How to keep the same data when return to the view? - asp.net-mvc-3

Question

How to keep the same data when return to the view?
I tried to put return the form to the view, but it did not work.
Is there any good and simple way to do this?
[HttpPost]
public ActionResult Register(FormCollection form)
{
string name = form["Name"].Trim();
if (string.IsNullOrEmpty(name))
{
TempData["TempData"] = "Please provide your name ";
return View(form);
}
string email = form["Email"].Trim();
var isEmail = Regex.IsMatch(email, #"(\w+)#(\w+)\.(\w+)");
if (!isEmail)
{
TempData["TempData"] = "Sorry, your email is not correct.";
return View(form);
}
//do some things
}

Answer 1

Not sure why you would be using FormCollection in the post but maybe you come from a WebForms background. In MVC you should use ViewModels for the transport of your data to and from the Views.
By default the Register method in an MVC 3 app uses a ViewModel in the Register View. You should simply post it back. In fact, the default app has that already created for you if you didn't know as part of the Internet template.
The standard pattern is to have a ViewModel that represents your data that you will use in your View. For example, in your case:
public class RegisterViewModel {
[Required]
public string Name { get; set; }
[Required]
[DataType(DataType.EmailAddress)]
[Display(Name = "Email address")]
public string Email { get; set; }
}
Your controller the should contain 2 actions, a Get and a Post. The Get renders the View and is ready for the user to enter data. upon submitting the View the Post action is then called. The View sends the ViewModel to the action and the method then takes action to validate and save the data.
If there is a validation error with the data, it's very simple to return the ViewModel back to the View and display the error messages.
Here is the Get action:
public ActionResult Register() {
var model = new RegisterViewModel();
return View(model);
}
And here is the Post action:
[HttpPost]
public ActionResult Register(RegisterViewModel model) {
if(ModelState.IsValid) { // this validates the data, if something was required, etc...
// save the data here
}
return View(model); // else, if the model had validation errors, this will re-render the same view with the original data
}
Your view would look something like this
#model RegisterViewModel
#using (Html.BeginForm()) {
#Html.ValidationSummary(true)
<div class="editor-label">
#Html.LabelFor(model => model.Name)
</div>
<div class="editor-field">
#Html.TextBoxFor(model => model.Name) <br />
#Html.ValidationMessageFor(model => model.Name)
</div>
<div class="editor-label">
#Html.LabelFor(model => model.Email)
</div>
<div class="editor-field">
#Html.TextBoxFor(model => model.Email) <br />
#Html.ValidationMessageFor(model => model.Email)
</div>
}
Using other strategies to capture and save data in an MVC app is absolutely possible, it's a very extensible framework. But there is a specific pattern that makes MVC what it is and working against that pattern can sometimes prove difficult. For a beginner it is best to understand the preferred patterns and strategies first and then once understood very well, you can then adopt some of your own custom strategies to meet your needs. By then you should understand the system well enough to know what you need to change and where.
Happy coding!!