Http Client in Visual Basic .NET

Here’s an idiomatic Visual Basic .NET example demonstrating an HTTP client, similar to the concept shown in the provided Go code:

Imports System
Imports System.Net.Http
Imports System.IO

Module HttpClientExample
    Async Function Main() As Task
        ' Create an instance of HttpClient
        Using client As New HttpClient()
            Try
                ' Send an HTTP GET request to a server
                Dim response As HttpResponseMessage = Await client.GetAsync("https://example.com")

                ' Ensure the request was successful
                response.EnsureSuccessStatusCode()

                ' Print the HTTP response status
                Console.WriteLine($"Response status: {CInt(response.StatusCode)} {response.StatusCode}")

                ' Read the response content as a string
                Dim content As String = Await response.Content.ReadAsStringAsync()

                ' Print the first 5 lines of the response body
                Using reader As New StringReader(content)
                    For i As Integer = 0 To 4
                        Dim line As String = reader.ReadLine()
                        If line Is Nothing Then Exit For
                        Console.WriteLine(line)
                    Next
                End Using
            Catch ex As HttpRequestException
                Console.WriteLine($"Error: {ex.Message}")
            End Try
        End Using
    End Function
End Module

This Visual Basic .NET example demonstrates how to use the HttpClient class to make HTTP requests. Here’s a breakdown of the code:

1. We import necessary namespaces: System for basic functionality, System.Net.Http for HTTP client operations, and System.IO for string reading.

2. The Main function is marked as Async to allow the use of asynchronous operations.

3. We create an instance of HttpClient inside a Using block to ensure proper resource disposal.

4. The GetAsync method is used to send an HTTP GET request to “https://example.com”. This is equivalent to the http.Get function in the Go example.

5. We use EnsureSuccessStatusCode to throw an exception if the response status code doesn’t indicate success.

6. The response status is printed to the console.

7. We read the entire response content as a string using ReadAsStringAsync.

8. A StringReader is used to read the first 5 lines of the response content, which are then printed to the console.

9. Exception handling is implemented to catch and display any HTTP request errors.

To run this program:

1. Save the code in a file with a .vb extension (e.g., HttpClientExample.vb).
2. Open a command prompt and navigate to the directory containing the file.
3. Compile the code using the Visual Basic compiler:

vbc HttpClientExample.vb

4. Run the compiled executable:

HttpClientExample.exe

This example showcases Visual Basic .NET’s asynchronous programming capabilities and its built-in HTTP client functionality, which are commonly used for making web requests in .NET applications.