ASP.Net Web API with Fiddler and Postman

Description: In this article, we will learn about the concept of ASP.NET Web API using Visual Studio 2015. Also, we will learn to test Web API using Fiddler and Postman Clients.


  • Creating the very basic WebApi project in Visual Studio
  • Create methods to perform CRUD (Create, Read, Update and Delete) operations with WebApi Controller using ADO.NET Entity Framework 6.1.3
  • Learn the way to make your WebApi return data in specific formats like JSON, XML etc.
  • Downloading and installing Fiddler tool and testing the WebApi with it
  • Downloading and installing Postman tool and testing the WebApi with it

ASP.NET Web API is a framework that allow us to build HTTP services over the top of .NET Framework. It is so flexible that it can reach a broad range of clients, including browsers and portable devices. It’s main feature, which makes it unique, is that it is RESTful (Representational State Transfer) i.e. all that data is passed over HTTP and not on SOAP like that of WCF Services.

Unlike SOAP, a WebApi works on pre-defined standards i.e. it has pre-defined verbs, known as HTTP verbs, to work. These verbs are mentioned below:

  1. GET – It is used to fetch the data
  2. PUT – It is used to update the data
  3. POST – It is used to create the data
  4. DELETE – It is used to delete the data

Note: ASP.NET WebApi works on the MVC (Model-View-Controller) architectural pattern, so MVC is a pre-requisite.

Creating a WebApi Project in Visual Studio:

Step 1: Run Visual studio on your machine and click on New Project.

Step 2: The below dialog box appears, click on Web under Visual C# tab –> ASP.NET Web Application –> Give the name of the project –> OK.

Step 3: Select the WebApi option and click on OK.

Step 4: Create the Database and Insert some sample data using the following SQL script.

CREATE TABLE [dbo].[Product] (
    [Id]       INT           IDENTITY (1, 1) NOT NULL,
    [Name]     VARCHAR (100) NOT NULL,
    [Price]    INT           NOT NULL,
    [Category] VARCHAR (100) NOT NULL,
INSERT INTO [dbo].[Product] ([Id], [Name], [Price], [Category]) VALUES (1, N'Mobile', 500, N'Electronics')
INSERT INTO [dbo].[Product] ([Id], [Name], [Price], [Category]) VALUES (2, N'Tablet', 700, N'Electronics')
INSERT INTO [dbo].[Product] ([Id], [Name], [Price], [Category]) VALUES (3, N'Mouse', 200, N'Electronics')
INSERT INTO [dbo].[Product] ([Id], [Name], [Price], [Category]) VALUES (4, N'Keyboard', 340, N'Electronics')
INSERT INTO [dbo].[Product] ([Id], [Name], [Price], [Category]) VALUES (5, N'Speakers', 5000, N'Electronics')
INSERT INTO [dbo].[Product] ([Id], [Name], [Price], [Category]) VALUES (6, N'T-Shirts', 100, N'Wearables')
INSERT INTO [dbo].[Product] ([Id], [Name], [Price], [Category]) VALUES (7, N'Pants', 120, N'Wearables')
INSERT INTO [dbo].[Product] ([Id], [Name], [Price], [Category]) VALUES (8, N'Jeans', 540, N'Wearables')
INSERT INTO [dbo].[Product] ([Id], [Name], [Price], [Category]) VALUES (9, N'Chips', 50, N'Eatables')
INSERT INTO [dbo].[Product] ([Id], [Name], [Price], [Category]) VALUES (10, N'Coke', 30, N'Eatables')

The final table will be like below.

Now we need to do all the CRUD operations on the above table and data.

Step 5: Create a Class Library project that connects to database and provide us with the required classes and properties using ADO.NET Entity framework.

Step 6: After clicking on Finish Button, you will see the below EDMX file showing the data-entity relationship as defined in database.

Now, we are done with the connectivity to Database.

Step 7: Now, we need to add the reference of the above created project in our Web Api project, so follow the below steps.

