I'm attempting to call my ASP.NET Core API using HttpClient. The .NET Core server is running on my PC, so I'm trying to send the request to localhost. I added a try-catch block to catch the inner exception, but it's not providing enough information for me to understand the problem. I'm receiving the following error message: "System.Net.Http.HttpRequestException: An error occurred while sending the request. ---> System.IO.IOException: The response ended prematurely." 
Below is my code 
using System;
using System.Net.Http;
using System.Threading.Tasks;

class Program
{
    static async Task Main(string[] args)
    {
        // Create an instance of HttpClient
        using (HttpClient client = new HttpClient())
        {
            // Define the URL to which the POST request will be sent
            string url = "http://192.168.1.105:238/register";

            // Define user information to be sent in the POST request
            var userData = new
            {
                username = "ashokpatel983",
                email = "[email protected]",
                password = "ashok33123"
            };

            // Convert user information to JSON format
            string jsonData = Newtonsoft.Json.JsonConvert.SerializeObject(userData);

            // Define the content to be sent in the POST request
            HttpContent content = new StringContent(jsonData, System.Text.Encoding.UTF8, "application/json");

            // Send the POST request and await the response
            HttpResponseMessage response = await client.PostAsync(url, content);

            // Check if the request was successful (status code 200)
            if (response.IsSuccessStatusCode)
            {
                // Read and display the response content
                string responseBody = await response.Content.ReadAsStringAsync();
                Console.WriteLine("Registration successful. Response: " + responseBody);
            }
            else
            {
                Console.WriteLine("Error: " + response.StatusCode);
            }
        }
    }
}

Here I define user information (username, email, password) as an anonymous object and then serialize the user information object to JSON format using Newtonsoft.Json.JsonConvert.SerializeObject method and the content to be sent in the POST request as JSON data.
And then sending the POST request to the server with the user information in the request body.
If the registration is successful (status code 200), we display the response content. Otherwise, we handle the error accordingly.

If you're also facing this issue and this question comes to mind, you've come to the right place. In this post, we will discuss possible solutions for that error.

Solution for "The response ended prematurely" error when using HttpClient in C#

 "The response ended prematurely" error while using HttpClient in C#, it typically indicates that the HTTP response from the server was incomplete or not fully received. This can happen due to various reasons, such as network issues, server-side problems, or incorrect usage of HttpClient. 

  1. Ensure proper disposal of HttpClient instances:

    One common cause of this error is not properly disposing of HttpClient instances. We should always ensure that HttpClient instances are properly disposed of after use, preferably by wrapping them in a using statement. This ensures that underlying resources are released correctly and prevents potential issues like connection leaks. 

    
using (HttpClient client = new HttpClient())
{
    // Use HttpClient to send requests
}

  2. Check for network or server issues:

    Sometimes, this error can occur due to network instability or issues on the server side. We should verify that our network connection is stable and that the server we are communicating with is functioning properly. It's also a good idea to check if other HTTP clients (e.g., web browsers) can successfully access the same endpoint.

  3. Review HttpClient configuration:

    We should review our HttpClient configuration to ensure that it's set up correctly for our requirements. This includes settings such as timeout values, maximum connections per server, and handling of redirects. Adjusting these settings appropriately based on our specific use case may help mitigate the "response ended prematurely" error.

  4. Consider asynchronous programming:

    If we are making synchronous HTTP requests with HttpClient, consider switching to asynchronous programming using async/await. Asynchronous operations can better handle situations where responses take longer to complete or encounter network delays. 

    
public async Task<HttpResponseMessage> GetResponseAsync(string url)
{
    using (HttpClient client = new HttpClient())
    {
        return await client.GetAsync(url);
    }
}

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