CTE , ROW_NUMBER() PARTITION BY , useful tools when face with duplicate data

I recently came across an issue where I was retrieving data for a UI and dealing with potential dupes. for my purposes I used CTEs and row_number function to solve my particular issue.

 A CTE is essentially a kind of temporary table or a named result set off of a physical table (sort of like an in-line view).

With this function, you can number rows in your result set.  Even better, you can PARTITION BY to split your result set up into groups.  I might not want to see 1-10 as my row numbers, I might want to see 1-5 and 1-5 based on some column that I decide to partition the data by.  Note, this is a horizontal partition of rows.




 

 

A closer look -Enumerable.Range (System.Linq)

Enumerable.Range is a small static method in the  Enumerable class from System.Linq. 

The Enumerable.Range() method performs a very simple function, but it’s results can be used to drive much more complex LINQ expressions.  In it's simplest form it can be used to generate a sequence of consecutive integers. 

It accepts two int parameters, start and count, and constructs a sequence of count consecutive integers, starting at start:

• Range(int start, int count)

• Returns a sequence of int from start to (start + count – 1).

So, for example, the code snippet below will create an List<int> of the numbers from 1 to 10:

   1: var numbers = Enumerable.Range(1, 10).ToList();

   2: string nums= string.Join(",", numbers); 

   3: // result will be : "1,2,3,4,5,6,7,8,9,10"

Not just for numbers !

Or it can be used to  to generate a string containing the English alphabet

   1: IEnumerable<char> letters = Enumerable
   2:  .Range(0, 26)
   3:  .Select(x => (char)(x + 'a'));

   4: string alphabet = string.Join("", letters); 

   5: // result will be : "abcdefghijklmnopqrstuvwxyz"

Handy eh ?

Getting a bit more complicated now, if we wanted a list of the first 5 even numbers, we could start with the number of expected items and use the .Select() clause in conjunction with the mod operator to bring back only the even numbers :

   1: var evens = Enumerable.Range(0, 5).Select(n => n*2).ToList();

   2: string ans = string.Join(",", evens ); 

   3: // result will be : "0,2,4,6,8"

Alternatively , you can achieve the same result using the .Where() clause against the total results to filter it down:

   1: var another= Enumerable.Range(0, 10).Where(n => (n % 2) == 0).ToList();

   2: string ans = string.Join(",", another); 
   3: // result again will be : "0,2,4,6,8"

Or if you want to provide a min value, max value, and a number of steps, as demonstrated in this question on StackOverflow and answered by by John Skeet:

i.e. basically what was needed here was to return something like this :

0, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000

Were the min was 0 , the max 1000 , and he wanted to get there in 11 steps.

   1: int numberOfSteps = 11, max = 1000, min = 0;
   2: var example = Enumerable.Range(0, numberOfSteps)
                 .Select(i => min + (max - min) * ((double)i / (numberOfSteps - 1)));
   3: string ans = string.Join(",", example); 
   4: // result will be : "0,100,200,300,400,500,600,700,800,900,1000"








Conclusion

The Enumerable.Range() method performs a very simple function, but it’s results can be used to drive much more complex LINQ expressions.

Displaying SSRS Report in MVC using MvcReportViewer -Part II

Embedding a Local Report

In my previous post we discussed how to install the MVCReportViewer package via Nuget into your application to avail of the helpers to embed SSRS reports into your MVC views.

In this article we will discuss using the MVCReportViewer  package and helpers to embed local reports.

Most often people want to embed SSRS reports from the server into thier views, but sometimes we just want to create a simple local report in Visual Studio and display that in our view. This is the scenario we will discuss below.

Creating reports in Visual Studio 2012/2013

Visual Studio 2012/2013 comes with reporting capibilites out of the box. Simply right click in your solution explorer in Visual Studio and Add Item/ Reporting and you can see you have the option to add a Report or use the Report Wizard.

This provides you with good basic reports, it's like a pared down version of the tools and controls you get with real SSRS. If this suits your needs you need go no further. However if you need more capilibilites than whats on offer here you will need to install the SQL Server Data Tools – Business Intelligence tools  for Visual Studio 2012/2013.