Step 8: Now we need to create a new ProductsController.cs file in the Controllers folder of WebApi Project. This file will contain the methods that corresponds to HTTP verbs that we discussed in the very begining of this tutorial.

Step 9: Add the following code to the ProductsController.cs.

public ProductEntities Entities = new ProductEntities();
        public HttpResponseMessage Get()
                return Request.CreateResponse(HttpStatusCode.Found, Entities.Products.ToList());
            catch (Exception)
                return Request.CreateErrorResponse(HttpStatusCode.NotFound, "No Data found");
        public HttpResponseMessage Get(int id)
                return Request.CreateResponse(HttpStatusCode.Found, Entities.Products.SingleOrDefault(p => p.Id == id));
            catch (Exception)
                return Request.CreateErrorResponse(HttpStatusCode.NotFound, "No Data found");
        public HttpResponseMessage Post([FromBody] Product product)
                var response = Request.CreateResponse(HttpStatusCode.Created, product);
                response.Headers.Location = Request.RequestUri;
                return response;
            catch (Exception)
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, "Data not inserted");
        public HttpResponseMessage Delete(int id)
                var product = Entities.Products.SingleOrDefault(p => p.Id == id);
                if (product == null)
                    return Request.CreateErrorResponse(HttpStatusCode.BadRequest, "Product not found to delete");
                return Request.CreateResponse(HttpStatusCode.OK, "Product Deleted Successfully");
            catch (Exception)
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, "Product not deleted");
        public HttpResponseMessage Put(int id, [FromBody] Product product)
                var entity = Entities.Products.SingleOrDefault(p => p.Id == id);
                if (entity == null)
                    return Request.CreateErrorResponse(HttpStatusCode.BadRequest, "Product not found ");
                entity.Category = product.Category;
                entity.Name = product.Name;
                entity.Price = product.Price;
                return Request.CreateResponse(HttpStatusCode.OK, "Product Updated Successfully");
            catch (Exception ex)
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ex);

Step 10: Go to App_Start folder of the root directory and open WebApiConfig.cs file and add the following code of lines.

config.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue("application/json"));

The above two lines makes the API, only JSON supported. So, by default, now our API will support only JSON Media type format.

Now, our API is ready. Just add the below connection string to the API’s web.config file.

<add name="ProductEntities"
provider=System.Data.SqlClient;provider connection string="
data source=(local);initial catalog=DemoDB;integrated security=True;MultipleActiveResultSets=True;App=EntityFramework""
providerName="System.Data.EntityClient" />

Press Ctrl + F5 and navigate to http://localhost:26317/api/products. You will see the details of product table in JSON format as below.

Now, as per the Agenda of this article, we will install Fiddler tool and Postman tool to test the API functionality.

Using Fiddler to test Web Api

Step 1: Download the fiddler from the below url and as shown in the screenshot.

Install the downloaded exe file and run it.

Step 2: First we will check the GET functionality. So, follow the steps shown in screenshot below and you will get the result in JSON format.


Step 2: Now we will test POST (Insert) functionality.

Now the data is inserted on 12th row.

Step 3: Now we will update the data on 12th Id using the PUT functionality.

Now, the data is updated successfully.

Step 4: Now we will DELETE the 12th record.

But, using Fiddler to just test the Web Api functionality looks complicated, so instead of using Fiddler, we can use Postman (Google Chrome Extension).

Using Postman to test Web Api

Step 1: Install Postman App in Google Chrome browser as shown below.

Step 2: Run Postman app from the Apps option in Google chrome browser. So, now testing the GET Functionality.

Step 3: Testing the POST functionality.

So, the record is inserted at 13th row.

Step 4: Testing the PUT functionality.

So, data updated in Database.

Step 5: Finally test the Delete functionality.

Conclusion: Personally, I feel using Postman to test Web Api’s and WCF services. We can also use fiddler, but if the API is too complex, so I recommend to use Fiddler as it gives more flexibility to test the services.

Hope you liked the above tutorial. If so, do comment with your compliments and queries. I will try to reply ASAP.


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