Common mistakes

Common mistakes

Table 10.4 lists the mistakes most often made when creating and consuming web services.

Table 10.4. Common mistakes when working with web services

Problem	Cause	Fix
a nonexistent resource returns 500 or 200 with null	the handler does not check the lookup result	Results<Ok<T>, NotFound> and TypedResults.NotFound()
invalid JSON in Development gives 500	BadHttpRequestException is caught by the exception handler	a StatusCodeSelector returns bad.StatusCode
validation does not trigger	there is no AddValidation(), or the attributes are on the entity rather than on the parameter or DTO	register validation, annotate the DTO
the client gets Title instead of title, or numbers instead of names	different JSON settings on the server and the client	JsonSerializerOptions.Web and the same JsonStringEnumConverter
InvalidOperationException about concurrent use of a DbContext	the context or repository is registered as Singleton	AddDbContext (Scoped) and AddScoped for the repository
socket exhaustion under load	new HttpClient() for every request	IHttpClientFactory, a typed client
the application "hangs" during a request	.Result or .Wait() instead of await	asynchronous methods with await all the way up the chain