REST - HttpClient - Server, C#, Practical example

Question

REST - HttpClient - Server, C#, Practical example

Markus Freitag 3,791

Hello,

The idea would be to send a JSON response on GET and on POST.

With GET I query all entries. With PUT I add entries.

Both return a response in JSON.

Sounds simple, who has experience certainly easy to solve. Can someone show me?

// Response for Get and Put
public class ResponseStandard
{
	[JsonProperty("status")]
	public int Status { get; set; }

	[JsonProperty("error")]
	public int Error { get; set; }

	[JsonProperty("msg")]
	public string Msg { get; set; }
}

// Process 
public class Product
{
	[JsonProperty("name")]
	public string Name { get; set; }

	[JsonProperty("price")]
	public double Price { get; set; }

	[JsonProperty("quantity")]
	public int Quantity { get; set; }
}

// My working object.
  List<Product> ListProduct = new List<Product>();

// ** On Client desktop C# App
   Add, Delete, Edit is important

Can I transfer the application to another PC and test it, without a development environment? If so, what would I need to do? Do you have an instruction?

AgaveJoe 1,510 Reputation points

2023-09-08T17:58:16.5066667+00:00

Can I transfer the application to another PC and test it, without a development environment?

The target machine needs a host like IIS to host Web API.

Configuring Step 1: Install IIS and ASP.NET Modules

If so, what would I need to do?

You need to learn IIS, networking, and maybe how to configure a firewall.

Create a Web Site

We have no idea how your network is setup so we can't provide much information. Assuming it is possible to get to this "PC" over the network then you'll just use the PC's IP address in the URL. But, most likely there's configuration you need to do which is unknown at this time.
Johan Smarius 470 Reputation points MVP

2023-09-09T17:41:34.4633333+00:00

On which version of the framework should this work?

If I look at your example code, there are some strange things. You can return information from an API, but if this must be a webapi, the HTTP status code will always be returned. You can return the List of products in the body of the response. So there is no need to make a custom class for this.

You talk about Get, Put and Post. For put you mention that a resource should be added. If you follow the HTTP guidelines, the put operation is only for modification. The post operation is for adding resources.

Without knowing how your server code is implemented, it is hard to help you with the code for the client. Can you give some more information on the server implementation?
Markus Freitag 3,791 Reputation points

2023-09-10T15:18:36.6233333+00:00

On which version of the framework should this work?

.NET4.7.2

Please see here too https://learn.microsoft.com/en-us/answers/questions/1359331/httpclient-rest-interface-get-post?page=1&orderby=helpful&comment=answer-1310786

I need to develop a C# desktop application. I receive the data from the customer via REST interface. I don't get a MockServer. I also have no experience with REST. So everything is difficult.

I ask you to support me. Thank you very much.
Lan Huang-MSFT 30,206 Reputation points Microsoft External Staff

2023-09-11T06:31:39.43+00:00

Hi @Markus Freitag,

I've given you an example on WebAPI.

Where are you currently having problems, is it WinForm or WebAPI?

Enabling CRUD Operations in ASP.NET Web API
Markus Freitag 3,791 Reputation points

2023-09-11T15:21:22.7233333+00:00

I've given you an example on WebAPI.

Yes, thanks, connection is ok, I can't send the request.

I started the server first. I see it with Edge. Then in a second application the client. There is an error sending. There is no connection error, there should be a connection.
AgaveJoe 1,510 Reputation points

2023-09-11T17:30:30.5366667+00:00

There is an error sending. There is no connection error, there should be a connection.

What is the error? Is there anyway you can provide the code?
SurferOnWww 4,951 Reputation points

2023-09-12T01:32:31.6+00:00

I suggest that you use the Fiddler or equivalent to see what's going on between the client and server.

Markus Freitag 3,791

What is the error? Is there anyway you can provide the code?

Hello,

nothing works. I have checked all the recommendations.

https://stackoverflow.com/questions/54089849/httpclient-getasync-the-underlying-connection-was-closed-an-unexpected-error-o

Do you have another tip for me, please? Here my code. WinFoms App C#

using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;

using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WebClientREST
{
public partial class Form1 : Form
{
	public Form1()
	{
		//System.Net.ServicePointManager.SecurityProtocol |=
		//           SecurityProtocolType.Tls13 |
		//           SecurityProtocolType.Tls12 |
		//           SecurityProtocolType.Tls11 |
		//           SecurityProtocolType.Tls;

		InitializeComponent();           
	}     

	public class ResponseStandard
	{
		[JsonProperty("status")]
		public int Status { get; set; }

		[JsonProperty("error")]
		public int Error { get; set; }

		[JsonProperty("msg")]
		public string Msg { get; set; }
	}

	private async void btnTestREST_Click(object sender, EventArgs e)
	{
		ResponseStandard p = new ResponseStandard()
		{
			Status = 4,
			Error = 4,
			Msg = "F",
		};

		try
		{
			System.Net.ServicePointManager.SecurityProtocol |=
				   SecurityProtocolType.Tls13 |
				   SecurityProtocolType.Tls12 |
				   SecurityProtocolType.Tls11 |
				   SecurityProtocolType.Tls;

			using (var client = new HttpClient())
			{
				client.BaseAddress = new Uri("https://localhost:55892/");

				client.DefaultRequestHeaders.Accept.Clear();
				client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
				string authorization = $"{""}:{""}";
				client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", "");

