Export .sdif file to the client’s desktop

One of the user requirements of the swim team website is to send the .sdif file that I blogged about here from the webpage to the user’s browser – or download it to the users file system. Since the file is dynamic and I can’t write to the file system of the web server, I need a way to generate the file and then have a dialog box “Save To” open.

The first step was to add a UI project to the solution that matches the MVC project that the swim team currently users. I love the organization of the initial project – it was very easy and logical to drop in a new Web project:

I then opened up the home controller and added a base method and ported the code from the Console UI:

        [HttpPost]
        public ActionResult GetSdifFile()
        {
            string fileName = @"C:\Users\Public\PracticeMeetSetup.SD3";
            MeetSetupFactory factory = new MeetSetupFactory();
            Collection<string> collection = factory.CreateMeetSetUp(72);
            File.WriteAllLines(fileName, collection);
            return View();
        }

Basically, I need to rip out the disk write code and replace it with something that can go to the browser. Being a traditional ASP.Net guy, I immediately thought of something like this:

        public void Guess(string filePath)
        {
            try
            {
                using (StreamReader sr = new StreamReader(filePath))
                {
                    String line;
                    while ((line = sr.ReadLine()) != null)
                    {
                        Response.Write(line + "<br />");
                    }
                }
            }
            catch (Exception ex)
            {
                Response.Write("<p>The file could not be read:");
                Response.Write(ex.Message + "</p>");
            }
        }

I then thought “Wait, this is MVC…” so I thought of something like this:

        [HttpPost]
        public ActionResult GetSdifFile()
        {
            MeetSetupFactory factory = new MeetSetupFactory();
            Collection<string> collection = factory.CreateMeetSetUp(72);
            return View(collection);
        }

And the view displaying the contents of the collection:

    <h2>GetSdifFile</h2>
        <% foreach (string _currentString in Model){ %>
            <%= Html.Encode(_currentString) %>
            <br />
        <% } %>

And here are the results:

So it is a start – I guess they could copy/paste the contents of the page. However, the User Case is for them to click a button and get a .sdif file that saves to their file system (via, I assume, a Save Dialog box).

I wrote a new function that returns JSON:

        public JsonResult CurrentMeetSdifFile()
        {
            MeetSetupFactory factory = new MeetSetupFactory();
            Collection<string> collection = factory.CreateMeetSetUp(72);
            JsonResult result = new JsonResult();
            result.Data = collection;
            result.JsonRequestBehavior = JsonRequestBehavior.AllowGet;
            return result;
        }

Since the browser doesn’t know what to do with JSON (I only tested in IE), then you get a save dialog box:

Saving that to the desktop, I open in note pad and get the following results:

The results are losing their line formatting.

This is the right track – but I have bit more work to do.

My 1^st step was to add a parameter of the actual meet that the user wants:

        public JsonResult CurrentMeetSdifFile(int meetId)
        {
            MeetSetupFactory factory = new MeetSetupFactory();
            Collection<string> collection = factory.CreateMeetSetUp(meetId);
            Etc…
        }

I then tried it from the browser:

Ugh, it looks like with the default routing engine, I need to make the parameter have the name id. I have a choice. I can either add a new route with an explicit meetId or I can use the id variable name. I chose option B as a path of least resistance:

        public JsonResult CurrentMeetSdifFile(int id)
        {
            MeetSetupFactory factory = new MeetSetupFactory();
            Collection<string> collection = factory.CreateMeetSetUp(id);
            JsonResult result = new JsonResult();
            result.Data = collection;
            result.JsonRequestBehavior = JsonRequestBehavior.AllowGet;
            return result;
        }

With the routing set up, I now need to fix the JSON output to stick a new line after each string in the collection.

My 1^st attempt was just to throw an Environment.NewLine into the Json result:

Yikes! It looks like I am mixing formatting. “\r\n” is coming down as a literal value. I need a way to tell notepad that they are line breaks.

I binged around a bit and looked at attack overflow. This post seems to have the answer. I tried to add

result.ContentType = "text/html";

But then the browser displayed the data:

Note the “\r\n” is still there.

I then tried some other ways of breaking (using the \\n for example), nothing.

I then stepped back and thought that I was approaching the problem incorrectly. Instead of sending back JSON from the function, what if I sent something else? A quick tour through MSDN showed me a file result class. That is what I need and here is an example of my question.

