HttpClientFactory | safe HttpClient For netcore And netframework | HTTP Client library

If you just post singal request.there's even no difference between injecting an instance of httpclient and creating a instance of httpclient with httpclientfactory .

if you use serval instance of httpclient or reuse httpclient to post mutiple requests,some problems may occor,using httpclient could handle these problems. You could create httpclients with differenet settings as follow:

in startup.cs:

1. Will it use HttpClientFactory to create an instance of HttpClient?

Yes. A default HttpClient is registered as a transient service during HttpClientFactory registration.

1. I guess it uses HttpClientFactory but will it have issues with DNS changes in that case?

Correct, it still would. As you inject it into a singleton, HttpClient here will be created only once. In order to make use of HttpClientFactory's HttpMessageHandler pooling, you'd need your HttpClients to be short-lived. So, for this you would rather need to inject IHttpClientFactory itself and call CreateClient when you need one. (Note that short-living HttpClients only apply to HttpClientFactory usage). BTW switching to a typed client will not help when injecting into a singleton, HttpClient will still end up being created only once, see https://github.com/dotnet/runtime/issues/64034.

Also, you can actually avoid HttpClientFactory entirely and still have DNS changes respected. For that you may have a static/singleton HttpClient with PooledConnectionLifetime set to some reasonable timeout (e.g. the same 2 minutes HttpClientFactory does)

I would really recommend that you not execute a five minute delay in your API controller. It will give you more grief than it's worth. For example, when IIS restarts your AppPool, it will wait up to 90 seconds for requests to process. During these autonomous restarts, this request will be aborted.

The problem server may have TCP KeepAlive set to Microsoft's recommended (but not default) value of 5 minutes. Because the HttpClient doesn't implement TCP keepalives by default, the problem server OS is likely disconnecting the TCP socket before the response is sent to the client because the client fails to respond to the keepalive being sent by the problem server OS.

You could adjust the TCP KeepAlive setting at the OS level on the problem server by editing the HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters\ subkey as described here.

Alternatively, you can configure the client to support TCP keepalive before sending the request by configuring the ServicePoint. If there is a network device, such as a stateful firewall, between the client and server, a high frequency keep-alive setting may help keep the connection open.

All you need to do is to specify the HttpResponseMessage as a return type when you declare your policy.

I'm pretty much sure that you are calling CreateClient without providing the client name. Try next in your ServiceWrapper:

Well this will work when there are more than 0 items (basket is not empty) but not when the basket is empty as:

Might you be looking for a constructor that takes two arguments?

When making an instance of the OrderLine type, you're using the Object Initializer syntax. However, because you explicitly made a Constructor with non-zero arguments, you must call that first.

Turns out it was a problem with JsonSerializer. The following changes did the trick for me: