CODEWITHSUNDEEP
c#asp.netlinqasp.net-web-api
phroureo
phroureo

Reputation: 379

Using ==Null in Linq not working to find null values

I found this question that suggested I should be able to accomplish my goal. I want to return only posts where the parent_post field is null.

Here's how my data looks in my table that it's pulling from: 

create table dbo.post  
(post_id int not null primary key,
thread_id int not null,
parent_post int,
creator int not null,
post_text nvarchar(max) not null)

insert into dbo.post (post_id, thread_id, parent_post, creator, post_text) values
(1,1,null,123,'Here is the first post in the forum!'),
(2,1,null,123,'Here is the second post!'),
(3,1,2,123,'Here is a reply! Let''s hope it works!'),
(4,1,2,123,'Here is a second reply. I wonder how this looks?'),
(5,1,3,123,'Here is a third level deep reply. ')

In my controller for my API, it looks like this: 

    [HttpGet]
    [Route("api/threads/{thread_id}")]
    [AcceptVerbs("GET")]
    public IEnumerable<post> GetPostsByThread(long thread_id)
    {
        return db.post.Where(post => post.thread_id == thread_id && post.parent_post == null).ToList();
    }

(I got rid of the piece from the linked question that used "Trim" because my blanks are never going to be white space)

Now, I would expect that this would return the records for posts 1 and 2. However, when I call the API, it returns nothing. When I go to http://localhost:#####/api/threads/1 (or any other number), it returns this: 

<ArrayOfpost xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.datacontract.org/2004/07/Test_Forum.Models"/>

Edited to add the Model for Post

namespace Test_Forum.Models
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Data.Entity.Spatial;

    public partial class post
    {

        [Key]
        [Required]
        [Column(Order = 0)]
        public long post_id { get; set; }

        [Required]
        [Column(Order = 1)]
        public long thread_id { get; set; }

        [Required]
        [Column(Order = 2)]
        public long? parent_post { get; set; }

        [Required]
        [Column(Order = 3)]
        public long creator { get; set; }

        [Required]
        [Column(Order = 4)]
        public DateTime create_date { get; set; }

        [Required]
        [Column(Order = 5)]
        public DateTime update_date { get; set; }

        [Required]
        [Column(Order = 6)]
        public string post_text { get; set; }
    }
}

Upvotes: 0

Views: 101

Answers (1)

Gianluca Conte
Gianluca Conte

Reputation: 500

There is a simple mismatch between the post model class and the database table. I get back the data using the following model for post:

public post {
    [Key]
    [Required]
    [Column(Order = 0)]
    public long post_id { get; set; }

    [Required]
    [Column(Order = 1)]
    public long thread_id { get; set; }

    //[Required]
    [Column(Order = 2)]
    public long? parent_post { get; set; }

    [Required]
    [Column(Order = 3)]
    public long creator { get; set; }

    //[Required]
    [Column(Order = 4)]
    public DateTime? create_date { get; set; }

    //[Required]
    [Column(Order = 5)]
    public DateTime? update_date { get; set; }

    //[Required]
    [Column(Order = 6)]
    public string post_text { get; set; }
}

Change the class and update the database and it will work fine

Upvotes: 2

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