Angular : Pass multiple class to Web Api post method Free Guide

In the realm of Web API development, passing data to a POST method is a common task. However, when dealing with more complex scenarios, where multiple classes need to be sent, the approach becomes nuanced. This article aims to provide a comprehensive guide on how to Pass multiple class to Web Api post method.

Why Pass multiple class to Web Api post method

Consider a scenario where you need to submit data that spans multiple classes. This could be a common occurrence in real-world applications, especially those dealing with intricate data models. Understanding how to structure and send these classes is essential for seamless communication between clients and APIs.

Web API Basics

Before diving into the specifics of passing multiple classes, let’s revisit some fundamental concepts of Web API development. This quick recap will set the stage for a more in-depth exploration of passing complex data.

Pass multiple class to Web Api post method

Single Class vs. Multiple Classes in POST Requests

To appreciate the significance of passing multiple classes, we’ll first compare the traditional approach of sending a single class with the more sophisticated method of handling multiple classes in POST requests.

Single Class:

  • Use a single class when your POST requests have a similar structure with just a few data fields.
  • This keeps things simple and avoids code duplication.


Imagine a system for creating new user accounts. A single CreateUserRequest class could hold all the necessary data:


class CreateUserRequest:
  def __init__(self, username, email, password):
    self.username = username = email
    self.password = password

Multiple Classes:

  • Use multiple classes when your POST requests have significantly different structures or involve complex data nesting.
  • This improves code readability, maintainability, and reduces the chance of errors.


Consider a system for placing orders. You might have separate classes for different order types:

  • CreateBasicOrderRequest: Contains basic information like customer ID and product IDs.
  • CreateBulkOrderRequest: Includes additional fields like total quantity and discount code.

class CreateBasicOrderRequest:
  def __init__(self, customer_id, product_ids):
    self.customer_id = customer_id
    self.product_ids = product_ids

class CreateBulkOrderRequest:
  def __init__(self, customer_id, product_ids, total_quantity, discount_code):
    self.customer_id = customer_id
    self.product_ids = product_ids
    self.total_quantity = total_quantity
    self.discount_code = discount_code

Here are some additional factors to consider:

  • Scalability: If you expect to add more complex request types in the future, using multiple classes allows for easier expansion.
  • Data Validation: Separate classes can have their own validation logic specific to the data they hold.
  • Documentation: Clear class names and separation make your API documentation more understandable.

Ultimately, the best approach depends on your specific needs. Choose the method that promotes code clarity, maintainability, and ease of use for your project.

Implementing Multiple Classes in Web API

This section will guide you through the steps of implementing the server-side logic to handle multiple classes. We’ll provide code examples and explain the necessary configurations to ensure smooth processing.


  • Improved code organization: Separating order details and potentially customer information into dedicated classes promotes cleaner and more maintainable code.
  • Reusability: Classes like OrderItem can be reused across different endpoints if needed.
  • Scalability: As your API grows, adding new order-related functionalities becomes easier with well-defined classes.

Remember, this is a basic example. You can adapt it to your specific data structure and API functionalities.

Serialization and Deserialization

Understanding how data is serialized and deserialized is crucial when dealing with multiple classes. We’ll discuss the role of serialization in preparing data for transmission and deserialization on the receiving end.


  • Process: Converting an in-memory object (like a .NET class instance) into a format suitable for transmission or storage. This format is often human-readable (JSON, XML) or binary for efficiency.
  • Purpose: Allows data to be exchanged between different systems or persisted for later use.


  • Process: Reversing serialization, taking the transmitted or stored data and converting it back into an in-memory object that the receiving system can understand and work with.

Benefits of Serialization and Deserialization

  • Platform Independence: Data can be exchanged between different programming languages and systems as long as they understand the chosen format (JSON, XML).
  • Efficiency: Serialized data is often more compact than the original object, reducing transmission costs and storage requirements.
  • Ease of Use: Web API frameworks handle serialization and deserialization automatically, simplifying development.

