CODEWITHSUNDEEP
linqentity-frameworklinq-to-entities
GibboK
GibboK

Reputation: 73998

EF - cannot convert from System.Linq.IQueryable to System.Data.Objects.ObjectQuery

I need subtract the result of contentCategories from allCategories at the moment I use .Except method but I receive an error.

Any idea what I'm doing wrong... many thanks

Error   2   Argument 1: cannot convert from 'System.Linq.IQueryable<System.Data.Objects.DataClasses.EntityCollection<WebProject.DataAccess.DatabaseModels.CmsCategory>>' to 'System.Data.Objects.ObjectQuery<WebProject.DataAccess.DatabaseModels.CmsCategory>'

            int contentId = Int32.Parse(uxContentsListSelector.SelectedValue);
            var allCategories = from category in context.CmsCategories select category;
            var contentCategories = from content in context.CmsContents
                                          where content.ContentId == contentId
                                          select content.CmsCategories;
            var result = context.CmsCategories.Except(contentCategories);

Upvotes: 3

Views: 5436

Answers (2)

Aducci
Aducci

Reputation: 26694

You need to add an additional from in clause in order to get a flattened list.

var contentCategories = from content in context.CmsContents
                        from cat in content.CmsCategories
                        where content.ContentId == contentId
                        select cat;

I would then change your Except method to an Any method

var result = context.CmsCategories.Where(cat => !contentCategories.Any(c => c.CategoryId == cat.CategoryId));

Upvotes: 3

Matteo Mosca
Matteo Mosca

Reputation: 7458

That's because of the last select you're doing. Also you're code is highly reduntant. Let's take it by steps:

var allCategories = from category in context.CmsCategories select category;

You can rewrite the same in a more concise way:

var allCategories = context.CmsCategories;

Then this is wrong: you're selectin a query of collections instead of a single collection:

var contentCategories = from content in context.CmsContents
                                      where content.ContentId == contentId
                                      select content.CmsCategories;

The correct way to do that is:

var contentCategories = (from content in context.CmsContents
                                      where content.ContentId == contentId
                                      select content).First().CmsCategories;

Which is, again, redundant, and can be written in a better way:

var contentCategories = context.CmsContents.First(c => c.ContentId == contentId).CmsCategories;

The last statement is right.

Upvotes: 2

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