Is it possible to use HttpClient (C#) in .NET Core and .NET Framework?

Yes, it is possible to use HttpClient in both .NET Core and .NET Framework. HttpClient is a class in the System.Net.Http namespace that provides a base class for sending HTTP requests and receiving HTTP responses from a resource identified by a URI.

In .NET Framework, HttpClient is available starting from .NET Framework 4.5. In .NET Core, it is available from the initial release of .NET Core 1.0 and is part of the .NET Standard library, which ensures it is consistent across different .NET implementations.

Here's an example of how you can use HttpClient to send an HTTP GET request in both .NET Core and .NET Framework:

using System;
using System.Net.Http;
using System.Threading.Tasks;

class Program
{
    static async Task Main(string[] args)
    {
        using (HttpClient client = new HttpClient())
        {
            try
            {
                // Replace with your desired URI
                string uri = "http://example.com";

                HttpResponseMessage response = await client.GetAsync(uri);
                response.EnsureSuccessStatusCode();

                string responseBody = await response.Content.ReadAsStringAsync();
                Console.WriteLine(responseBody);
            }
            catch (HttpRequestException e)
            {
                Console.WriteLine("\nException Caught!");
                Console.WriteLine("Message :{0} ", e.Message);
            }
        }
    }
}

To use HttpClient in your C# project, you may need to install the System.Net.Http package, especially if you are working with older versions of .NET Framework. For .NET Core projects, HttpClient is included by default.

To install System.Net.Http in a .NET Framework project, you can use the following NuGet package manager console command:

Install-Package System.Net.Http

Or you can add the package reference directly to your project file:

<ItemGroup>
  <PackageReference Include="System.Net.Http" Version="4.3.4" />
</ItemGroup>

Make sure to replace 4.3.4 with the latest version or the version that is compatible with your project.

In .NET Core projects, you typically do not need to install the System.Net.Http package separately, as it is included by default. However, if you need to update it or ensure a specific version is used, you can similarly use the NuGet package manager console or edit the project file directly.

Note that there are some differences in how HttpClient behaves and is optimized in .NET Core compared to the .NET Framework. For example, .NET Core has improved DNS refreshing, sockets handling, and better support for asynchronous operations. It is generally recommended to use the latest version of .NET Core for the best performance and security features.