ASP.Net Core: FromForm, FromBody, and FromQuery

When working with APIs, it's common to receive data from different sources such as form submissions, request bodies, or query parameters. In ASP.Net Core, you can use the FromForm, FromBody, and FromQuery attributes to bind incoming data to action method parameters easily. In this article, we'll explore these attributes and provide examples to illustrate their usage.

FromForm

The FromForm attribute is used to bind data from form submissions to action method parameters. It tells the ASP.Net Core framework to look for data in the request's form collection and bind it to the corresponding parameters. Let's see an example:

[HttpPost]
public IActionResult SubmitForm([FromForm] MyFormModel model)
{
    // Process the submitted form data
    // ...
    return View();
}

In this example, the SubmitForm action method is decorated with the HttpPost attribute, indicating that it handles POST requests. The FromForm attribute is applied to the MyFormModel parameter, indicating that the model should be populated with data from the form submission.

FromBody

The FromBody attribute is used to bind data from the request body to action method parameters. It allows you to receive data in various formats such as JSON, XML, or plain text. Here's an example:

[HttpPost]
public IActionResult ProcessData([FromBody] MyDataModel model)
{
    // Process the received data
    // ...
    return Ok();
}

In this example, the ProcessData action method is also decorated with the HttpPost attribute to handle POST requests. The FromBody attribute is applied to the MyDataModel parameter, indicating that the model should be populated with data from the request body.

FromQuery

The FromQuery attribute is used to bind data from query parameters to action method parameters. It allows you to extract values directly from the URL's query string. Consider the following example:

[HttpGet]
public IActionResult Search([FromQuery] string searchTerm)
{
    // Perform a search based on the provided query parameter
    // ...
    return View();
}

In this example, the Search action method is decorated with the HttpGet attribute to handle GET requests. The FromQuery attribute is applied to the searchTerm parameter, indicating that the value should be extracted from the query string.

Combining Attributes

You can also combine these attributes to handle scenarios where you expect data from multiple sources. For instance, you might have an action method that accepts data from both the request body and query parameters. Here's an example:

[HttpPost]
public IActionResult ProcessData([FromBody] MyDataModel model, [FromQuery] string searchTerm)
{
    // Process the received data and perform a search
    // ...
    return Ok();
}

In this example, the ProcessData action method is decorated with both FromBody and FromQuery attributes. The MyDataModel parameter is bound to the request body, while the searchTerm parameter is extracted from the query string.

Conclusion

The FromForm, FromBody, and FromQuery attributes in ASP.Net Core provide convenient ways to bind incoming data to action method parameters. By utilizing these attributes, you can easily handle form submissions, request bodies, and query parameters in your API endpoints. Remember to use the appropriate attribute based on the data source you expect and combine them as needed for more complex scenarios.