Friday, March 23, 2018

Overhead of Creating a new HttpClient per call/request - Exception : Unable to connect to the remote server System.Net.Sockets.SocketException: Only one usage of each socket address (protocol/network address/port) is normally permitted.

Exception : Unable to connect to the remote server System.Net.Sockets.SocketException: Only one usage of each socket address (protocol/network address/port) is normally permitted.

“As Per Microsoft documentation, HTTP Client is intended to be instantiated once and it should be reused thought the life of application.”

Let evaluate the above Microsoft document statement about HttpClient, if you are creating a new HttpClient instance it means one TCP/IP connection is established with Server

using System.Net.Http;
HttpClient client = new HttpClient();

Creating a new HTTPClient instance per request, it can exhaust the available TCP socket and server comes under heavy load.

There is limited number for connection pool on Windows Server, if you have already used available connection or exhaust the connection pool then you encountered error:

Unable to connect to the remote server
System.Net.Sockets.SocketException: Only one usage of each socket address (protocol/network address/port) is normally permitted.

Disposing HttpClient instance by Using Statement:
Using Statement in C# is used for Disposable object and, if object goes out of using scope, it is disposed.

HttpClient is also disposable object and if we use using statement to instantiate HttpClient and when it goes out of scope, it is being disposed.

using (HttpClient client = new HttpClient())


In Disposing of HttpClient it close the active TCP/IP connection with Server but due to delay on the network there is always waiting time from other side and If you create more HttpClient instances it means you opened more TCP/IP connections, it could be very costly and more waiting time process to dispose HttpClient instance.

Conclusion is that for creating HttpClient instance per request by using “using” statement it could be more problematic.

It is advisable to use the single instance of HttpClient per Web Service throughout application. You can manage the single instance of HTTPClient by using the singleton Patterns or static class.

public sealed class CommonHttpClient
        private static HttpClient instance;

        private static object syncRoot = new object();

        public static HttpClient Instance
                if (instance == null)
                    lock (syncRoot)
                        if (instance == null)
                            var handler = new HttpClientHandler { UseDefaultCredentials                                        = true, Credentials = CredentialCache.DefaultCredentials };
                            var client = new HttpClient(handler, false)
                                             BaseAddress = newUri(“http://localhost”)
                            instance = client;

                return instance;


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Friday, March 16, 2018

Import Swagger APIs documentation into Postman

Swagger lovers can easily import APIs documentation information into Postman and Postman provides ability to import API information from Swagger directly.

below are steps :
  • Create New Collection : 
  •     Click on Import button on top panel , Import Popup will be opened

                                                                     (Import Window)

now you can see list of imported API requests

Monday, March 12, 2018

The Lifecycle of an ASP.NET Web API

In this blog, we will discuss the life cycle of an ASP.NET Web API message, which travels from Server to client.

ASP.NET Web API is a .net framework which is used to build HTTP based Restful service and Web API is a lightweight service and supports broad range of clients (mobile app, web apps etc.) and it allows multiple devices to access data via API with any configuration settings.

Steps To Create ASP.NET Web API

Web API Request/Repose Processing Pipeline:

Life-cycle of WEB API

Http Server:  Gets request from host (IIS or Managed application).

Message Handler/Delegating Handler:  it is used before routing the request and these message handler arranged module in HTTP pipeline and each receives request and does some work and pass to next message handler in pipeline. Message handler can send response back without passing to next handler and you can use Message Handler to validate request and based on this, create response also.

Routing Dispatcher: Parse route information and depending on route dispatch request.

Controller Dispatcher : it creates instance of Web API Controller based on matched route

Authorization Filter: after controller instantiate, request pass through the authorization filters, if authorization filter configured in pipeline and it checks authorization of request, in case of fail, send back response directly.

Model Binding: controller calls web API Controller method, before that it set method parameters value, this is called model binding. We can defined own custom model binding to set action parameter value ( web api parameter binding)

Action Filter: After Model Binding, if action is attributed with action filter, action filter will be invoked and it is invoked two times, One before action is executed and 2nd time, after action executed

Controller Action: controller action execute its code and on depend of result, it created HTTP Response.

Exception Handler: if any unhand-led exception is occurred, exception filer is execute, it can have common exception handling logic.

Tuesday, March 6, 2018

How to add Authorization Header (Custom Header) in Swagger UI

In this blog, we are going to discuss how to add custom header parameter (authorization header) in Swagger UI for ASP.Net web API.

We use request header (like authentication) to pass client information to web API but in Swagger UI, there is no any simple or straight way to add custom header parameter.
To add customer header parameter in Swagger UI, we need to implement IOperationFilter interface

internal class AuthorizationHeaderParameterOperationFilter : IOperationFilter
        public void Apply(Operation operation, SchemaRegistry schemaRegistry, ApiDescription apiDescription)
            if (operation.parameters == null)
                operation.parameters = new List<Parameter>();

     operation.parameters.Add(new Parameter
                name = "X-API-Token",
                @in = "header",
                description = "access token",
                required = true,
                type = "string"

SwaggerConfig .cs :

public static void Register()
            var thisAssembly = typeof(SwaggerConfig).Assembly;
                .EnableSwagger(c =>
                .EnableSwaggerUi(c => { });

As below you can see, X-API-token as additional parameter for your Web API to take authorization token and pass to web API for user authentication 

Swagger UI Add Authorization Header (Custom Header)
Swagger UI Add Authorization Header (Custom Header)

Other swagger related posts:
·         Disable Swagger UI

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SQL Server - Identify unused indexes

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