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Controller

Controllers/ItemsController.cs

[Produces("application/json")]  // force le format JSON
[Route("api/[controller]")]     // /api/items
[ApiController]
public class ItemsController : ControllerBase
{
    private readonly IMyAppRepository _repository;

    public ListApiController(IMyAppRepository repository)
    {
        _repository = repository;
    }

GET

// [HttpGet("[action]")]
[HttpGet]
[ProducesResponseType(StatusCodes.Status200OK, Type = typeof(IEnumerable<Item>))]
public IActionResult Get() => Ok(_repository.GetAllItems());

[HttpGet("{id:int}")]
[ProducesResponseType(StatusCodes.Status200OK, Type = typeof(Item))]
[ProducesResponseType(StatusCodes.Status404NotFound)]
[ProducesResponseType(StatusCodes.Status500InternalServerError)]
public IActionResult Get(int id)
{
    try
    {
        var item = _repository.Get(id);
        if (item == null)
            return NotFound();  // status 404 Not Found

        return Ok(item);  // status 200 OK
    }
    catch (Exception ex)
    {
        // using Microsoft.AspNetCore.Http;
        return StatusCode(StatusCodes.Status500InternalServerError, $"Failed to get Item {id} ({ex})");
    }
}

POST

[HttpPost]
[ProducesResponseType(StatusCodes.Status201Created, Type = typeof(Item))]
[ProducesResponseType(StatusCodes.Status400BadRequest)]
[ProducesResponseType(StatusCodes.Status500InternalServerError)]
public IActionResult Post([FromBody] Item item)
{
    //if (item == null)
    //    return BadRequest();

    //if (!ModelState.IsValid)
    //    return BadRequest(ModelState);

    var createdItem = _itemRepository.Add(item);
    return Created("item", createdItem);

    return Created($"https://localhost:5001/api/items/{item.Id}", item);
    return CreatedAtAction(nameof(Get), new { id = item.Id }, item);
    return CreatedAtRoute("api", new { 
        controller =  "items", 
        action = nameof(Get), 
        id = $"{item.Id}" 
    }, item);
}

Startup.cs

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    app.UseMvc(routes => {
        routes.MapRoute(
            name: "api",
            template: "api/{controller=Items}/{id?}");
    });

PUT / Update

[ProducesResponseType(StatusCodes.Status204NoContent)]
[ProducesResponseType(StatusCodes.Status400BadRequest)]
[ProducesResponseType(StatusCodes.Status404NotFound)]
public IActionResult Put([FromBody] Item item)
{
    //if (item == null)
    //    return BadRequest();

    //if (!ModelState.IsValid)
    //    return BadRequest(ModelState);

    var itemToUpdate = _itemRepository.Get(item.Id);
    if (itemToUpdate == null)
        return NotFound();  // status 404 Not Found

    _itemRepository.Update(item);
    return NoContent();
}

DELETE

[HttpDelete("{id:int}")]
[ProducesResponseType(StatusCodes.Status204NoContent)]
[ProducesResponseType(StatusCodes.Status400BadRequest)]
[ProducesResponseType(StatusCodes.Status404NotFound)]
public IActionResult Delete(int id)
{
    if (id <= 0)
    {
        // do not provide details
        return BadRequest();
        // return a string instead of ProblemDetails
        return BadRequest("id must be greater than 0.");
        // same as BadRequest() but with detail
        return Problem(
            title: "Bad Request",
            detail: "id must be greater than 0.",
            statusCode: StatusCodes.Status400BadRequest);
    }

    var itemToDelete = _itemRepository.Get(id);
    if (itemToDelete == null)
        return NotFound();

    _itemRepository.Remove(id);
    return NoContent();
}

Client

Services/ItemDataService.cs

public class ItemDataService : IItemDataService
{
    private readonly HttpClient _httpClient;

    // injection de HttpClient
    public ItemDataService(HttpClient httpClient)
    {
        _httpClient = httpClient;
    }

