Best practices for using HttpClient in c#

Introduction

HttpClient is the library to Get, Post, Put,.. and call WebAPIs and it is very important to use it correctly.
This Library has some methods to call web apis which all of them are Async. It is really important to use them in async method but if you are using an Async method in a console application that does not have separate UI thread you can use it like the following code :

public void MySyncMethod()
{
    using (HttpClient client = new HttpClient())
    {
        client.BaseAddress = new Uri("https://google.com");
        var response = client.GetAsync("SomeAddress").ConfigureAwait(false).GetAwaiter().GetResult();
        if (response.IsSuccessStatusCode)
        {
            //Do Something...   
        }
    }
}

Using ConfigureAwait(false) is very important for the applications 

which does not have separate UI thread

Creating HttpClient for each request is not a good Idea and Reuse Httpclient as much as possible.  But you need to do it for calling deferent urls. So what we have to do ?

It is easy, if you look at the constructor of the HttpClient signiture you can see it accepts 2 parameters:

public HttpClient (HttpMessageHandler handler, bool disposeHandler);

HttpMessageHandler is your connection manager ! if you do not dispose this object and recreate HttpClient for each request it solves you performance issue.

private static HttpClientHandler clientHandler = new HttpClientHandler();
public async Task MySyncMethod()
{
    using(HttpClient client = new HttpClient(clientHandler,false ))
    {
        client.BaseAddress = new Uri("https://google.com");
        var response = await client.GetAsync("SomeAddress");
        if (response.IsSuccessStatusCode)
        {
            
        }
    }
}

If you are going to use same url for several time you can use http client more than one and it is good ida to keep it alive. But if you have deferent request you should use Using Pattern and let HttpClient recreate for each Unique Url. You can have a dictionary of HttpClients for more than one address if they are a few urls. for more address you need to recreate HttpClient for each request.
Kipping HttpHandler alive help you to create connection per address and it won't create more than one connection for same address. DO NOT FORGET TO SET "DisposeHandler" TO FALSE.