null)
            {
                node.SetValue("hashValue", RandomString(6));
            }
        }
    }
}

Full code can be seen here: https://goonlinetools.com/snapshot/code/#iejbo6av3cdcw77czwmimq

This (ContentPublishedNotification changed to ContentPublishingNotification) is what I need, but it gives the error:

public void Handle(ContentPublishingNotification notification)
{
    foreach (var node in notification.PublishedEntities)
    {
        if (node.HasProperty("hashValue"))
        {
            var hashValue = node.GetValue<string>("hashValue");
            if (hashValue == null)
            {
                node.SetValue("hashValue", RandomString(6));
            }
        }
    }
}

Full error is:

cannot be used as type parameter 'TNotificationHandler' in the generic type or method 'UmbracoBuilderExtensions.AddNotificationHandler<TNotification, TNotif 
icationHandler>(IUmbracoBuilder)'. There is no implicit reference conversion from 'MrContentService.DontShout' to 'Umbraco.Cms.Core.Events.INotificationHand 
ler<Umbraco.Cms.Core.Notifications.ContentPublishedNotification>'. [C:\Users\marti\OneDrive - Martin Rud\Dev2.0\wallscreen_umbracoHeadless\wal 
lscreen_umbracoHeadless.csproj]

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Bo Jacobsen 606 posts 2404 karma points

Nov 26, 2022 @ 15:51

Hi Martin.

It seems the error is thrown where you add the notification handler.

Maybe you forgot to change from ContentPublishedNotification to ContentPublishingNotification?

So either:

public class DontShout : INotificationHandler<ContentPublishedNotification>
to 
public class DontShout : INotificationHandler<ContentPublishingNotification>

builder.AddNotificationHandler<ContentPublishedNotification, DontShout>();
to
builder.AddNotificationHandler<ContentPublishingNotification, DontShout>();

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Martin Rud 261 posts 1002 karma points c-trib

Nov 26, 2022 @ 20:47

Cool, thanks. You were right; I haven't updated the Startup.cs correctly:

It was

public void ConfigureServices(IServiceCollection services)
        {
            services.AddUmbraco(_env, _config)
                .AddBackOffice()
                .AddWebsite()
                .AddComposers()
                .AddNotificationHandler<ContentPublishedNotification, AddHashValue>()
                .Build();
        }

But should be:

public void ConfigureServices(IServiceCollection services)
        {
            services.AddUmbraco(_env, _config)
                .AddBackOffice()
                .AddWebsite()
                .AddComposers()
                .AddNotificationHandler<ContentPublishingNotification, AddHashValue>()
                .Build();
        }

(have also changed "DontShout" to "AddHashValue"), but that's only for making more sense. :)

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