GET

public async Task<IEnumerable<Employee>> GetAllItemsAsync()
{
    return await JsonSerializer.DeserializeAsync<IEnumerable<Item>>(
        await _httpClient.GetStreamAsync($"api/item"),
        new JsonSerializerOptions()
        {
            PropertyNameCaseInsensitive = true
        });
}

public async Task<Item> GetItemAsync(int itemId)
{
    return await JsonSerializer.DeserializeAsync<Item>(
        await _httpClient.GetStreamAsync($"api/item/{itemId}"),
        new JsonSerializerOptions()
        {
            PropertyNameCaseInsensitive = true
        });
}

POST

public async Task<Item> AddItemAsync(Item item)
{
    var itemJson =
        new StringContent(JsonSerializer.Serialize(item), Encoding.UTF8, "application/json");

    var response = await _httpClient.PostAsync("api/item", itemJson);

    if (response.IsSuccessStatusCode)
    {
        return await JsonSerializer.DeserializeAsync<Item>(await response.Content.ReadAsStreamAsync());
    }

    return null;
}

PUT

public async Task UpdateItemAsync(Item item)
{
    var itemJson =
        new StringContent(JsonSerializer.Serialize(item), Encoding.UTF8, "application/json");

    await _httpClient.PutAsync("api/item", itemJson);
}

DELETE

public async Task DeleteItemAsync(int itemId)
{
    await _httpClient.DeleteAsync($"api/item/{itemId}");
}

Validation

ItemViewModel.cs

public class ItemViewModel
{
    public int Id { get; set; }
    [Required]
    [MinLength(6)]
    public string Name { get; set; }
}

[HttpPost]
public IActionResult Post([FromBody]ItemViewModel itemVm)
{
    // ce code n'est plus nécessaire car pris en charge par les automatic HTTP 400 responses
    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }

    var item = itemVm.ToEfItem();
    _repository.Add(item);
    if (_repository.SaveAll())
    {
        var newItemVm = new ItemViewModel(item);
        return Created($"/api/ListApi/{newItemVm.Id}", newItemVm);
    }
    else
    {
        return BadRequest("Failed to save.");
    }

L'attribut [ApiController] effectue automatiquement une validation du modèle et envoie une réponse HTTP 400 en cas d'erreur.
Il n'est donc plus nécessaire de tester ModelState.IsValid.
ASP.NET Core MVC utilise le filtre d'action ModelStateInvalidFilter pour tester la validité du modèle.
Exemple de réponse en cas d'erreur de validation du modèle:

{
    "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
    "title": "One or more validation errors occurred.",
    "status": 400,
    "traceId": "|b659be6b-4fc34f5e9f3caf17.",
    "errors": {
        "Name": [
            "The Name field is required."
        ]
    }
}

// déserialiser la réponse
var validationProblem = await JsonSerializer.DeserializeAsync<ValidationProblemDetails>(
    await response.Content.ReadAsStreamAsync());

Query Strings

Url: http://localhost:80/api/items?option1=true

ItemsController.cs

[HttpGet]
public IActionResult Get(bool option1 = false)  // par défaut à false
{ }

Images

Download

MyController.cs

[HttpGet]
public IActionResult Get()
{
    var filePath = Path.Combine("~", "folder", "image.jpeg");
    // VirtualFileResult
    return File(filePath, "image/jpeg");
}

Base64

MyController.cs

[HttpGet]
public IActionResult Get()
{
    var filePath = Path.Combine("~", "folder", "image.jpeg");
    byte[] bytesArray = System.IO.File.ReadAllBytes(filePath);
    return Ok("data:image/jpeg;base64," + Convert.ToBase64String(bytesArray));
}

Upload

MyController.cs

[HttpPost]
public async Task<IActionResult> Post([FromForm]IFormFile myFile)
{
    var filePath = Path.Combine(folderPath, photo.FileName);
    using (var stream = new FileStream(filePath, FileMode.Create))
    {
        await myFile.CopyToAsync(stream);
    }

    return Ok(filePath);
}

Postman → Body → form-data

key: myFile
File
Value: Choose Files

Si myFile est toujours null, enlever [FromForm]

