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ASP.Net MVC Tip: URL Anchor Tags

Tuesday, 6 December 2011 7:11 pm Comments off

This is one of those features which should be baked into MVC by default, but isn’t.

Actually, it is partially supported by MVC. This Codeplex answer details it:

 

@Html.ActionLink(
    "Link Text",           // linkText
    "Action",              // actionName
    "Controller",          // controllerName
    null,                  // protocol
    null,                  // hostName
    "fragment",            // fragment
    new { id = "123" },    // routeValues
    null                   // htmlAttributes
)

will produce (assuming default routes):

<a href="/Controller/Action/123#fragment">Link Text</a>

But what if you want the returned redirect of an ActionResult method to include the anchor tag. There is no RedirectAnchorTagResult to return.

 

That same answer does some voodoo to pull it off:

public ActionResult Index()
{
    var url = UrlHelper.GenerateUrl(
        null,
        "Action",
        "Controller",
        null,
        null,
        "fragment",
        new RouteValueDictionary(new { id = "123" }),
        Url.RouteCollection,
        Url.RequestContext,
        false
    );
    return Redirect(url);
}

 

It is this that should be baked into MVC by default. Thats an awful lot of complexity to expose just for the sake of a simple anchor tag. So, yes, a RedirectAnchorTagResult would be a nice addition.

 

Thanks to Darin Dimitrov for providing the answer. Go ahead and upvote his answer.

Categories: Codeplex, MVC, Programming, Tech

Codeplex Projects of the Week.

Wednesday, 30 November 2011 11:00 pm Comments off

Two Codeplex projects have come in quite handy for  me this week and I thought I’d pass them on.

 

WSUS 3.0 – WSUS Smart Approve

I installed Windows Server Update Services on my Windows Home Server 2011 this week.

As usual, I was in a bit over my head. I hit the Approve All Updates nuclear option. Knowledgeable sysadmins are possibly cringing or screaming at me (or both). By the time i figured out that approving updates puts them in the download queue, 4 and a half gigabytes were in the queue. Ordinarily this wouldn’t be a problem. But my broadband has had issues and it’s ridiculously slow (0.85 MBPS) and WSUS was eating up all the bandwidth.

So this was a problem. The solution was, of course to approve and download only needed updates. Amazingly, WSUS has no way of automatically approving needed updates (even as a checkbox buried five or six option screens down and off by default).

So, Codeplex to the rescue!

WSUS Smart Approve does exactly what it says on the tin – automatically approving updates according to certain rules. One of those is, of course, to approve needed updates automatically.

 

MetaWeblogAPI – ooMetaWeblog

One of the nice things about the MetaWeblogAPI is that almost everyone supports it. One of those is, of course, Windows Live Writer 2011.

Using Windows Live Writer as a WYSIWYG editor would be convenient.

There are a number of options to implement a server-side MetaWeblogAPI endpoint. Scott Hanselman has one approach.

I used another approach  – the Matlus.MetaWeblogAPI.

The corresponding Codeplex project is ooMetaWeblog.

 

Hope they come in helpful for somebody.

Why Silverlight Should Stay

Tuesday, 8 November 2011 9:04 pm Comments off

Mary Jo Foley just published a post discussing the future of Silverlight.

I’m not a Silverlight Developer by any stretch of the imagination. I never played with it. Never touched it at all.

Then, for the Flying Shakes website,  I had to have the control below in a web form. Naturally I turned to Silverlight.

image

 

With no knowledge or experience of Silverlight it took me 90 minutes from idea to working control.

And yes, I realise that I could write a HTML5 version of that now. But it would probably take much, much longer (don’t nobody suggest Flash).

Silverlight is good, not just for rich client experiences it allows us to build, but also because its part and parcel of the tools we Visual Studio devs work with every day.

The flip side to this, of course is the user perspective.

Here in the UK we have Sky satellite television. The reason why I like them so much is that they are fairly technology friendly. Besides streaming on the go (iPad, iPhone, etc), you can log on to their Sky Go website to stream on-demand or download and watch on your desktop offline.