Additional Considerations

  • Security: Ensure proper validation of deserialized data to prevent security vulnerabilities like injection attacks.
  • Performance: For very large datasets, consider binary serialization formats if raw efficiency is crucial.
  • Customization: Frameworks often offer ways to customize serialization and deserialization behavior.

Handling Complex Objects

Passing multiple classes often involves dealing with complex objects. We’ll share tips and best practices for handling these intricacies within your Web API.

Scenario: Imagine a library web API that allows users to create new books. A book itself has properties like title, author, ISBN, and genre. Genre can be a separate entity with a name (e.g., “Fantasy”).

Complex Object: Book

Here’s the structure of the Book object we want to send to the web API:

  "title": "The Lord of the Rings",
  "author": "J. R. R. Tolkien",
  "isbn": "978-0261102694",
  "genre": {
    "name": "Fantasy"

Data Transfer with JSON

Web APIs typically rely on JSON (JavaScript Object Notation) to exchange data. JSON provides a lightweight and language-independent way to represent complex objects. In our case, the Book object with nested genre information gets converted to JSON format before sending it to the API.

API Endpoint for Creating Books

On the server-side, the web API will have an endpoint specifically designed to handle book creation requests. This endpoint might look something like:

POST /api/books

The POST method signifies creating a new resource (a book in this case).

Receiving and Processing the Complex Object

The web API controller method that handles the /api/books endpoint will be designed to receive the JSON data containing the book information. Here’s a simplified example (depending on the specific framework):


public class BooksController
  publicIActionResult CreateBook([FromBody] Book book)
      // Access book properties like title, author, etc.
      // Process book data and save it to the database

In this example, the [FromBody] attribute specifies that the book parameter should be retrieved from the request body (which will contain the JSON data). Now, the controller can access the book’s properties (title, author, etc.) and its nested genre object for further processing.

Benefits of Using Complex Objects

  • Reduced Number of Parameters: Instead of sending individual parameters for each book property, a complex object encapsulates everything, making the API cleaner and easier to use.
  • Improved Readability: The JSON format provides a clear structure for the book data, improving code readability on both the client and server sides.
  • Data Validation: The server-side code can perform validation on the entire complex object, ensuring all required data is present and in the correct format.

Things to Consider

  • Deeply Nested Objects: While complex objects are useful, excessively nested structures can make code complex. Consider breaking down functionalities into separate API endpoints if needed.
  • Versioning: If your API evolves with changes to the Book object structure, implement a versioning strategy to ensure compatibility with existing clients.

By following these practices, you can effectively handle complex objects within your web API design, leading to a more robust and maintainable system.

Client-Side Considerations

On the client side, structuring requests to send multiple classes requires attention to detail. We’ll explore how to format requests to ensure compatibility with the server.

  1. Data Formatting: The API might provide data in JSON format. The client-side JavaScript code needs to parse the JSON response to extract the relevant information like temperature and weather description. Libraries like Fetch API or Axios can simplify making HTTP requests and handling responses.
  2. Error Handling: What if the API request fails due to network issues or the server being unavailable? The client-side code should handle these errors gracefully. This might involve displaying an error message to the user or retrying the request after a delay.
  3. Security: Be cautious! Client-side JavaScript can be accessed and potentially modified by users. Sensitive API keys or access tokens should never be directly stored in the client-side code. Consider server-side authentication and passing required data securely to the client-side.
  4. Data Validation: Even though data comes from an API, it’s good practice to validate it on the client-side. For instance, the temperature value might be corrupt. You can check if the received value falls within a reasonable range for the user’s location.
  5. User Experience (UX): While fetching data, provide feedback to the user. Show a loading indicator while waiting for the API response. This keeps the user informed and avoids the impression of a frozen application.