A quick run through the overloads of the method, I realized that all I have to do is to convert the string collection into a FileStream and then send it out via the File class. I used the FileStreamResult class and the rest was pretty easy to wire up:

        public FileStreamResult CurrentMeetSdifFile(int id)
        {
            MeetSetupFactory factory = new MeetSetupFactory();
            Collection<string> collection = factory.CreateMeetSetUp(id);
            StringBuilder stringBuilder = new StringBuilder();
            foreach(string _currentString in collection)
            {
                stringBuilder.Append(_currentString);
                stringBuilder.Append(Environment.NewLine);
            }
 
            byte[] byteArray = Encoding.ASCII.GetBytes(stringBuilder.ToString());
            MemoryStream stream = new MemoryStream( byteArray ); 
            FileStreamResult fileStreamResult = new FileStreamResult(stream,"text/plain");
            return fileStreamResult;
 
        }

And if I want to get the popup, I change the output format to “.sdif” and I get the dialog box with the data formatted correctly.

And boom goes the dynamite…

MVC Route Constraints

I started to dig into MVC3 routing a bit more over the weekend.  I came across some routing constraints and realized that there is a clear progression.  I created an out of the box MVC3 web application (I am using Razor) and then added a Product Controller with the default methods and 1 View for the Details method.  I made 1 change to the out of the box convention – I changed the name of the int parameter to the Details method to productId.

The Details controller method pushes the parameter back out to the View:

        public ActionResult Details(int productId)
        {
            return View(productId);
        }

and the view parrots the productId back to the user:

@{
    ViewBag.Title = "Details";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Details</h2>
<br />
You Entered =  @Model

I then dropped into Global.asax to work with the constraints.  The first thing I did was to add a route to the routing table to account for the productid parameter:

            routes.MapRoute(
                "Product",
                "Product/{productId}",
                new { controller = "Product", action = "Details" }
            );

This worked fine to a point.  Product/1 resolved:

but Product/foo was allowed by the routing engine and the method threw an error:

To handle this malformed parameter, I added a regular expression to the constraint definition (using Stephen Walter’s blog post as an example:

            routes.MapRoute(
                "ProductWithConstraint",
                "Product/{productId}",
                new { controller = "Product", action = "Details" },
                new { productId = @"\d+" }
            );

Now, when Product/foo comes in, I got a 404.

The next scenario I wanted to handle was that only some integers are allowed as a parameter.  For example, perhaps only products that are in stock are allowed – which means that you need to do a database call before defining the route constraint definition.  To that end, I created a new class that inherited from IRouteConstraint (based on Yuri Nayyeri blog post):

    public class ProductRouteConstraint: IRouteConstraint 
    {
        public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values, RouteDirection routeDirection)
        {
            if ((routeDirection == RouteDirection.IncomingRequest)
                && (parameterName.ToLower(CultureInfo.InvariantCulture) == "productid"))
            {
                int productId = 0;
                try
                {
                    productId = Convert.ToInt32(values["productId"]);
                    if (productId > 0 && productId < 10)
                    {
                        return true;
                    }
                }
                catch (FormatException formatException)
                {
                    return false;
                }
            }
            return false;
        }
    }

I then added this constraint to the routing table:

            routes.MapRoute(
                "ProductWithConstraintClass",
                "Product/{productId}",
                new { controller = "Product", action = "Details" },
                new { productId = new ProductRouteConstraint() }
            );

And I got the desired result – products less than 0 or greater than 10 returned a 404.

So the progression in my mind is:

1. No constraints
2. Reg Ex constraints in the Global.asax
3. Create a class that implements IRouteConstraint

I my mind, I would rather skip #2 and go to #3 altogether.  Having all of the logic encapsulated in 1 class seems cleaner and not having the Global.asax mucked up with custom defs makes for a more maintainable solution.

MVC, LINQ, and WinHost

I love MVC. I recently had to make some changes to the swim team website to get ready for the 2011 season. Because there was a nice SOC enforced by MVC, I simply had to add a couple of new controllers with some basic CRUD:

add their associated views, and then wire up to my factory using my POCOs:

        public ActionResult Index(int? page)
        {
            FamilyFactory familyFactory = new FamilyFactory();
            IQueryable<Family> families = familyFactory.GetAllFamilies()
                .OrderBy(family => family.FamilyDesc)
                .AsQueryable <Family>();

            const int pageSize = 10;
            var paginatedFamilies = new PaginatedList<Family>(families, page ?? 0, pageSize);

            return View(paginatedFamilies);
        }

(note that I used the paginated list from Nerd Dinner)

Boom goes the dynamite.

Upon reflection, you can really see how useful using POCOs are when you have to extend your application. That upfront cost 2 years ago is paying huge dividends now.

I did run into 1 small hiccup when I deployed to WinHost. I received the following error:

After some digging (this error does not Google well), I added this:

<trust level="Full" />

To System.Web and things corrected.