Step By Step How to use the TextBox HTML Helper in an MVC 4 View

        By Carmel Schvartzman

In this tutorial we'll learn how to use the most common HTML Helper, the TextBox control, in an MVC View in ASP.NET MVC 4. An MVC View is the responsible for rendering the html for the UI with the user: it is the Presentation level in the ModelViewController software pattern; if so , it is absolutely forbidden to include in it any bussiness logic (wich is holded into the MVC Model) or any application logic (coded inside the MVC Controllers), nor any data fetching(MVC Model responsability, sent via the Controllers).

By convention, the Views are stored inside subfolders of the View folder, named after the corresponding Controllers: then for instance, all the Views you create related to the AccountController will be placed inside the "Account" folder ("Views/Account"). The MVC framework will search a required View to be rendered, in the folder with the name of the Controller, and if it is not there, will search at the "Shared" subfolder. If you want a View to be shared among several Controllers, place it in the "Shared" folder.

A View is just a class called ViewPage: it inherits from the Page class and also implements the IViewDataContainer, in order to hold all the data sent by the Controllers inside its ViewDataDictionary.
We can also send data to the View using the ViewBag dynamic dictionary, which internally uses the ViewData dictionary to store the key/value pairs, and it is an advantage because in the ViewBag case we don't need to cast the values. There is of course the disadvantage of ViewBag being late binded and therefore we don't have compile time checking but runtime errors instead. There is another useful collection named TempDataDictionary, similar to the former, with the difference that it persists ONLY between the current request and the next request (unless you mark the key to be persisted more than that, using the Keep() method). This is useful while passing data between Action methods, or in case of errors.

In this tutorial we'll learn how to use the most common HTML Helper, the TextBox control, in an MVC View in ASP.NET MVC 4, getting the following UI results:

To use the HTML Helpers we must create our own View, so first let's create a new Controller called "NewViewController", and then add a View to the Index Action method. So right click over the Controllers folder, and add a new Controller:

Name it "NewViewController", and select the template "Empty MVC Controller":

Open the Controller file and find the "Index" Action method:

Right click on it and select the option "Add View":

On the dialog, let the name be "Index", select the "ASPX" View engine, and choose a master page:

The first HTML Helpers we'll learn about are the TextBox control and the Label. For the other HTML Helpers, refer to the "Categories" Menu in the top-right place in this Blog. Open the View we just created, and type the TempData["message"] in order to display a message:

Create the Form object taking care of its tags:

Also, add a button in order to submit the form:

Now, add the label which will inform the user what is the text box about. We'll send the title text from the Action method on the server side:

Next, type the following code to display a TextBox:

The first argument the TextBox Helper gets is the name of the control: this name is the one which will identify it when the request is sent to the web server. The second argument is the text that the TextBox will display before the user types something in it. Setting it as "null" forces the MVC framework to search inside the ViewDataDictionary for some key named as the control: this way we'll send the text from the Action method on the server side. The last argument is an annonimous object which contains the style of the control.

Now let's set the Action method linked to this View. Go to the "NewView" Controller and search for the Index Action method, adding to the ViewDataDictionary the values to populate the title and the textbox control:

Now build the application and run without debugging:


As you can see, we get the title and the textbox. Open the Developer's Tools ( F12 ) and refresh the web page:

You can see in the "Network" tab, that an HTTP GET request has been sent to the web server.
Enter your name, and press the submit button:

This time, an HTTP POST request has been sent by the Form. Therefore we'll handle the request by creating an Action method which processes it and uses the same View. To handle the request, add the GetVerb and the ActionName Attributes with the following arguments:

We're just instructing the MVC framework that this is the Action method that handles POST requests, and gets the input data in the "txtUserName" textbox. Notice that the name of the parameter MUST BE EXACTLY the same of the TextBox control in order to get the data. Now we'll render a message to the client side using the input data received from the browser:

Rebuild the application, go to the browser , and type your name:


We get the message telling the user that everything went OK:

In this tutorial we've learned how to use the most common HTML Helper, the TextBox control, in an MVC View in ASP.NET MVC 4, sending to it data via the ViewDataDictionary, and the TempDataDictionary. 
That's all!! 
Happy programming.....

כתב: כרמל שוורצמן

Step By Step How to retrieve data from the request using Model Binders

         By Carmel Schvartzman

In this tutorial we'll learn how to retrieve data from the request using Model Binders in an Action method  in ASP.NET MVC 4. An Action method receives values from the HTTP request data collection, which includes data from the query string, form data, and cookies.

Each Controller has a Request and a Response properties, and from them is possible to obtain the values from the request:

Also, the MVC framework can automatically map the argument values to the Action method's parameters: the Controller looks over the sent request's parameters keys, and compares them to the names of the Action method parameters. If there is a mach, the value is assigned. If the parsing of the value fails, an exception is thrown:

The MVC framework is smart enough to deserialize an entire Entity, as follows:

That is because it uses a Model Binder, which deserializes the data request into an object, mapping every entity's public property to an request parameter, based on its key name. Also, the DefaultModelBinder keeps track of the state of the model binding, specifically of its errors. The ModelState class has a property called IsValid, which is very useful while determining the legal user input, according to data annotations of the entity.  

Finally, we can use another parameter type called FormCollection, wich contains all request data. Then is possible to call the UpdateModel method of the Controller to automatically populate the properties of an Entity with the values in the FormCollection. In order to do that, go to some Action method which handles HTTP POST requests, and take a look at the parameters: we'll use the FormCollection to initialize an Entity:

Create an instance of the same Entity sent into the request:

Now call the UpdateModel method of the Controller, to populate the object's public properties:

Next, we can for the learning sake fetch the data set by the UpdateModel method:

In an actual MVC application, we use the Repository we created in a previous tutorial , to update the post:

Let's take a look at the functionality. Build the application and browse to the Blog web page:

Press the "Edit" link to open the Edit dialog. You'll be redirected to the URL   /Blog/Edit/X  (where X is the id of the selected post):

Change some data, the Title , for example, and press "Save":


The selected post entry has been updated, using the default Model Binder:

In this tutorial we've learned how to retrieve data from the request using Model Binders in an Action method  in ASP.NET MVC. 

That's all!! 
Happy programming.....

כתב: כרמל שוורצמן