// Fetch weather data using Fetch API
  .then(response => response.json())  // Parse JSON response
  .then(data => {
    const temp = data.main.temp; // Extract temperature in Kelvin
    const weather =[0].main; // Extract weather condition

    // Assuming we have HTML elements with IDs
    document.getElementById('temperature').textContent = convertKelvinToCelcius(temp);
    document.getElementById('weather').textContent = weather;
  .catch(error => {
    console.error('Error fetching weather data:', error);
    // Handle error, display message to user

// Function to convert Kelvin to Celsius (assuming this is needed)
function convertKelvinToCelcius(kelvin) {
  return (kelvin - 273.15).toFixed(1);

Error Handling

No system is without its challenges. We’ll address potential issues and provide strategies for effective error handling when dealing with multiple classes in Web API POST requests.

1. Error Types and HTTP Status Codes:

Web APIs leverage HTTP status codes to communicate errors. These codes are categorized as:

  • Client Errors (4xx): Indicate issues caused by the client’s request. Examples:
    • 400 (Bad Request): Invalid data format in the request body.
    • 401 (Unauthorized): Missing or invalid authentication credentials.
    • 404 (Not Found): Requested resource doesn’t exist.
  • Server Errors (5xx): Represent internal server problems. Examples:
    • 500 (Internal Server Error): Unexpected error on the server’s side.
    • 503 (Service Unavailable): Server is overloaded or under maintenance.

2. Throwing Exceptions:

Exceptions are commonly used to indicate errors within the API code. Specific exceptions can be thrown for different scenarios:


public class UserNotFoundException : Exception
    public UserNotFoundException(int userId) : base($"User with ID {userId} not found.")

This example defines a UserNotFoundException that gets thrown when a user with a specific ID isn’t found.

3. Returning Error Responses:

When an exception occurs, the API needs to return an informative error response to the client. Here’s an example using ASP.NET Web API:


public IActionResult GetUser(int id)
        var user = _userService.GetUser(id);
        if (user == null)
            throw new UserNotFoundException(id);
        return Ok(user);
    catch (UserNotFoundException ex)
        return NotFound(new { message = ex.Message });
    catch (Exception ex)
        // Handle generic errors (e.g., logging)
        return StatusCode(500);

In this example:

  • The GetUser method attempts to retrieve a user by ID.
  • If the user is not found, a UserNotFoundException is thrown.
  • The exception filter catches the UserNotFoundException and returns a 404 (NotFound) status code with a specific message in the response body.
  • A generic catch block handles any other exceptions and returns a 500 (Internal Server Error) status code.

4. Additional Considerations:

  • ProblemDetails: ASP.NET Core offers the ProblemDetails class for standardized error responses. It includes details like status code, title, and additional properties for specific errors.
  • Exception Filters: You can create custom exception filters to handle errors centrally and provide a consistent response format.

By implementing proper error handling, your Web API can communicate issues effectively to clients, improving debugging and overall application stability.

Security Best Practices

Ensuring the secure transmission of multiple classes is paramount. We’ll outline best practices to safeguard your data during transit.

1. Authentication and Authorization:

  • Concept: This is the foundation of API security. Authentication verifies a user’s identity (who they are), while authorization determines what actions they can perform (what they are allowed to do).
  • Example: An e-commerce API might use a username and password for authentication. Once a user logs in (authenticated), their authorization level determines if they can view product details (low level) or add new products (high level).
  • Implementation: There are various methods for authentication (OAuth, API keys) and authorization (role-based access control).

2. Encryption (HTTPS):

  • Concept: HTTPS encrypts data in transit between the API and client application, protecting it from eavesdropping.
  • Example: When a user submits a credit card number through an e-commerce API, HTTPS ensures the number is scrambled during transmission, making it unreadable to anyone intercepting the data.
  • Implementation: Enable HTTPS on your web server and ensure it uses strong ciphers and the latest TLS version.

3. Input Validation:

  • Concept: API endpoints should validate all user-provided data to prevent malicious attacks like SQL injection or cross-site scripting (XSS).
  • Example: A social media API should validate the content of a user’s post to ensure it doesn’t contain harmful code. It can reject posts containing script tags (<script>) commonly used in XSS attacks.
  • Implementation: Use libraries or frameworks that provide built-in data validation functionalities.

