Todo App Backend Template
.NET — Schema, API & AI Guide

Key Takeaways

Overview

A Todo app is one of the most common starting points for learning backend development. Under the hood it needs user registration, task CRUD, ownership-based access control, and optionally real-time sync.

The schema below defines two classes — _User (built-in) and Todo — connected by a Pointer. With the Back4app .NET SDK, you can interact with this backend from your app — querying, creating, updating, and deleting objects — without writing a custom API layer.

Why Build Your .NET Todo Backend with Back4app?

Back4app fits .NET shops that need a reliable, deployable backend without managing infrastructure.

• •Parse .NET SDK: Use the official Parse SDK with Task and async/await; typed ParseObject and queries keep your C# code type-safe.
• •Enterprise stability: Deploy your .NET app against a hosted backend; Back4app handles scaling and availability.
• •Fits existing tooling: Integrate with Entity Framework patterns or use the SDK alone; REST and GraphQL are available for other clients.

Fits .NET shops using Entity Framework or standard async patterns.

Core Benefits

A production-ready Todo backend so you can ship faster and focus on your app.

Technical Stack

Everything powering this Todo app template at a glance.

ER Diagram

Entity-Relationship diagram for the .NET Todo app data model.

erDiagram
    _User {
        String objectId PK
        String username
        String email
        String password
        Date createdAt
        Date updatedAt
    }

    Todo {
        String objectId PK
        String title
        Boolean done
        Date dueDate
        Number priority
        Pointer owner FK
        Date createdAt
        Date updatedAt
    }

    _User ||--o{ Todo : "owns"

Integration Flow

Auth-to-CRUD sequence: how your .NET app talks to Back4app — login, then query and create todos.

sequenceDiagram
  participant User
  participant App as .NET App
  participant Back4app as Back4app Cloud

  User->>App: Login
  App->>Back4app: ParseUser.LogInAsync(username, password)
  Back4app-->>App: Session token
  App-->>User: Logged in

  User->>App: Load todos
  App->>Back4app: ParseObject.GetQuery("Todo").FindAsync()
  Back4app-->>App: IEnumerable<ParseObject>
  App-->>User: Show list

  User->>App: Create todo
  App->>Back4app: todo.SaveAsync()
  Back4app-->>App: Todo (ObjectId)
  App-->>User: Updated list

Data Dictionary

Complete field reference for every class in the schema.

Security & Permissions

How ownership, ACLs, and class-level permissions protect data in this schema.

Schema (JSON)

Raw JSON schema definition — copy and use in your Back4app app or import via the API.

{
  "classes": [
    {
      "className": "Todo",
      "fields": {
        "objectId": {
          "type": "String",
          "required": false
        },
        "title": {
          "type": "String",
          "required": true
        },
        "done": {
          "type": "Boolean",
          "required": false,
          "defaultValue": false
        },
        "dueDate": {
          "type": "Date",
          "required": false
        },
        "priority": {
          "type": "Number",
          "required": false,
          "defaultValue": 3
        },
        "owner": {
          "type": "Pointer",
          "targetClass": "_User",
          "required": false
        },
        "createdAt": {
          "type": "Date",
          "required": false
        },
        "updatedAt": {
          "type": "Date",
          "required": false
        }
      }
    },
    {
      "className": "_User",
      "fields": {
        "objectId": {
          "type": "String",
          "required": false
        },
        "username": {
          "type": "String",
          "required": true
        },
        "email": {
          "type": "String",
          "required": true
        },
        "password": {
          "type": "String",
          "required": true
        },
        "createdAt": {
          "type": "Date",
          "required": false
        },
        "updatedAt": {
          "type": "Date",
          "required": false
        }
      }
    }
  ]
}

API Playground

Try the REST and GraphQL endpoints for the Todo schema. Responses from the example data above — no Back4app account needed.

Uses the same Todo schema as this template.

Step-by-Step .NET Integration

Connect to your Back4app backend from a .NET app using the Back4app .NET SDK.

1. Step 1: Install Back4app .NET SDK

   Add the Back4app SDK for your stack (e.g. npm, pubspec, or package manager).

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   dotnet add package Parse

2. Step 2: Initialize Back4app in your app

   Initialize the Back4app SDK at app startup with your App ID and server URL.

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   // Startup or Program.cs
   ParseClient.Initialize(new ParseClient.Configuration
   {
       ApplicationId = "YOUR_APP_ID",
       Server = "https://parseapi.back4app.com/",
       WindowsKey = "YOUR_WINDOWS_KEY" // or use Key for REST
   });

3. Step 3: Query all todos

   Use the SDK to fetch all Todo objects, sorted by priority.

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   public static async Task<IEnumerable<ParseObject>> GetTodosAsync()
   {
       var query = ParseObject.GetQuery("Todo")
           .OrderBy("priority");
       return await query.FindAsync();
   }

4. Step 4: Create a todo

   Create a new Todo with title, done, and priority, then save.

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   public static async Task<ParseObject> CreateTodoAsync(string title, int priority = 3)
   {
       var todo = new ParseObject("Todo");
       todo["title"] = title;
       todo["done"] = false;
       todo["priority"] = priority;
       await todo.SaveAsync();
       return todo;
   }

5. Step 5: Update and delete todos

   Update fields and save, or delete the object.

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   public static async Task MarkDoneAsync(string objectId)
   {
       var todo = await ParseObject.GetQuery("Todo").GetAsync(objectId);
       todo["done"] = true;
       await todo.SaveAsync();
   }
   
   public static async Task DeleteTodoAsync(string objectId)
   {
       var todo = await ParseObject.GetQuery("Todo").GetAsync(objectId);
       await todo.DeleteAsync();
   }

Full Data Model

Copy a complete Todo model for type-safe serialization (e.g. class, interface, or type definition).

// Todo.cs — matches Back4app schema
public class Todo
{
    public string? ObjectId { get; set; }
    public string Title { get; set; } = "";
    public bool Done { get; set; }
    public DateTime? DueDate { get; set; }
    public int Priority { get; set; } = 3;
    public ParseUser? Owner { get; set; }
    public DateTime? CreatedAt { get; set; }
    public DateTime? UpdatedAt { get; set; }

    public static Todo From(ParseObject obj) => new Todo
    {
        ObjectId = obj.ObjectId,
        Title = obj.Get<string>("title") ?? "",
        Done = obj.Get<bool>("done"),
        DueDate = obj.Get<DateTime?>("dueDate"),
        Priority = obj.Get<int>("priority"),
        Owner = obj.Get<ParseUser>("owner"),
        CreatedAt = obj.CreatedAt,
        UpdatedAt = obj.UpdatedAt
    };
}

Frequently Asked Questions

Common questions about the Todo app backend template.