This experience is delivered by, wait for it, Silverlight. The impressive part of this whole thing was the Sky Go Desktop Client. Its an offline Silverlight application, popping straight out of the browser and installed silently.  Was downloading from my queue 10 seconds after hitting the download button.

Satisfied does not even begin to describe it.

I HTML 5 may be the bees knees, but there is still a business case for keeping Silverlight around.

I’ll consider HTML 5 a contender when we have the same level of support and tooling for it as we have now for Silverlight.

LINQ + Google Charts + MVC : Pie Chart

Tuesday, 1 November 2011 3:52 pm 1 comment

A couple of weeks ago, I pointed out a LINQ snippet that was running against the Google Charts API.

This week, I’m back with my implementation of  the Pie Chart.

I’ve started with the Pie chart because its relatively simple and will lay the foundation for dealing with the complexities of the other charts.

Building Blocks

Since this is MVC, I created a new ChartsService class in the Services namespace of the project.

If you look at the snippets in the original ACM article, you’ll notice an extension method called “SeparatedBy”. So our first task is to create this extension method.

There are, of course, a number of ways to concatenate a list of string with a separator. This being an exercise in LINQ, we are going to use the LINQ Aggregate method.

   
public static string SeparatedBy(this List<String> list, string seperator)
{ 
return list.Aggregate((current, next) => current + seperator + next); 
}

 

I’m sure that you’ll agree with me when i say that it’s a nice and clean approach to what could be a messy block of code.

However, that extension method will only concatenate the list of strings passed to it. Why is this a problem? Because we are going to want to concatenate lists of int objects as well. So that extension method will just not do. We  could do some fancy work with generics, but the simplest thing to do is to supply to an overloaded method that accepts lists of type int.

public static string SeparatedBy(this List<int> list, string seperator)

List<string> thelist = list.ConvertAll<string>(x => x.ToString());

 return thelist.Aggregate((current, next) => current + seperator + next); 
}

There is one additional difference between these and our original method – the call to ConvertAll. Rather than have a foreach loop that does the conversation, we simply supply an inline lambda function that gets executed against each item  in the list and returns a list of the desired type. Again, very clean.

 

So, armed with these extension methods, we can now declare our classes.

Data

Google charts offers a wide range of functionality and many different kinds of charts. Each chart has a host of differing options and settings available to it. So when creating classes to represting thse charts kinds we have to bear in mind that there will be unique functionality not common to other charts that will come up.

Charts logically are made up of a number of  smaller complements:  bar charts have columns, pie charts have slices and so on and so forth. So we’ll represent these first.


public class Slice
{
public int Value { get; private set; }
public string Legend { get; private set; }

public Slice(int value, string legend)
 this.Value = value;
this.Legend = legend;
}

} 

Lets first look at the Pie class itself now.

Pie Class


public List<Slice> Slices { get; set; }
public string Title { get; private set; 
public Double Height { get; private set; }
public Double Width { get; private set; }

public Pie(string title, double height, double width)
{
this.Slices = new List<Slice>();
this.Title = title;
this.Height = height;
this.Width= width;
}

We start by declaring a number of properties and a constructor. In the constructor we initialize our list of Slices. This is where we see a departure from the snippets of he ACM article.  We do not pass the slices into the constructor. Of course, this is an issue of style over substance. There is no reason why we could not have generated the slices before the creating the chart and then passed the slices.


public string Compile()
{
var tt = Title.Split(' ').ToList().SeparatedBy(' ');
var p = new List<string>(){
this.Slices.Select(slice =>slice.Legend).ToList().SeparatedBy("|"),
this.Slices.Select(slice =>slice.Value).ToList().SeparatedBy(",")};

return string.Format(@"http://chart.googleapis.com/chart?cht=p&chtt={0}&chs={3}x{4}&chl={1}&chd=t:{2}", tt, p.ElementAt(0), p.ElementAt(1), this.Width, this.Height)
}

This is where all the important stuff happens.

Line 3 properly formats the title by putting a + sign to signify spaces between words. Note that we are using the extension method we wrote earlier.

