Deleting group of data from json array in c#

Question

Im trying to create a "Library Database" as part of a university project in ASP.Net & C#, With Json used as a storage method.

Im a complete newbie to asp.net and c#, Yesterday someone was helping me figure out how to fill a range of text boxes in a form with the relevant data from a Json array, when each element in that array is selected using a Drop Down List. We managed to get that part of the code up and running but ive hit a new roadblock.

I need to know how to delete a data entry in a JSON Array.

Below is the code with the variables for my Json array

public class Book
{
    public string id { get; set; }
    public string title { get; set; }
    public string author { get; set; }
    public string year { get; set; }
    public string publisher { get; set; }
    public string isbn { get; set; }

    public Book(string id, string title, string author, string year, string publisher, string isbn)
    {
        this.id = id;
        this.title = title;
        this.author = author;
        this.year = year;
        this.publisher = publisher;
        this.isbn = isbn;       
    }
}

Below is the code for my Array

public class BookList
{
    public List<Book> bookList { get; set; }

    public BookList()
    {
        bookList = new List<Book>();
    }

    public object Where(Func<object, bool> p)
    {
        throw new NotImplementedException();
    }
}

Below is the CURRENT Json Data

{
  "bookList": [
    {
      "id": "1",
      "title": "Harry Potter and the Philosopher's Stone",
      "author": "J.K. Rowling",
      "year": "1997",
      "publisher": "Bloomsbury",
      "isbn": "0-7475-3269-9"
    },
    {
      "id": "2",
      "title": "The Hobbit",
      "author": "J. R. R. Tolkien",
      "year": "1937",
      "publisher": "George Allen & Unwin",
      "isbn": "054792822X"
    },
    {
      "id": "3",
      "title": "Nisekoi: False Love",
      "author": "Naoshi Komi",
      "year": "2014",
      "publisher": "Viz",
      "isbn": "9781421557991"
    }
  ]
}

Below is the current Code for my delete book page

public partial class DeleteBook : System.Web.UI.Page
{
    public const string FILENAME = @"C:\Users\User\Documents\Assessments\19383038_CSE2ICX_Assignment3\JsonFiles\BookList.Json";
    string jsonText = File.ReadAllText(FILENAME);
    BookList bookList = new BookList();

    public void Page_Load(object sender, EventArgs e)
    {
        bookList = JsonConvert.DeserializeObject<BookList>(jsonText);
        if (!IsPostBack)
        {
            ddl.DataTextField = "id";
            ddl.DataValueField = "id";
            ddl.DataSource = bookList.bookList;
            ddl.DataBind();
        }

        var book = bookList.bookList.Where(x => x.id == ddl.SelectedValue).FirstOrDefault();
        txtDeleteID.Text = book.id;
        txtDeleteTitle.Text = book.title;
        txtDeleteAuthor.Text = book.author;
        txtDeleteYear.Text = book.year;
        txtDeletePublisher.Text = book.publisher;
        txtDeleteIsbn.Text = book.isbn;
    }

    protected void btnDeleteBook_Click(object sender, EventArgs e)
    {
        // ...
    }

    protected void btnClearField_Click(object sender, EventArgs e)
    {
        // ...
    }
}

So in the Page load, the code is telling each of the text boxes in my form to read what data each variable contains within the array with regards to what ID i have selected in the drop down list.

Now what i need to do is DELETE that data and only that data. I dont want to refer to the data by name specifically, as this data base will allow people to enter other data and i need a method that figures out what the data is called, then deletes it. This applies to all of the data within each book. For example, Harry potter is a book listed in this library and I want to delete all information pertaining to Harry Potter when i click on the delete book button.

Unfortunately I am not experienced enough with accessing the information in JSON properly, Ive tried converting the array into a jobject but haven't had any luck on that path. and the .REMOVE function only lets me handle Int's , could someone please help me with solving this problem, or understanding how to manipulate this data.

Sorry for the long post, and if what i want inst clear enough let me know and ill do my best to explain in more detail. Thank you in advance for any help received.

I would suggest that, after you deserialize the json you can remove it from the list then re-serialize the list to json — Mohammad Ali
– Mohammad Ali, Commented Mar 16, 2018 at 12:04
Is it one og them project requirements that you use JSON as storage? If not, you really should use a real DB — Krzysztof Skowronek
– Krzysztof Skowronek, Commented Mar 16, 2018 at 12:14
Ive already deserialized the json file in the page load? my problem is im not sure how to remove data from it even after that. — Lochlan Mckinnon
– Lochlan Mckinnon, Commented Mar 16, 2018 at 12:14
@KrzysztofSkowronek Yes unfortunately all data has to be stored in a JSON file, the idea isnt using a database but learning how to make one from scratch, even if ill probably never do that strictly in c#. — Lochlan Mckinnon
– Lochlan Mckinnon, Commented Mar 16, 2018 at 12:15

Camilo Terevinto · Accepted Answer · 2018-03-17 13:28:07Z

2

In your button click remove

protected void btnDeleteBook_Click(object sender, EventArgs e)
{
   var itemToRemove = bookList.bookList.FirstOrDefault(r => r.id == ddl.SelectedValue);
   if(itemToRemove != null)
      bookList.bookList.Remove(itemToRemove);
}

this will delete the selected book from the bookList. Now serialize the list back to json.

string newJsonText = JsonConvert.SerializeObject(bookList);

Also rename your bookList class to something else because bookList.bookList looks very confusing. Maybe bookStore or so

edited Mar 17, 2018 at 13:28

Camilo Terevinto

32.2k7 gold badges95 silver badges127 bronze badges

answered Mar 16, 2018 at 12:22

H.Mikhaeljan

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11 Comments

Lochlan Mckinnon Over a year ago

haha thanks good tip about the booklist, just doing it the way i learnt but ill start coming up with better names. EDIT: I needed to set it to bookList.booklist for it to r to recognise id. now when i ran the code there was an error when it reached remove. Ive been having issues with the remove function all night but everywhere says to use it. Am i doing something wrong elsewhere in the code?

H.Mikhaeljan Over a year ago

Eddited with bookList.bookList As i said its confusing hehe try the new version.

Lochlan Mckinnon Over a year ago

Allright, so. Hooray it deleted the third book entry. BUT there is another issue

Lochlan Mckinnon Over a year ago

EDIT: Ive just realised it deleted booklist and the opening/closing {} brackets as well. any idea how to stop it from doing this?

H.Mikhaeljan Over a year ago

You mean you rewrote the JSON? Maybe you made some mistake with the quotes?

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