Renvoyer le message d'erreur des exceptions

ExceptionFilterAttribute

ApiExceptionFilterAttribute.cs

public class ApiExceptionFilterAttribute : ExceptionFilterAttribute
{
    public override void OnException(ExceptionContext context)
    {
        context.HttpContext.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
        context.HttpContext.Response.ContentType = "text/plain";
        context.HttpContext.Response.WriteAsync(context.Exception.Message).ConfigureAwait(false);
    }
}

MyController.cs

[ApiExceptionFilter]
[Route("api/[controller]")]
public class MyController : Controller

ExceptionMiddleware

ExceptionMiddleware.cs

public class ExceptionMiddleware
{
    public async Task Invoke(HttpContext context)
    {
        context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;

        var ex = context.Features.Get<IExceptionHandlerFeature>()?.Error;
        if (ex == null) return;

        context.Response.ContentType = "text/plain";
        await context.Response.WriteAsync(ex.Message);
    }
}

Startup.cs

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    app.UseExceptionHandler(new ExceptionHandlerOptions 
    {
        ExceptionHandler = new ExceptionMiddleware().Invoke
    });

    app.UseMvc();

Différencier la gestion d'erreur pour mvc et webapi

Utiliser un ApiExceptionFilterAttribute et un MvcExceptionFilter

UseWhen et UseExceptionHandler

Startup.cs

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    app.UseWhen(x => x.Request.Path.Value.StartsWith("/api"), builder =>
    {
        builder.UseExceptionHandler(new ExceptionHandlerOptions 
        {
            ExceptionHandler = new ExceptionMiddleware().Invoke
        });
    });
    app.UseWhen(x => !x.Request.Path.Value.StartsWith("/api"), builder =>
    {
        builder.UseExceptionHandler("/Home/Error");
    });

UseExceptionHandler

ExceptionMiddleware.cs

public class ExceptionMiddleware
{
    public async Task Invoke(HttpContext context)
    {
        if (context.Request.Path.Value.StartsWith("/api"))
        {
            context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;

            var ex = context.Features.Get<IExceptionHandlerFeature>()?.Error;
            if (ex == null) return;

            context.Response.ContentType = "text/plain";
            await context.Response.WriteAsync(ex.Message).ConfigureAwait(false);
        }
        else
        {
            // redirect to /Home/Error
        }
    }
}

UseStatusCodePagesWithReExecute

Startup.cs

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    app.UseStatusCodePagesWithReExecute("/error/{0}");
    app.UseExceptionHandler("/error/500");

    app.UseMvc();

[HttpGet("/error/{code:int}")]
public string Error(int code)
{
    return $"Error: {code}";
}

Erreurs

Unsupported Media Type with Postman

Body → raw = json à envoyer
Headers → Content-Type = application/json

JsonSerializationException: Self referencing loop detected for property 'xxx' ...

Startup.cs

services.AddMvc()
    // ignorer les références circulaires entre objets dans EF pour JSON
    .AddJsonOptions(opt => opt.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore);

SqlException: Cannot insert explicit value for identity column in table 'xxx' when IDENTITY_INSERT is set to OFF

Impossible de sauvegarder les changements si une entité a été insérée avec une valeur ≠ default dans une propriété bindée avec une colonne Identity.
Solution: forcer la valeur de cette propriété a default. La bdd mettra la valeur de la propriété a jour après avoir inséré l'entité.

Asp.net core web api

Sommaire

Liens

Projet

Controller

GET

POST

PUT / Update

DELETE

Client

GET

POST

PUT

DELETE

Validation

Automatic HTTP 400 responses

Query Strings

Images

Download

Base64

Upload

Renvoyer le message d'erreur des exceptions

ExceptionFilterAttribute

ExceptionMiddleware

Différencier la gestion d'erreur pour mvc et webapi

Utiliser un ApiExceptionFilterAttribute et un MvcExceptionFilter

UseWhen et UseExceptionHandler

UseExceptionHandler

UseStatusCodePagesWithReExecute

Erreurs

Unsupported Media Type with Postman

JsonSerializationException: Self referencing loop detected for property 'xxx' ...

SqlException: Cannot insert explicit value for identity column in table 'xxx' when IDENTITY_INSERT is set to OFF

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