Line 4 creates a new list of strings, each string being the comma or | delimited list of values and legends. Using a List gives us greater flexibility later on when our implementation will handle multiple data series and legends

Line 8 uses String.Format to merge all this data into a url that we can use to call the Google Charts API with. For an explanation of what each of these parameters mean, see the Google Charts API Parameter List

 

ViewModel

Now, this being MVC, the way to display stuff is by using a ViewModel. So lets create one:


public class MonthlyReportsViewModel
{
public MonthlyReports Details { get; set; }
public Pie Chart { get; set; }
 }

The one property we are interested in here is the Chart Property.

Now that we have our ViewModel, we have to populate it. So, in our ActionResult method:


<pre>Pie chart = new Pie("This is my chart",200);
chart.Slices.Add(new Slice(25, “Slice 1”));
chart.Slices.Add(new Slice(25, “Slice 2”));
chart.Slices.Add(new Slice(25, “Slice 3”));
chart.Slices.Add(new Slice(25, “Slice 4”));
model.Chart = chart;
return View(model);

 

View

In our View itself, we’re going to have to render out the chart. Since the call to Google Charts API will return an image, we can simply do the following:


<img src = "@Model.Chart.Compile()" alt ="">

 

What one could do is to put the actual rendering code in a Helper Method and call the Helper Method from your view, like so:


@GoogleCharts.PieChart(@Model.Chart)

That, of course, further abstracts the code. It does have the advantage of being much cleaner and easier to do.

 

Conclusion

As you can see, using LINQ to abstract away the complexity of what your code is actually doing is not just the province of database code. One thing what I’ve enjoyed about working with LINQ is how code always comes out looking fresh, clean and crisp. Having worked extensively with LINQ and Lambda expressions, using foreach loops  to process Lists looks so much messier.

Next time, we’ll take a look at the somewhat more complicated Bar Chart. I’ll not cover every single possible piece of functionality, but I’ll cover the basics. All I want to show is how the foundation laid down today can easily translate over. My current implementation of bar charts is sufficient only for the limited functionality the app needs and nothing more. 

At some point in the future, I’d also like to implement Line charts.

 

Postscript

I must say that apart from working with LINQ, its been a very satisfying experience for me to implement a C# version of a web API.

There is GoogleChartsSharp on Codeplex that Implements a whole lot more of the functionality of Google Charts. I did indeed use it for a while before implementing it on my own.

So its been a satisfying experience for me to implement an API that allows me to work the way I want to work. Not only did I write something simpler and easier to work with, but I dropped a dependency in the process and that made me happier than I think its safe to admit. 

Writing against something requires you, the writer, to pay extra attention to the small details. It requires you to think of the relationship between your code,the web API  calls and the documentation that supports it. When one uses an already baked implementation such as GoogleChartSharp, its like working with a giant black box  you have no idea what goes on inside. And you really don’t want to know the finer details. But writing the API, you create a white box. And you HAVE to understand those finer details.

So while the LINQ is nothing special in and of itself,nothing earth shattering or ground-breaking, it is the experience and the satisfaction gained from it that makes this a worthwhile post to write.

Categories: Google, LINQ, MVC, Programming, Projects, Tech, Web

LINQ Goodness: Google Charts Edition

Monday, 3 October 2011 7:35 pm Comments off

My day job (one of them, anyway) is to design*, run and maintain Flying Shakes

If someone had told me when I started  that 90% of the code (and 87.653% of all stats are made up, but you get my drift) I’d write would be for the administration side of things, I’d never have believed it.

 

Anyway, to cut a long story short, it was in this context that I came across a fascinating article from the Association for Computing Machinery (and no, I have not heard of them before either). I came across this a month or so ago, but lost the link.

 

With a little bit of Google-fu, I’ve found it once again: The World According to LINQ.

While its a fascinating article that appeals to the Computer Scientist in me (supposedly useless classes on in-depth database theory tend to do that), what caught my eye was the code sample right at the bottom for generating Google Chart Url’s.

That sample is going to come in very handy for me and I thought I’s share it with you.

