Using Entity Framework with ASP.NET Web API 2 to build RESTful applications

ASP.NET Web API 2 is a framework for building RESTful applications on the .NET Framework. A broad range of clients, including browsers and mobile devices, can be built to process and present the data through HTTP web services.

In this post, I will build a basic web service by using ASP.NET Web API 2 template, reversed engineer the data model from existing database table by using Entity Framework 6, and finally scaffold and code the web service controller.

ASP.NET Web API template

Create a new project EmployeeWebAPI2 by using C# ASP.NET Application and Web API template in Microsoft Visual Studio 2013.

Reversed Engineering Model From Database

Here is the database schema in Microsoft SQL Server T-SQL.

Right Click on the project in Solution Explorer, and choose ‘Entity Framework – Reversed Engineering Code First’. Then connect to the instance (local) and database (test), and generate the model from test database for table ‘HR.Employees’. For more detail, please refer to my another post.

It will create testContext.cs, Employee.cs and EmployeeMap.cs. I commented out the key and relationship self reference to simply the object class.

Build Web Service Controller

Right Click on Controllers folder, and choose ‘Add->New Scaffold Item”. Choose ‘Web API 2 Controller with read/write Access’. Type ‘EmployeeController’ as controller name.

It will generate a EmployeeController.cs with a list of GET, POST, PUT and DELETE methods. The following steps show how to complete the various web URI methods using EF 6.

1. use the model generated from EF 6.

using EmployeeWebAPI2.Models;

2. GET api/employee

        // GET api/employee
        public IEnumerable<Employee> Get()
        {
            using (testContext entities = new testContext())
            {
                return entities.Employees.ToList<Employee>();
            }
        }

3. GET api/employee/5

        // GET api/employee/5
        public Employee Get(int id)
        {
            using (testContext entities = new testContext())
            {
                return entities.Employees.SingleOrDefault<Employee>(b => b.empid == id);
            }
        }

4. POST api/employee

        // POST api/employee
        public HttpResponseMessage Post(Employee value)
        {
            try
            {
                if (ModelState.IsValid)
                {
                    using (testContext entities = new testContext())
                    {
                        entities.Employees.Add(value);
                        entities.SaveChanges();
                        return Request.CreateResponse(HttpStatusCode.OK);
                    }
                }
                else
                {
                    return Request.CreateResponse(HttpStatusCode.InternalServerError, "invalid New Value");
                }
            }
            catch (Exception ex)
            {
                return Request.CreateResponse(HttpStatusCode.InternalServerError, ex.Message);
            }
        }

5. PUT api/employee/5

        // PUT api/employee/5
        public HttpResponseMessage Put(int id, Employee value)
        {
            try
            {
                using (testContext entities = new testContext())
                {
                    Employee myEmp = entities.Employees.SingleOrDefault<Employee>(b => b.empid == id);
                    // update all the fields
                    myEmp.empid = value.empid;
                    myEmp.lastname = value.lastname;
                    myEmp.firstname = value.firstname;
                    myEmp.title = value.title;
                    myEmp.titleofcourtesy = value.titleofcourtesy;
                    myEmp.birthdate = value.birthdate;
                    myEmp.hiredate = value.hiredate;
                    myEmp.address = value.address;
                    myEmp.city = value.city;
                    myEmp.region = value.region;
                    myEmp.postalcode = value.postalcode;
                    myEmp.country = value.country;
                    myEmp.phone = value.phone;
                    myEmp.mgrid = value.mgrid;
                    // flush to disk
                    entities.SaveChanges();
                    return Request.CreateResponse(HttpStatusCode.OK);
                }
            }
            catch (Exception ex)
            {
                return Request.CreateResponse(HttpStatusCode.InternalServerError, ex.Message);
            }
        }

6. DELETE api/employee/5

        // DELETE api/employee/5
        public HttpResponseMessage Delete(int id)
        {
            try
            {
                using (testContext entities = new testContext())
                {
                    Employee myEmp = entities.Employees.SingleOrDefault<Employee>(b => b.empid == id);
                    entities.Employees.Remove(myEmp);
                    entities.SaveChanges();
                    return Request.CreateResponse(HttpStatusCode.OK);
                }
            }
            catch (Exception ex)
            {
                return Request.CreateResponse(HttpStatusCode.InternalServerError, ex.Message);
            }
        }

Here is the complete code for EmployeeController.cs.

Test the web service

Build the solution and run the web service. Point your localhost url to:
http://localhost:55142/api/employee/2

It will get the following JSON object from url for (empid=2):


{"empid":2,"lastname":"Funk","firstname":"Don","title":"Vice President, Sales","titleofcourtesy":"Dr.","birthdate":"1962-02-19T00:00:00","hiredate":"2002-08-14T00:00:00","address":"9012 W. Capital Way","city":"Tacoma","region":"WA","postalcode":"10001","country":"USA","phone":"(206) 555-0100","mgrid":1}

I also use a tool called ‘Fiddler Web Debugger’ to examine the JSON / XML response return from the web service.

In the next post, I will write a client application to consume all the URIs in the above web api services.

About henry416
I am a computer technology explorer and an university student based on Toronto. If you have any question, please feel free to discuss and comment here

One Response to Using Entity Framework with ASP.NET Web API 2 to build RESTful applications

  1. Brad Gilbert says:

    For your put you can actually just do db.Entry(myEmp).CurrentValues.SetValues(newEmp)

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