In the previous post, we have handled different GET requests with the help of a DTO object. In this post, we are going to create POST PUT DELETE requests and by doing so we are going to complete the server part (.NET Core part) of this series.
Let’s get into it.
Let’s get right into it.
Handling POST Request
Firstly, let’s modify the decoration attribute for the action method GetOwnerById
in the Owner controller:
With this modification, we are setting the name for the action. This name will come in handy in the action method for creating a new owner.
we use the model class just to fetch the data from the database, to
return the result we need a DTO. It is the same for the create action.
So, let’s create the OwnerForCreationDto
class in the Entities/DataTransferObjects folder:
As you can see, we don’t have the Id and Accounts properties.
We are going to continue with the interface modification:
After the interface modification, we are going to implement that interface:
Before we modify the OwnerController, we have to create an additional mapping rule:
CreateMap<OwnerForCreationDto, Owner>();
Lastly, let’s modify the controller:
Right now is a good time to test this code by sending the POST request by using Postman.
Code Explanation
Let’s talk a little bit about this code. The interface and the repository parts are pretty clear so we won’t talk about that. But the code in the controller contains several things worth mentioning.
The CreateOwner
method has its own [HttpPost]
decoration attribute, which restricts it to the POST requests. Furthermore, notice the
owner parameter which comes from the client. We are not collecting it
from Uri but from the request body. Thus the usage of the [FromBody]
attribute. Also, the owner object is a complex type and because of that, we have to use [FromBody]
.
If we wanted to, we could explicitly mark the action to take this parameter from the Uri by decorating it with the [FromUri]
attribute, though I wouldn’t recommend that at all due to the security reasons and complexity of the request.
Since the owner
parameter comes from the client, it
could happen that the client doesn’t send that parameter at all. As a
result, we have to validate it against the reference type’s default
value, which is null.
Further down the code, you can notice this type of validation: if(!ModelState.IsValid)
. If you look at the owner model properties: Name
, Address
, and DateOfBirth
, you will notice that all of them are decorated with Validation Attributes. If for some reason validation fails, the ModelState.IsValid
will return false as a result, signaling that something is wrong with
the creation DTO object. Otherwise, it will return true which means that
values in all the properties are valid.
We have two map actions as well. The first one is from the OwnerForCreationDto type to the Owner type because we accept the OwnerForCreationDto object from the client and we have to use the Owner object for the create action. The second map action is from the Owner type to the OwnerDto type, which is a type we return as a result.
The last thing to mention is this part of the code:
CreatedAtRoute
will return a status code 201, which stands for Created
as explained in our post: The HTTP Reference. Also, it will populate the body of the response with the new owner object as well as the Location
attribute within the response header
with the address to retrieve that owner. We need to provide the name of
the action, where we can retrieve the created entity:
If we copy this address and paste it in Postman, once we send the GET request, we are going to get a newly created owner object.
Handling PUT Request
Excellent.
Let’s continue with the PUT request, to update the owner entity.
First, we are going to add an additional DTO class:
We did the same thing as with the OwnerForCreationDto
class. Even though this class looks the same as the OwnerForCreationDto
,
they are not the same. First of all, they have a semantical difference,
this one is for update action and the previous one is for creation.
Additionally, the validation rules that apply for the creation of DTO
don’t have to be the same for the update DTO. Therefore, it is always a
good practice to separate those.
One more thing, if you want to remove the code duplication from the OwnerForCreationDto
and OwnerForUpdateDto
,
you can create an additional abstract class, extract properties to it
and then just force these classes to inherit from the abstract class.
Due to the sake of simplicity, we won’t do that now.
After that, we have to create a new map rule:
CreateMap<OwnerForUpdateDto, Owner>();
Then, let’s change the interface:
Of course, we have to modify the OwnerRepository.cs
:
Finally, alter the OwnerController
:
As you may have noticed, the action method is decorated with the [HttpPut]
attribute. Furthermore, it receives two parameters: id of the entity we
want to update and the entity with the updated fields, taken from the
request body. The rest of the code is pretty simple. After the
validation, we are pulling the owner from the database and executing the
update of that owner. Finally, we return NoContent
which stands for the status code 204:
You can read more about Update actions in ASP.NET Core with EF Core to get a better picture of how things are done behind the scene. It could be very useful to upgrade quality of the update actions.
Handling DELETE Request
For the Delete request, we should just follow these steps:
Interface:
OwnerRepository:
OwnerController:
Let’s handle one more thing. If you try to delete the owner that has accounts, you are going to get 500 internal errors because we didn’t allow cascade delete in our database configuration. What we want is to return a BadRequest. So, to do that let’s make a couple of modifications.
Modify the IAccountRepository
interface:
Then modify the AccountRepository
file by adding one new method:
Finally, modify the DeleteOwner
action in the OwnerController
by adding one more validation before deleting the owner:
So, that is it. Send the Delete request from Postman and see the result. The owner object should be deleted from the database.
We have created these actions that use Repository Pattern logic synchronously but it could be done asynchronously as well. If you want to learn how to do that you can visit Implementing Async Repository in .NET Core. Although we strongly recommend finishing all the parts from this series for an easier understanding of the project’s business logic.
Also, in all these actions we are using try-catch blocks to handle our errors. You can do that in a more readable and maintainable way by introducing the Global Error Handling feature.
Conclusion
Now that you know all of this, try to repeat all the actions but for the Account entity. Because nothing beats the practice, doesn’t it? 😉
With all this code in place, we have a working web API that covers all the features for handling the CRUD operations.
By reading this post you’ve learned:
- The way to handle the POST request
- How to handle PUT request
- How to write better and more reusable code
- And the way to handle DELETE request
Thank you for reading and I hope you found something useful in it.
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