How to Properly Pass JSON POST Data to a Web API Method as an Object?

How to Pass JSON POST Data to Web API Method as an Object?

ASP.NET MVC4 Web API applications offer a convenient way to define POST methods that save customer data. However, when customer data is passed in JSON format within the POST request body, the customer parameter in the POST method might contain null values for its properties.

Fixing the Issue: Using Content Type "application/json"

To resolve this issue, it's crucial to use the following Content-Type header:

Content-Type: application/json

Request Modification:

When sending the request, the following changes are necessary:

// Convert the customer object to a JSON string
var customerJSON = JSON.stringify(customer);

// Set the Content-Type header
var xhr = new XMLHttpRequest();
xhr.open("POST", "api/customers");
xhr.setRequestHeader("Content-Type", "application/json");
xhr.send(customerJSON);

In this scenario, the model binder will appropriately bind the JSON data to the class object.

Additional Considerations:

• Ensure that the web API method parameter is decorated with the [FromBody] attribute:

public object Post([FromBody] Customer customer)

• If sending complex objects such as view models with nested properties, decorate the method parameter with [FromBody] and specify the Content-Type header as "application/json."
• If the above steps fail, ensure that the model properties are public and have a parameterless constructor. Also, verify that the property names match the JSON property names.

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