Asp.Net Mvc Linq issue

Question

I know my problem is really basic. If I write /api/category/1, I wanna list all Tales with the categoryId==1. I wrote this code, but it gives an error.

[HttpGet]
public IEnumerable<Tale> GetAllTalesByCategory(int id)
{
    var tales = TaleService.FindAllTale().Select(x => new Tale
    {
        TaleId = x.TaleId,
        TaleName = x.TaleName,
        Content = x.Content,
        VoicePath = x.VoicePath
    }).Where(x => new Tale
    {
        x.Categories.Select(c => c.CategoryId).First() == id                    
    });
}

Error:

Error   1   Cannot initialize type 'MasalYuvasi.Entities.Tale' with a collection initializer because it does not implement 'System.Collections.IEnumerable' D:\MvcProject\MasalYuvasi\MasalYuvasi\Controllers\DenemeController.cs   33  13  MasalYuvasi

Models:

public class Tale
{
    public int TaleId { get; set; }
    public string TaleName { get; set; }
    public string Content { get; set; }
    public string VoicePath { get; set; }
    public virtual ICollection<Category> Categories { get; set; }
    public Tale()
    {
        this.Categories = new List<Category>();
    }   
}

public class Category
{
    public int CategoryId { get; set; }
    public string CategoryName { get; set; }
    public virtual ICollection<Tale> Tales { get; set; }
    public Category()
    {
        this.Tales = new List<Tale>();
    }
}

See "Collection Initializers"

JDB
– JDB

2013-12-12 18:21:57 +00:00
Commented Dec 12, 2013 at 18:21 — JDB
– JDB, Commented Dec 12, 2013 at 18:21
What does your FindAllTale() return?

ataravati
– ataravati

2013-12-12 18:29:19 +00:00
Commented Dec 12, 2013 at 18:29 — ataravati
– ataravati, Commented Dec 12, 2013 at 18:29
IEnumerable<Tale> is return.

BerdaN
– BerdaN

2013-12-12 18:36:27 +00:00
Commented Dec 12, 2013 at 18:36 — BerdaN
– BerdaN, Commented Dec 12, 2013 at 18:36

ataravati · Accepted Answer · 2013-12-12 18:27:23Z

2

Try this:

[HttpGet]
public IEnumerable<Tale> GetAllTalesByCategory(int id)
{
    var tales = TaleService.FindAllTale().Select(x => new Tale
    {
        TaleId = x.TaleId,
        TaleName = x.TaleName,
        Content = x.Content,
        VoicePath = x.VoicePath
    }).Where(x => x.Categories.Select(c => c.CategoryId).First() == id).ToList();
}

Fixed the where condition, and added .ToList().

edited Dec 12, 2013 at 18:27

ataravati

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answered Dec 12, 2013 at 18:22

pjobs

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2 Comments

JDB Over a year ago

You should add that ToList() will change the behavior of the program by causing the query to execute immediately rather than the deferred execution of the Where clause object (which is still an IEnumerable<Tale>).

BerdaN Over a year ago

I take this error "An exception of type 'System.InvalidOperationException' occurred in System.Core.dll but was not handled in user code"

Community · Accepted Answer · 2017-05-23 11:57:34Z

1

The problem is that your code is using a collection initializer here:

new Tale
{
    x.Categories.Select(c => c.CategoryId).First() == id                    
}

I'm not sure what this code is supposed to be doing, but as x.Categories.Select(c => c.CategoryId).First() == id will return a bool, I don't think this is doing what you want it to.

Based on your comment:

I want to list in the category of tales. Forexample I have 2 tales in CategoryId is 1. If I write "/api/category/1" ı want to list this 2 tales.

I think you are looking for something simpler than what you've got. You want to select Tales (represented by x) where Any of the categories have a CategoryId of id:

.Where(x => x.Categories.Any(c => c.CategoryId == id ));

Note that you can append .ToList() to the end of the where clause, as suggested by pjobs, but this may have a subtle effect on the behavior of your application. For more detail, see LINQ and Deferred Execution.

edited May 23, 2017 at 11:57

CommunityBot

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answered Dec 12, 2013 at 18:23

JDB

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8 Comments

BerdaN Over a year ago

I want to list in the category of tales. Forexample I have 2 tales in CategoryId is 1. If I write "/api/category/1" ı want to list this 2 tales.

BerdaN Over a year ago

Thanks for answer. Now I didn't take any error but return just like that "[]" Can u check pls my table image postimg.org/image/bb7t90vqr and if I need to say I create TalesCategory table with modelBuilder.

JDB Over a year ago

@BerdaN - I do not have access to that website (blocked by corporate filter) and your original question has been (apparently) answered. If you have a new question, please create a new post.

JDB Over a year ago

@BerdaN - Keep in mind that you should spend some time researching the question yourself before posting it. Stack Overflow is not a debugging service and many users will take issue with a cascade of questions, one bug after another, without any evidence that you've attempted to solve the issue yourself.

BerdaN Over a year ago

I think ı didnt explain. I said return just it "[]" but I expect return like "[{"TaleId":2,"TaleName":"dasd","Content":"saddasdaaaaaa","VoicePath":"asdasdas"] data.

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