Part 15 - Updatemodel function in mvc

Suggested Videos 
Part 12 - Creating a view to insert data
Part 13 - FormCollection in mvc
Part 14 - Mapping asp.net request data to controller action simple parameter types

In this video we will dsicuss using UpdateModel() function. Please watch Part 14, before proceeding. 



Change the implementation of "Create" action method that is decorated with [HTTPPost] aatribute in "EmployeeController" as shown below.
[HttpPost]
public ActionResult Create(Employee employee)
{
    if (ModelState.IsValid)
    {
        EmployeeBusinessLayer employeeBusinessLayer =
            new EmployeeBusinessLayer();

        employeeBusinessLayer.AddEmmployee(employee);
        return RedirectToAction("Index");
    }
    return View();
}



Please note:
1. Model state is being checked using IsValid boolean property of ModelState object. We will discuss ModelState in a later video session.
2. Instead of passing the individual properties of "Employee" object as parameters to the "Create" action method, we are now passing the "Employee" object itself.
3. The "Employee" object is then handed over to AddEmployee() method of "EmployeeBusinessLayer" class, which takes the responsibility of saving the "Employee" object to the database table.
4. Upon saving the employee, the user is then redirected to the "Index" action method.
5. If there are any "Model" validation errors, ModelState.IsValid returns false. In this case, we stay on the same create view, which gives the opportunity to correct the errors and resubmit the page.

The above method can be rewritten as shown below.
[HttpPost]
public ActionResult Create()
{
    if (ModelState.IsValid)
    {
        EmployeeBusinessLayer employeeBusinessLayer =
            new EmployeeBusinessLayer();

        Employee employee = new Employee();
        UpdateModel<Employee>(employee);

        employeeBusinessLayer.AddEmmployee(employee);
        return RedirectToAction("Index");
    }
    return View();
}

When you make this change, you get a compilation error stating - Type 'MVCDemo.Controllers.EmployeeController' already defines a member called 'Create' with the same parameter types.Our intention here is to overload the "Create" controller action method based on "HttpGet" and "HttpPost". To fix this error, use "ActionName" attribute as shown below.
[HttpGet]
[ActionName("Create")]
public ActionResult Create_Get()
{
    return View();
}

[HttpPost]
[ActionName("Create")]
public ActionResult Create_Post()
{
    if (ModelState.IsValid)
    {
        EmployeeBusinessLayer employeeBusinessLayer =
            new EmployeeBusinessLayer();

        Employee employee = new Employee();
        UpdateModel<Employee>(employee);

        employeeBusinessLayer.AddEmmployee(employee);
        return RedirectToAction("Index");
    }
    return View();
}

Please Note:
1. We have changed the names of "Create" action methods to "Create_Get" and "Create_Post" depending on the actions they respond to.
2. "ActionName" is specified as "Create" for both of these methods. So, if a "GET" request is made to the "URL - http://localhost/MVCDemo/Employee/Create" then "Create_Get()" controller action method is invoked. On the other hand if a "POST" request is made to the same URL, then "Create_Post()" controller action method is invoked.
3. Instead of passing "Employee" object as a parameter to "Create_Post()" action method, we are creating an instance of an "Employee" object with in the function, and updating it using "UpdateModel()" function. "UpdateModel()" function inspects all the HttpRequest inputs such as posted Form data, QueryString, Cookies and Server variables and populate the employee object.

When you run the application, you may get an intermittent error stating - Adding the specified count to the semaphore would cause it to exceed its maximum count. To fix this error, either 
1. Restart IIS 
OR
2. Disable connection pooling in the connection string of your web.config file