Retrieve the data under the header of a specified JSON text file under Blazor web application

Question

The GetFromJsonAsync method can be used to read data from a JSON text file into a variable in a Blazor web application. The method works well for simple JSON files.

Example for GetFromJsonAsync method:

@code {
    private Students[]? students;

    protected override async Task OnInitializedAsync()
    {
        students = await Http.GetFromJsonAsync<Students[]>("school.json");
    }

    public class Students
    {
        public int id { get; set; }
        
        public string? name { get; set; }
        
        public string? lastname { get; set; }

    }
}

My question is, how can I read only the data in a given JSON header?

Example:

{
   "book":[
      {
         "id":"444",
         "language":"C",
         "edition":"First",
         "author":"Dennis Ritchie "
      },
      {
         "id":"555",
         "language":"C++",
         "edition":"second",
         "author":" Bjarne Stroustrup "
      }
   ]
  "student": [ 
     { 
        "id":"01", 
        "name": "Tom", 
        "lastname": "Price" 
     }, 
    
     { 
        "id":"02", 
        "name": "Nick", 
        "lastname": "Thameson" 
     } 
  ]     
}

I only would like to read the data under the "student" JSON header into a students variable.

Update: According to Yong Shun's response, if only the data in the "student" JSON header is needed, it may be sufficient to create only the Student and the Root classes:

@code {
    private Student[]? students;

    protected override async Task OnInitializedAsync()
    {   
        Root? root = await Http.GetFromJsonAsync<Root>("school.json");
        students = root.Student.ToArray();
    }

    public class Student
    {
        [JsonPropertyName("id")]
        public string? Id { get; set; }

        [JsonPropertyName("name")]
        public string? Name { get; set; }

        [JsonPropertyName("lastname")]
        public string? Lastname { get; set; }
    }

    public class Root
    {
        [JsonPropertyName("student")]
        public List<Student>? Student { get; set; }
    }
}

https://stackoverflow.com/questions/36353470/search-array-of-a-class-c-sharp — Hans Passant, Apr 17 '22 at 06:37

score 1 · Accepted Answer · answered Apr 17 '22 at 06:43

You need a Root class. And suggest naming the property names as Pascal case and using the JsonPropertyName attribute

public class Book
{
    [JsonPropertyName("id")]
    public string Id { get; set; }

    [JsonPropertyName("language")]
    public string Language { get; set; }

    [JsonPropertyName("edition")]
    public string Edition { get; set; }

    [JsonPropertyName("author")]
    public string Author { get; set; }
}

public class Student
{
    [JsonPropertyName("id")]
    public string Id { get; set; }

    [JsonPropertyName("name")]
    public string Name { get; set; }

    [JsonPropertyName("lastname")]
    public string Lastname { get; set; }
}

public class Root
{
    [JsonPropertyName("book")]
    public List<Book> Book { get; set; }

    [JsonPropertyName("student")]
    public List<Student> Student { get; set; }
}

Deserialize the JSON as Root object.

protected override async Task OnInitializedAsync()
{
   Root root = await Http.GetFromJsonAsync<Root>("school.json");
   students = root.Students;
}

Retrieve the data under the header of a specified JSON text file under Blazor web application

1 Answers1