			   

				//GET Method
				HttpResponseMessage response = await client.GetAsync("api/valuesGET");
				if (response.IsSuccessStatusCode)
				{
					List<ResponseStandard> requestWorkorder = null;
					requestWorkorder = await response.Content.ReadAsAsync<List<ResponseStandard>>();
					Console.WriteLine("Id:{0}\tName:{1}", requestWorkorder[0].Status, requestWorkorder[0].Error);

				}
				//POST Method
				HttpResponseMessage response1 = await client.PostAsJsonAsync("api/valuesPOST", p);

				if (response1.IsSuccessStatusCode)
				{
					Console.WriteLine("Success");
				}
				else
				{
					Console.WriteLine("Internal server Error");
				}
			}
		}
		catch (HttpRequestException eww)
		{
			MessageBox.Show(eww.InnerException.Message);

			MessageBox.Show(eww.Message);
		}
		catch (Exception ex)
		{
			MessageBox.Show(ex.Message);
		}
	}
}

enter image description here

Server
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;

namespace WebRESTServer.Controllers
{
    public class ResponseStandard
    {
        [JsonProperty("status")]
        public int Status { get; set; }

        [JsonProperty("error")]
        public int Error { get; set; }

        [JsonProperty("msg")]
        public string Msg { get; set; }
    }


    public class Product
    {
        [JsonProperty("name")]
        public string Name { get; set; }

        [JsonProperty("price")]
        public double Price { get; set; }

        [JsonProperty("quantity")]
        public int Quantity { get; set; }
    }


    public class ValuesGETController : ApiController
    {
        List<Product> ListProduct = new List<Product>();

        ResponseStandard[] requestWorkorders = new ResponseStandard[]
        {
     new ResponseStandard { Status = 1,  Error = 1, Msg="a" },
     new ResponseStandard{Status = 2, Error=2,Msg= "b" },
     new  ResponseStandard{ Status = 3, Error=3,Msg= "c" }
        };
        public IEnumerable<ResponseStandard> GetAllProducts()
        {
            return requestWorkorders;
        }

        public IHttpActionResult GetProduct(int status)
        {
            var product = requestWorkorders.FirstOrDefault((p) => p.Status == status);
            if (product == null)
            {
                return NotFound();
            }
            return Ok(product);
        }
    }
    public class ValuesPOSTController : ApiController
    {
        public IHttpActionResult Post([FromBody] ResponseStandard requestWorkorder)
        {
            List<ResponseStandard> requestWorkorders = new List<ResponseStandard>();
            requestWorkorders.Add(requestWorkorder);
            return Ok();
        }

    }
}

enter image description here

Lan Huang-MSFT 30,206 Reputation points Microsoft External Staff

2023-09-14T01:58:23.79+00:00

Hi @Markus Freitag,

You'd better provide English error message and ex internal information, similar to:

Please make sure the server is always running, run the WebAPI first and then the client. Don't stop running WebAPI while running the client.

Markus Freitag 3,791

Hello,

The exception. The underlying connection has been closed: Unexpected error while sending

   ServicePointManager.SecurityProtocol |=
                          SecurityProtocolType.Tls13 |
                          SecurityProtocolType.Tls12 |
                          SecurityProtocolType.Tls11 |
                          SecurityProtocolType.Tls |
                          SecurityProtocolType.Ssl3;

I set this. The same.
Server is running from my point of view!

ssl,tls, certificate

Certificate. I don't know what the cause could be.


----0
Die zugrunde liegende Verbindung wurde geschlossen: Unerwarteter Fehler beim Senden. / means    The underlying connection was closed: An unexpected error occurred on a send. 
----A
Fehler beim Senden der Anforderung.  / means   Error sending the request.
----B
   bei System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
   bei System.Net.Http.HttpClientHandler.GetResponseCallback(IAsyncResult ar)

enter image description here

Lan Huang-MSFT 30,206 Reputation points Microsoft External Staff

2023-09-15T09:53:30.4966667+00:00

Hi @Markus Freitag,

If you remove the code about SSL, do you get the same error message?

Based on your previous description, you are using 4.7.2. .NET 4.6 and later does not require any additional work to support TLS 1.2 and is supported by default.

Sorry, I can't reproduce your issue. Maybe you could follow SurferOnWww's advice: use Fiddler or equivalent to see what's going on between client and server.
Markus Freitag 3,791 Reputation points

2023-09-15T10:37:02.1733333+00:00

If you remove the code about SSL, do you get the same error message?

Yes the same error. I use 4.7.2 and 4.8, the same
Markus Freitag 3,791 Reputation points

2023-09-17T18:46:45.5566667+00:00

Sorry, I can't reproduce your issue. Maybe you could follow SurferOnWww's advice: use Fiddler or equivalent to see what's going on between client and server.

