3.6 KiB
Model validation & API Design
Model Validation
ASP.NET has a built-in system for validating whether the data sent in requests fits the model set in the code
Additional requirements can be set with attributes
public class Contact
{
public int Id { get; set; }
[Required]
[MaxLength(50)]
public string Name { get; set; }
[MaxLength(100)]
public string Email { get; set; }
}
Model Validation (continued)
An object can be validated at any time with TryValidateModel method:
[HttpPost]
public IActionResult Post([FromBody] Contact contact)
{
if (!TryValidateModel(contact))
{
return BadRequest(ModelState);
}
Contacts.Add(contact);
return Created(Request.Path, contact);
}
The attributes set a corresponding error message and information to the ModelState which is sent with the bad request result
Sometimes you might have custom requirements and the action should, according to the standard, return a bad request if the action does not fit those requirements
For example, the simplest possible way to validate the format of an email is to check whether it contains the '@' symbol and with AddModelError add an error if it does not:
if (!contact.Email.Contains('@'))
{
ModelState.AddModelError("Description", "The email is not in valid form.");
}
Then check the model state:
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
Exercise 1:
Continue working on CourseAPI.
Mark all the properties of the Course class with the [Required] attribute
Create an endpoint for POST requests with the URI api/courses
All the contents of the new course should come from the request body and the new course should be added to the Courses list
The maximum number of credits should be 20 and minimun 1 (Tip: Range)
Return an appropriate response
Model Validation - Limiting PATCH
- If we only want to allow the PATCH operation to affect Name and Email properties of Contact class
- Begin by declaring a class with only those fields:
- public class ContactPatch
- {
- public string Name { get; set; }
- public string Email { get; set; }
- }
Model Validation - Limiting PATCH (continued)
Use the ContactPatch class instead of the actual class for patching:
[HttpPatch("{id}")]
public IActionResult Patch(int id, [FromBody] JsonPatchDocument patchDocument)
{
Contact initialContact = _contactRepository.GetContact(id);
ContactPatch patchContact = new ContactPatch
{ Name = initialContact.Name, Email = initialContact.Email };
patchDocument.ApplyTo(patchContact, ModelState);
if (!ModelState.IsValid)
{
return BadRequest();
}
initialContact.Name = patchContact.Name;
initialContact.Email = patchContact.Email;
_contactRepository.UpdateContact(id, initialContact);
return Ok(initialContact);
}
Designing APIs
It's useful to get a good overview of the API for yourself and others before getting to work
| Method | Endpoint | Description | Success | Failure |
|---|---|---|---|---|
| GET | /api/contacts | Return all contacts | 200 Ok | 400 Bad request 404 Not found |
| POST | /api/contacts | Add a new contact | 201 Created | 400 Bad request |
| PUT | /api/contacts/{id} | Update a contact | 204 No content | 400 Bad request 404 Not found |
| PATCH | /api/contacts/{id} | Partially update a contact | 204 No content | 400 Bad request 404 Not found |
| DELETE | /api/contacts/{id} | Remove a contact | 200 OK | 404 Not found |