How Can I Make Secure HTTPS Calls with HttpClient in C#?

Use HttpClient to make HTTPS calls

In C#, the HttpClient class is a powerful tool for making Web API calls. It provides a simple and efficient way to send and receive data, so it is very popular among developers. However, using HttpClient to make HTTPS calls sometimes presents challenges.

Enable HTTPS calls

To enable HTTPS calls using HttpClient, you must first resolve the SSL/TLS trust relationship issue. By default, HttpClient only trusts certificates that are preinstalled in the operating system's certificate store. If the server certificate is not in the store, you will encounter an error saying that the trust relationship cannot be established.

To overcome this problem, you can add the following lines of code to your program:

<code>System.Net.ServicePointManager.SecurityProtocol |= SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls;</code>

This code indicates that HttpClient supports TLS versions 1.2, 1.1 and 1.0. If the server supports a higher version of TLS, such as TLS 1.3, this code may need to be updated accordingly.

Provide certificate and key

In some cases, the server may require the client to provide a certificate and public/private key for authentication. To provide these credentials using HttpClient, you can use the HttpClientHandler class. An example is as follows:

<code>var httpClientHandler = new HttpClientHandler();
httpClientHandler.ClientCertificates.Add(new X509Certificate2(...));</code>

In this code, ... represents the path to the certificate file and, if necessary, the password. HttpClient can then be instantiated using a custom HttpClientHandler:

<code>HttpClient httpClient = new HttpClient(httpClientHandler);</code>

By incorporating these enhancements into your HttpClient code, you can efficiently make secure HTTPS calls and implement trust and authentication mechanisms.

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