That's a shame, I don't have any experience with Fiddler either. Let's see what I do. All complicated. Maybe it's a matter of company security. Thanks for your help.

Your answer

AgaveJoe 1,510 Reputation points

2023-09-08T17:58:16.5066667+00:00

Can I transfer the application to another PC and test it, without a development environment?

The target machine needs a host like IIS to host Web API.

Configuring Step 1: Install IIS and ASP.NET Modules

If so, what would I need to do?

You need to learn IIS, networking, and maybe how to configure a firewall.

Create a Web Site

We have no idea how your network is setup so we can't provide much information. Assuming it is possible to get to this "PC" over the network then you'll just use the PC's IP address in the URL. But, most likely there's configuration you need to do which is unknown at this time.
Johan Smarius 470 Reputation points MVP

2023-09-09T17:41:34.4633333+00:00

On which version of the framework should this work?

If I look at your example code, there are some strange things. You can return information from an API, but if this must be a webapi, the HTTP status code will always be returned. You can return the List of products in the body of the response. So there is no need to make a custom class for this.

You talk about Get, Put and Post. For put you mention that a resource should be added. If you follow the HTTP guidelines, the put operation is only for modification. The post operation is for adding resources.

Without knowing how your server code is implemented, it is hard to help you with the code for the client. Can you give some more information on the server implementation?
Markus Freitag 3,791 Reputation points

2023-09-10T15:18:36.6233333+00:00

On which version of the framework should this work?

.NET4.7.2

Please see here too https://learn.microsoft.com/en-us/answers/questions/1359331/httpclient-rest-interface-get-post?page=1&orderby=helpful&comment=answer-1310786

I need to develop a C# desktop application. I receive the data from the customer via REST interface. I don't get a MockServer. I also have no experience with REST. So everything is difficult.

I ask you to support me. Thank you very much.
Lan Huang-MSFT 30,206 Reputation points Microsoft External Staff

2023-09-11T06:31:39.43+00:00

Hi @Markus Freitag,

I've given you an example on WebAPI.

Where are you currently having problems, is it WinForm or WebAPI?

Enabling CRUD Operations in ASP.NET Web API
Markus Freitag 3,791 Reputation points

2023-09-11T15:21:22.7233333+00:00

I've given you an example on WebAPI.

Yes, thanks, connection is ok, I can't send the request.

I started the server first. I see it with Edge. Then in a second application the client. There is an error sending. There is no connection error, there should be a connection.
AgaveJoe 1,510 Reputation points

2023-09-11T17:30:30.5366667+00:00

There is an error sending. There is no connection error, there should be a connection.

What is the error? Is there anyway you can provide the code?
SurferOnWww 4,951 Reputation points

2023-09-12T01:32:31.6+00:00

I suggest that you use the Fiddler or equivalent to see what's going on between the client and server.
Lan Huang-MSFT 30,206 Reputation points Microsoft External Staff

2023-09-14T01:58:23.79+00:00

Hi @Markus Freitag,

You'd better provide English error message and ex internal information, similar to:

Please make sure the server is always running, run the WebAPI first and then the client. Don't stop running WebAPI while running the client.
Markus Freitag 3,791 Reputation points

2023-09-14T17:09:55.03+00:00

Hello,

The exception. The underlying connection has been closed: Unexpected error while sending

ServicePointManager.SecurityProtocol |= SecurityProtocolType.Tls13 | SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls | SecurityProtocolType.Ssl3; I set this. The same. Server is running from my point of view! ssl,tls, certificate Certificate. I don't know what the cause could be. ----0 Die zugrunde liegende Verbindung wurde geschlossen: Unerwarteter Fehler beim Senden. / means The underlying connection was closed: An unexpected error occurred on a send. ----A Fehler beim Senden der Anforderung. / means Error sending the request. ----B bei System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult) bei System.Net.Http.HttpClientHandler.GetResponseCallback(IAsyncResult ar)
Lan Huang-MSFT 30,206 Reputation points Microsoft External Staff

2023-09-15T09:53:30.4966667+00:00

Hi @Markus Freitag,

If you remove the code about SSL, do you get the same error message?

Based on your previous description, you are using 4.7.2. .NET 4.6 and later does not require any additional work to support TLS 1.2 and is supported by default.

Sorry, I can't reproduce your issue. Maybe you could follow SurferOnWww's advice: use Fiddler or equivalent to see what's going on between client and server.
Markus Freitag 3,791 Reputation points

2023-09-15T10:37:02.1733333+00:00

If you remove the code about SSL, do you get the same error message?

Yes the same error. I use 4.7.2 and 4.8, the same
Markus Freitag 3,791 Reputation points

2023-09-17T18:46:45.5566667+00:00

Sorry, I can't reproduce your issue. Maybe you could follow SurferOnWww's advice: use Fiddler or equivalent to see what's going on between client and server.

That's a shame, I don't have any experience with Fiddler either. Let's see what I do. All complicated. Maybe it's a matter of company security. Thanks for your help.

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REST - HttpClient - Server, C#, Practical example

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