ASP.NET MVC - How to call void controller method without leaving the view?

Question

Question background:

I am implementing some basic 'shopping cart' logic to an MVC app. Currently when I click a link - denoted as 'Add To Cart' on the screen shot below this calls to an 'AddToCart' method in the 'ProductController' as shown:

Product.cshtml code:

@Html.ActionLink("Add To Cart", "AddToCart")

'AddToCart' method in the ProductController:

public void AddToCart()
{
   //Logic to add item to the cart.
}

The issue:

Not an issue as such but currently when I click the 'Add To Cart' button on the ActionLink on the ProductDetail.cshtml view the page calls the 'AddToCart' method on the ProductController and gives a blank view on the page - as shown below. I want the view to stay on 'ProductDetail.cshtml' and just call the 'AddToCart' method, how do I do this?

Answer 1

Basically @Html.ActionLink() or <a></a> tag uses get request to locate the page. Hence whenever you clicked it, you request to your AddToCart action method in ProductController and if that action method returns null or void so a blank or empty page is shown as you experienced (because or @Html.ActionLink() get request by Default).

So if you want to add your value to cart then call AddToCart method using ajax i.e:

HTML:

@Html.ActionLink("Add To Cart", "AddToCart", null, new { id="myLink"})

Jquery or Javascript:

$("#myLink").click(function(e){

    e.preventDefault();
    $.ajax({

        url:$(this).attr("href"), // comma here instead of semicolon   
        success: function(){
        alert("Value Added");  // or any other indication if you want to show
        }

    });

});

'AddToCart' method in the ProductController:

public void AddToCart()
{
   //Logic to add item to the cart.
}

Now this time when the call goes to AddToCart method it goes by using ajax hence the whole page will not redirect or change, but its an asynchronous call which execute the AddToCart action method in your ProductController and the current page will remains same. Hence the product will also added to cart and page will not change to blank.

Hope this helps.

Answer 2

The answer of Syed Muhammad Zeeshan is what you are looking for, however you may return an EmptyResult.

public ActionResult AddToCart()
{
    //Logic to add item to the cart.
    return new EmptyResult();
}

According to this it has no impact on your code ASP.Net MVC Controller Actions that return void But maybe sometime you want to return data and then you could do something like this:

if (a) 
{
    return JSon(data);
}
else
{ 
     return new EmptyResult();
}

Answer 3

As many people mentioned here you will need to use AJAX if your using asp.net MVC to hit a controller POST function without having to leave your view.

A good use case for this is if you want to upload a file without refreshing the page and save that on the server.

All of the

return new EmptyResult();

Wont work, they will still redirect you.

Here is how you do it, in your view have the follow form as an example:

            <form enctype="multipart/form-data" id="my-form">
                    <p>
                        The CSV you want to upload:
                    </p>
                    <input type="file" class="file-upload" name="FileUpload" />
                </div>
                <div>
                    <button type="submit" class="btn btn-default" name="Submit"  value="Upload">Upload</button>
                </div>
            </form>

Then in the JavaScript side you need to add this to your view with within Script tags.

  $("#my-form").on('submit', function (event) {
        event.preventDefault();
        // create form data
        var formData = new FormData();
        //grab the file that was provided by the user
        var file = $('.file-upload')[0].files[0];
        // Loop through each of the selected files.
        formData.append('file', file);
        if (file) {
            // Perform the ajax post
            $.ajax({
                url: '/YourController/UploadCsv',
                data: formData,
                processData: false,
                contentType: false,
                type: 'POST',
                success: function (data) {
                    alert(data);
                }
            });
        }
    });

Your controller might look something like this to process this type of file:

    [HttpPost]
    public void UploadCsv()
    {
        var listOfObjects = new List<ObjectModel>();
        var FileUpload = Request.Files[0]; //Uploaded file
        //check we have a file
        if (FileUpload.ContentLength > 0)
        {
            //Workout our file path
            string fileName = Path.GetFileName(FileUpload.FileName);
            string path = Path.Combine(Server.MapPath("~/App_Data/"), fileName);

            //Try and upload
            try
            {
                //save the file
                FileUpload.SaveAs(path);

                var sr = new StreamReader(FileUpload.InputStream);
                string csvData = sr.ReadToEnd();

                foreach (string r in csvData.Split('\n').Skip(1))
                {
                    var row = r;
                    if (!string.IsNullOrEmpty(row))
                    {
                        //do something with your data
                        var dataArray = row.Split(',');
                    }
                }


            }
            catch (Exception ex)
            {
                //Catch errors
                //log an error
            }
        }
        else
        {
            //log an error
        }
    }

Answer 4

There are many ways to accomplish what you want, but some of them require a lot more advanced knowledge of things like JavaScript than you seem aware of.

When you write ASP.NET MVC applications, you are required to have more intimate knowledge of how browsers interact with the web server. This happens over a protocol called HTTP. It's a simple protocol on the surface, but it has many subtle details that you need to understand to successfully write ASP.NET MVC apps. You also need to know more about Html, CSS, and JavaScript.

In your case, you are creating an anchor tag (<a href="..."/>), which when click upon, instructs the browser to navigate to the url in the href. That is why you get a different page.

If you don't want that, there are a number of ways change your application. The first would be, instead of using an ActionLink, you instead simply have a form and post values back to your current controller. And call your "add to cart" code from your post action method.

Another way would be have your AddToCart method look at the referrer header (again, part of that more subtle knowledge of http) and redirect back to that page after it has processed its work.

Yet another way would be to use Ajax, as suggested by Syed, in which data is sent to your controller asynchronously by the browser. This requires that you learn more about JavaScript.

Another option is to use an embedded iframe and have your "add to cart" be it's own page within that iframe. I wouldn't necessarily suggest that approach, but it's a possibility.

Answer 5

Controller should return ActionResult. In this case a redirect to the caller page.

Answer 6

• using System.Web.Mvc;

• using System.Web.Mvc.Html;

  public ActionResult Index()
  {
      HtmlHelper helper = new HtmlHelper(new ViewContext(ControllerContext, new WebFormView(ControllerContext, "Index"), new ViewDataDictionary(), new TempDataDictionary(), new System.IO.StringWriter()), new ViewPage());
      helper.RenderAction("Index2");
  
      return View();
  }
  
  public void Index2(/*your arg*/)
  {
      //your code
  
  }
  

Answer 7

I was struggling with this and couldn't get it working with ajax.

Eventually got a working solution by making my controller method return type ActionResult rather than void and returning a RedirectToAction() and inputting the action relating to the view I wanted to remain on when calling the controller method.

public ActionResult Method()
        {
            // logic

            return RedirectToAction("ActionName");
        }