SQL Server Data Tools – Business Intelligence for Visual Studio 

Currently the URL to download Microsoft Visual Studio Tools for Applications component for Visual Studio 2012 can be found here:

http://www.microsoft.com/en-ca/download/details.aspx?id=38807

Once you have install it, you will be able to create and work with SSRS reports within Visual Studio. Here are the basic steps for setting up a new SSRS report project:

Open up Visual Studio

• Select File –> New –> Project
• You will now see a new project template option called Business Intelligence
• Expand this project template and select the Reporting Services option.
• You can now either choose to use the setup wizard or just a plain project template.

Regardless of whether your requirements necessitate the use of the Business Intelligence tools or the standard out of the box reporting tools in Visual Studio, lets now disucss adding a basic report to your project so you can embed it in your MVC view.

DataSets

Before creating your report, you need to define your dataset. Lets create a Report folder in our project. It is a good idea to organise your folder structure within your application in a logical manner , so we will use this folder for all our Datasets and reports.

Using the standard out of the box reporting functionality in Visual Studio 2012/2013, right-click in your Report folder and Add New item.

Go to Data-> and select Dataset. Call it 

Displaying SSRS Report in MVC using MvcReportViewer -Part I

In this article we will discuss installing the MVCReportViewer package into your MVC application to get it ready to embed reports. 

In Part 2 , we will discusss embedding local reports into your MVC application and in Part 3 we will discuss the changes needed to embed reports from yourn SSRS server.

Embedding SSRS or indeed local RDLC reports into a  view in an ASP.NET MVC application is easy using the MVCReportViewer package , and the HTML Helpers it comes with.

The first step to get the MVCReportViewer package installed into your project , to do this you can use the Package manager console in Visual Studio , using the following command:

PM> Install-Package MvcReportViewer

This will add the relevant scripts, Web.Config app settings and report viewer appx to your MVC Application which are needed to embed your reports into your views.

After sucessfully installing the MVCReportViewer package you will notice some changes to your application. 

The following App settings for the report viewer have been added to your Web.Config:


<add key="MvcReportViewer.AspxViewer" value="/MvcReportViewer.aspx" />
<add key="MvcReportViewer.AspxViewerJavaScript" value="~/Scripts/MvcReportViewer.js" />
<add key="MvcReportViewer.ErrorPage" value="~/MvcReportViewerErrorPage.html" />
<add key="MvcReportViewer.ShowErrorPage" value="true" />

<add key="MvcReportViewer.ReportServerUrl" value="http://localhost/Reportserver_SQLEXPRESS" />
<add key="MvcReportViewer.Username" value="" />
<add key="MvcReportViewer.Password" value="" />
<add key="MvcReportViewer.EncryptParameters" value="false" />
<add key="MvcReportViewer.IsAzureSSRS" value="false" />

<add key="MvcReportViewer.LocalDataSourceProvider" value="MvcReportViewer.SessionLocalDataSourceProvider, MvcReportViewer" />


Key settings to note here , are the AspxViewer setting, which points to the aspx page which has also been installed by the NuGet package . It is this page that will be used to display our report in an iframe. 

The ReportServerUrl and LocalDataSourceProvider settings are important depending on wehther you want to embed a server report or a local one. I will use both later on when i give examples of both scenarios.

And that's it, now you are ready to embed a server or local report into your MVC views. See the following articles for examples of both.

Know It, Prove It

Anyone else doing the "Know It, Prove It" challenge on the Microsoft Virtual Academy site this February ? I'm half way through the Web Development challenge and really enjoying it.



http://www.microsoftvirtualacademy.com/LearningPaths/Dashboard.aspx

Even if you're not taking part in the challenge, all the courses on the Virtual Academy are free and i highly recommend watching Learn-html5-with-javascript-css3-jumpstart-training with Michael Palermo and Jeremy Foster if you have a hour or two to spare. Its also recommended viewing for the Microsoft Exam 70-480 Programming in HTML5 with JavaScript and CSS3 if you're taking this Certification.

Output Caching in ASP.NET MVC4

You can dramatically improve the performance of your ASP.NET MVC application very easily by taking advantage of the built-in output caching attributes. If you have an application that gets alot of traffic on a specific page , or returns a large list of records from a database you can use the output caching mechanism to cache the content returned by a controller action. And in doing so the same content does not need to be generated each and every time the same controller action is invoked causing unnecessary database hits and slowing down your page.