Go ahead and read the article.

 

*If you see me ranting on Twitter or Google+ about CSS, this is probably why.

Categories: LINQ, Programming, Software, Tech

WCF Chat Update: Long Polling

Tuesday, 30 August 2011 7:28 pm Comments off

Updating WCF chat continues slowly but surely. I have not made any commits yet, so you’ll have to wait to see the changes.

In addition to the changes to Authentication, there are changes to the callback mechanism that I originally wrote.

 

When i originally wrote the chat application, the callback was one of the first pieces of code that i wrote. The fact of the matter is, the the only requirement for it was to work across the local network (or even simply between instances on the local machine). So when I wrote the Cloud version, suddenly callbacks had to work across NAT to let the application function across the internet.

 

Now, there are a number of possible design patterns that would allow the server to execute a callback on a remote client. 

 

The first is ,indeed, the design pattern we use at the moment. Where we actually have a callback. the enabler for this is actually found in WCF. The wsHTTPDuplexBinding allows for dual HTTP connections – one in each direction. This allows you to invoke an operation on the client. However, in order for this to work, you need to have an instance of WCF server on a per-instance basis. So. Every new client session will spawn a new instance of the server. This means that you are going to end up with dozens ( or hundreds etc) of long-lived instances. The question here is scalability. Is this scalable?

It might seem somewhat arrogant to talk about scalability, but if you design with scalability in mind, you’re not going to end up dealing with it later.

 

The other is something that, while not new, really hit the big-time after Friendfeed released its Tornado server. Tornado supports long polling http connections. Long polling is not in and of itself new. The basic design pattern involves a client making a call ( http or otherwise) to a server. The server receives the connection and keeps it open until it has something to return. Some long polled connections eventually time out and this is the implicit signal for the client to immediately open another connection. Others, such as the Friendfeed implementation, keep them open indefinitely.

 

There are probably more that you can think of, but these are the two that I considered for the Chat Application. As with most things, the choice is between a Push model (where notifications are pushed to the client) and the Pull model (where information, Notifications or otherwise, is pulled from the server by the client).

 

The fact of the matter is that I like both. Both are Cool. And both are supported intrinsically by WCF – no coding voodoo to make thins work.

Of the two, I’ve begun implementing the long polling method. Although it s radical departure, it will allow the overall design of to server-side to remain the same. The WCF server remains as a Single Instance service, and so the implementation remains the same.

The WCF stack is written in such a way that when you mark a OperationContract as needing the Async Pattern, WCF with start the Asyc operation and then go off and handle another request until that method returns. The End method that receives the results then returns the data to the client. In other words, its non-blocking.

I’ve not sorted out the exact specifics of implementation, but there will be changes to both the server and the client to accommodate  this. In saying that, I’m doing  a lot of simplification to the class structure. So hopefully what emerges from all these changes will be better than the current setup. Even I had to go back and follow the inheritance tree to figure things out.

These changes are happening in parallel with the changes to the authentication scheme.

 

So, while I’ve got no code, I leave you with this MSDN blog post on Async programming with WCF and this post that adapts it to long-polling specifically.

Some Interesting Code – your thoughts required

Thursday, 18 August 2011 11:22 am Comments off

Without going to into a long story, I found some interesting code here to convert anonymous types to any strongly typed, well, type.

 

public static object ToType<T>(this object obj, T type)
{

    //create instance of T type object:
    var tmp = Activator.CreateInstance(Type.GetType(type.ToString())); 

    //loop through the properties of the object you want to covert:          
    foreach (PropertyInfo pi in obj.GetType().GetProperties()
    {
      try 
      {   

        //get the value of property and try 
        //to assign it to the property of T type object:
        tmp.GetType().GetProperty(pi.Name).SetValue(tmp, 
                                  pi.GetValue(obj, null), null)
      }
      catch { }
     }  

   //return the T type object:         
   return tmp; 
}

From this codeproject article.

Anyone have any thoughts on this?  Is it good? Bad? Inefficient? Crap??

Categories: Programming, Software, Tech
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