4. Rate Limiting and Throttling:

  • Concept: Limit the number of API requests a user or application can make within a specific timeframe to prevent Denial-of-Service (DoS) attacks.
  • Example: A stock trading API might limit the number of times a user can request stock price updates per minute to prevent overwhelming the server with excessive traffic.
  • Implementation: Configure API gateways or web servers to throttle requests based on IP address, API key, or other identifiers.

5. Logging and Monitoring:

  • Concept: Continuously monitor API activity for suspicious behavior and log all requests and responses for auditing purposes.
  • Example: An API might log details like the user making a request, the endpoint accessed, and the data transmitted. This helps identify unauthorized access attempts or unusual patterns.
  • Implementation: Use security information and event management (SIEM) tools to centralize log collection and analysis.

Bonus: Secure Coding Practices

  • Write secure code by following best practices to avoid common vulnerabilities like buffer overflows and insecure direct object references (IDOR).
  • Regularly update and patch your API software to address security flaws discovered by the development team or security researchers.

By following these security best practices and implementing the appropriate controls, you can significantly reduce the risk of attacks on your Web APIs and protect your valuable data.

Testing and Debugging

Testing and debugging become more critical when working with complex data structures. We’ll cover strategies to streamline the testing and debugging process.

1. API Design and Documentation:

  • Imagine an API endpoint GET /products/{id} that retrieves a product by its ID.
  • Document this endpoint clearly, specifying required parameters (like product ID) and expected response format (product details in JSON).

2. Testing Strategies:

  • Manual Testing:
    • Use tools like Postman to send a GET request with a valid product ID (e.g., ID: 123) and see if the response contains the expected product information (name, description, price etc.).
    • Try invalid data (e.g., negative ID or string) and ensure the API returns an appropriate error code (e.g., 400 Bad Request) with a clear error message.
  • Unit Testing:
    • Write unit tests that isolate and test functionalities of your API controllers and logic.
    • Test scenarios like successful product retrieval, handling non-existent product IDs, and database errors.
  • Integration Testing:
    • Test how the API interacts with other systems it relies on (e.g., database).
    • Simulate different scenarios and ensure data flows smoothly between the API and other components.

3. Debugging Techniques:

  • Error Logs:
    • Implement a logging mechanism to capture errors and exceptions that occur during API execution.
    • Analyze logs to pinpoint the root cause of issues (e.g., database connection failures, invalid data processing).
  • Breakpoints and Debuggers:
    • Use debuggers provided by your development environment (e.g., Visual Studio) to set breakpoints in your code.
    • Step through the code execution line by line, inspect variables, and identify where errors originate.

Example: Debugging a Product Not Found Error

  • Scenario: You test the GET /products/123 endpoint and receive a 404 Not Found error.
  • Debugging Steps:
    1. Check API logs for any related errors. Maybe the database query for product ID 123 failed.
    2. Set breakpoints in your code to trace the execution flow of the product retrieval logic.
    3. Use the debugger to step through the code and see if the product ID is being passed correctly to the database layer.
    4. If the ID is correct but the database returns no results, investigate the database itself for potential missing data or configuration issues.


  • Automate tests as much as possible for efficiency and repeatability. Tools like Jest or Mocha can help with unit and integration test automation.
  • Provide meaningful error messages in your API responses to aid developers in debugging issues.
  • Security testing is crucial. Ensure your API is protected against unauthorized access and vulnerabilities.

By following these strategies and techniques, you can effectively test and debug your Web APIs, ensuring they function reliably and deliver the expected results.

Real-World Examples

Model Class

public class MainClass
public IList<subClass1> sub1 { get; set; }
       public subClass2 sub2 { get; set; }       


public HttpResponseMessageUpdate([FromBody] MainClass mMain)


Service typescript File

Update (sub2:any, sub1: any []) {
        const headers = new Headers({
            'Content-Type': 'application/json',
            'Authorization': 'Bearer ' + this.sessionToken
               let options = new RequestOptions({ headers: headers });
              let body = JSON.stringify({sub1 :  sub1, sub2: sub2})
              return + 'api/Costing/ Update, body,
                      options).map(response =>