Singleton HttpClient handling - dotnet-httpclient

Question

I am using a singleton instance of HttpClient to make my calls. I was wondering is there a way to test if the HttpClient is valid? Can this instance of HttpClient go bad during the life of the application where there would be a need to create a new instance. My code is as follows
public class HttpClientWrapper : IHttpClientWrapper
{
private Uri _baseAddress;
private int _connectionTimeout;
private HttpClient _httpClientInstance;
private HttpClient HttpClientInstance
{
get
{
if (_httpClientInstance == null)
_httpClientInstance = CreateHttpClient();
return _httpClientInstance;
}
}
public HttpClientWrapper(Uri baseAddress, int connectionTimeout)
{
_baseAddress = baseAddress;
_connectionTimeout = connectionTimeout;
}
public Task<HttpResponseMessage> PostAsJsonAsync<T>(string requestUri, T value)
{
//Test the instance before using it. What should be the test??
return HttpClientInstance.PostAsJsonAsync<T>(requestUri, value);
}
private HttpClient CreateHttpClient()
{
HttpClientHandler handler = new HttpClientHandler()
{
UseDefaultCredentials = true
};
HttpClient client = new HttpClient(handler);
client.Timeout = TimeSpan.FromMilliseconds(_connectionTimeout);
client.BaseAddress = _baseAddress;
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
return client;
}
}

Answer 1

HttpClient is designed to be reused. It is not like the old days with WCF and ChannelFactory where the channel could become in a faulted state and had to be recreated.
HttpClient is intended to be instantiated once and re-used throughout the life of an application. Especially in server applications, creating a new HttpClient instance for every request will exhaust the number of sockets available under heavy loads. This will result in SocketException errors.
Ref: https://www.asp.net/web-api/overview/advanced/calling-a-web-api-from-a-net-client