Most Output caching can be implemented very easily in MVC4 by using the standard OutputCacheAttribute class without having to go down the route of building a custom output cache provider. By decorating your controller actions with the outputcache attributes , you can maintain control over the duration of the cache of your actions.

First off , it's important to note that by default actions in asp.NET MVC have a cache-control of private.Which you can see by creating a simple action like the one below :

public JsonResult Details(int id)

{

////code here to get your results for your id

return Json(result, JsonRequestBehavior.AllowGet);

}


And then checking the header in the response in Fiddler or your tool of choice , and  you will see the cache-control :

Cache-Control:private

Connection:Close

Content-Length:81836

Content-Type:application/json; charset=utf-8

Date:Mon, 29 Oct 2012 08:08:44 GMT

Server:ASP.NET Development Server/11.0.0.0

X-AspNet-Version:4.0.30319

X-AspNetMvc-Version:3.0

This means that the browser might cache such ajax request made by a JavaScript client, which most of the time might not be desired. And can result in unexpected behaviour , especially in IE which is cache hungry. So often it is desirable to control what is cached and when yourself just to have some confidence in what is going on.

ASP.NET MVC Build-in caching mechanism

 You can control output caching by using the build-in output cache in asp.NET MVC. To do this you can decoration your controller actions with the outputcache attribute as follows.

[OutputCache(Duration = 6)]

public ActionResult Search(string searchText)

{

return Json(SearchWebService.MyWebServiceInstance.AutocompleteSearchClient(searchText),JsonRequestBehavior.AllowGet);

}

Now if we check our headers again , we can see our cache-control change :

Cache-Control: public, max-age=6

Expires: Mon, 29 Oct 2012 09:18:37 GMT

Last-Modified: Mon, 29 Oct 2012 09:18:34 GMT

Connection:Close

Content-Length:81836

Content-Type:application/json; charset=utf-8

Date:Mon, 29 Oct 2012 08:08:44 GMT

Server:ASP.NET Development Server/11.0.0.0

X-AspNet-Version:4.0.30319

X-AspNetMvc-Version:3.0

To see it in action for yourself , create a simple action like the one above , at first without the caching attribute and put a breakpoint in your controller action , you will note when you F5 the page , that it will hit the breakpoint every time.After decorating your action with the atttribute above , if you then run up your application , and F5 your page again , you can see that after the initial breakpoint being hit , the contents are cached and the breakpoint isnt hit again until your cache duration times out.

VaryByParam

The VaryByParam allows you to have different cached versions of the very same content. This property enables you to create different cached versions of the very same content for example when a query string parameter varies. By setting the VaryByParam property to “none” ,when the action is invoked, the same cached version of the action is returned i.e. any query string parameters are ignored , so usually if we have an action for a particular id , we'd want this to be cached based on the id , so we dont get the same results back.

If we have a number of params , and we want them all to be noted in the cache , we can either specific them semi-colon seperated list, or use the * in the VaryByParam value. E.G in the action which populates a grid below , we dont want the paging , sort and id queryparams to be ignored.

[OutputCache(Duration = 1, VaryByParam = "*")]

public ActionResult Index(int accountId, string page, string sort, string sortdir)

{

///code to get all accounts

return PartialView("_AccountsList", data);

}

File upload in MVC3/4

Those new to MVC or coming from classic ASP.NET might be a little daunted when first tasked with uploading a file in MVC , as there's no concept of the fileupload control (or any server side control for that matter)?

Thanks to Darin Dimitrov for the great example here:

Your controller

public class HomeController : Controller
{
// This action renders the form
public ActionResult Index()
{
return View();
}
// This action handles the form POST and the upload
[HttpPost]
public ActionResult Index(HttpPostedFileBase file)
{
// Verify that the user selected a file
if (file != null && file.ContentLength > 0)
{
// extract only the fielname
var fileName = Path.GetFileName(file.FileName);
// store the file inside ~/App_Data/uploads folder
var path = Path.Combine(Server.MapPath("~/App_Data/uploads"), fileName);
file.SaveAs(path);
}
// redirect back to the index action to show the form once again
return RedirectToAction("Index");
}
}

The view

@using (Html.BeginForm("Index", "Home", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
<input type="file" name="file" />
<input type="submit" value="OK" />
}