October | 2013 | Jamie Dixon's Home

A tale of two web hosting companies

October 29, 2013 Leave a comment

So as a Microsoft duh-veloper, I spend most of my time in the Microsoft stack, drinking from the fire hoses that stretches across the country from Redmond. Recently, I had an experience that made me want to turn off the hose for one of their products.

I signed up for Azure last year with a trial account so I could participate in Rock,Paper, Azure. I managed to get some of my co-workers to signup also and we had a good time competing against each other. I then canceled the subscription once the contest was over. A couple of months later, I spun up a new instance of Azure for Open Data day – trying to convince people to use Azure to host their data and expose public data to the rest of the world. The problem was that since I used my same credit card to sign up, I could not use the free 90 day trial, so I signed up for a pay-as-you-go one. After Open Data Day was over, I took down the site. Finally, at Tech Ed I met some people who were wondering about the cloud so I spun up an instance of Azure and Team Foundation Service so they can see if in action. After Tech Ed, I spun down that sight.

Meanwhile, each month, Azure was generating a service charge for a site that was not active. When I realized it (about 4 months later), I emailed the Azure team and asked that they refund the money because:

1) I was not using any site for anything real and the traffic logs confirm that

2) I was actually doing grass-root marketing for them.

Their response? No way! Perhaps it was because they had earnings coming up and my couple of hundred of dollars had a material impact on the 80.37 Billion in annual revenue they reported – I never under estimate the power of compound interest. In any event, I appealed the decision to the manager and his/her response?

I then hit up our local developer evangelist. He took a look and and got no where too (and I thought the DE were like the political commissioners/Darth Vaders and could bend the bureaucracy with their mind powers).

In any event, it was all right there – I should have turned off the site completely and I was at fault for not watching my account (and credit card statement) closely. Fair enough, I made the mistake and really have no one to blame but myself. I can already hear Rob Seder telling me that I could sign up for biz spark so I wouldn’t have been charged – but I guess I am more annoyed on how Microsoft treats the developers than how I could have avoided the fees.

I contrast this experience with another one I had this week with WinHost. I was running a site for a local group when the renewal came up. The group was done so the site was coming down – I put it on my life’s //TODO list to cancel the site. By the time I got to it – the site had renewed and the card had been charged. I immediately emailed their support and within 20 minutes, I had this in my inbox:

The thing is, WinHost didn’t have to refund the money – and they did anyway:

So the conclusions I draw are:

1) I am not going to recommend Azure for side-development to other devs and companies. It is a great platform – but it sure seems like Microsoft has lost its way in how it treats developers who use their technologies.

2) WinHost is awesome and I will continue to use them for web site and web Service hosting – and any new sites I do I will start on Win Host.

Filed under Web Hosting

Self-Referencing Keys Gotcha in EF

October 22, 2013 Leave a comment

Looking at the Employee table in Northwind, there is a self-referencing key on the ‘ReportsTo’ field

When a series of new employees are created, you might run into problems trying to commit those changes all at once. For example:

static void Main(string[] args)
{
    Console.WriteLine("Start");
 
    using (NorthwindEntities entities = new NorthwindEntities())
    {
        Employee employee1 = new Employee();
        employee1.FirstName = "Test";
        employee1.LastName = "Employee1";
        entities.Employees.Add(employee1);
 
        Employee employee2 = new Employee();
        employee2.FirstName = "Test";
        employee2.LastName = "Employee2";
        employee2.ReportsTo = employee1.EmployeeID;
        entities.Employees.Add(employee2);
 
        entities.SaveChanges();
    }
 
    Console.WriteLine("-Stop-");
    Console.ReadKey();
}

When you run this, you get this kind of exception:

The reason is that the PK of the 1st employee is 0 and the PK of the second employee is ….. 0. Since both are created on the client and have not had the ‘real’ primary key assigned by the database, the FK gets confused because there are 2 Primary Keys with the same value. And according to these calculations, that is impossible.

The way to fix this problem is to move the SaveChanges() to after each add like this:

using (NorthwindEntities entities = new NorthwindEntities())
{
    Employee employee1 = new Employee();
    employee1.FirstName = "Test";
    employee1.LastName = "Employee1";
    entities.Employees.Add(employee1);
    entities.SaveChanges();
 
    Employee employee2 = new Employee();
    employee2.FirstName = "Test";
    employee2.LastName = "Employee2";
    entities.Employees.Add(employee2);
    employee2.ReportsTo = employee1.EmployeeID;
    entities.SaveChanges();
 
}

Or to not associate the FK until the 1st bulk commit like this;

using (NorthwindEntities entities = new NorthwindEntities())
{
    Employee employee1 = new Employee();
    employee1.FirstName = "Test";
    employee1.LastName = "Employee1";
    entities.Employees.Add(employee1);
 
    Employee employee2 = new Employee();
    employee2.FirstName = "Test";
    employee2.LastName = "Employee2";
    entities.Employees.Add(employee2);
    entities.SaveChanges();
 
    employee2.ReportsTo = employee1.EmployeeID;
    entities.SaveChanges();
 
}

Filed under Entity Frameworks

Switch Databases Using EF: Part Deux

October 15, 2013 Leave a comment

Consider you are a company where you want to keep each of your customer’s data in its own database on the same server. Each of the databases has the identical schema. For example:

In the Data Access Layer, you are using Entity Framework and you want to move between databases at run time. I blogged about one possible solution to this problem here, but I was thinking about this some more and I have a different (better?) idea.

The first thing to realize is that EF does not make this easy. There is not a Contxext.ChangeDatabase(String) method and the constructor does not allow to pass in a connection string. This tight-coupling smells of poor design, but fortunately this is not insurmountable.

The first step is to create a Model (NorthwindModel in this case). When you inspect the context, you can see that Microsoft made the entities a partial class

So you can add a class to your project like so:

public partial class NorthwindEntities
{
    public NorthwindEntities(String connectionString)
    {
        base.Database.Connection.ConnectionString = connectionString;
    }
 
}

Then, in your consuming class, you can create a method like this:

internal static String CreateConnectionStringWithCustomDatabase(String baseConnectionString, String database)
{
    SqlConnectionStringBuilder connectionStringBuilder = new SqlConnectionStringBuilder(baseConnectionString);
    connectionStringBuilder.InitialCatalog = database;
    return connectionStringBuilder.ToString();
}

And then you can switch databases. Just pass in the default connection string and the new database name like so:

static void Main(string[] args)
{
    Console.WriteLine("Start");
    String defaultConnectionString = "data source=DIXON12;initial catalog=TBD;integrated security=True;MultipleActiveResultSets=True";
    String actualConnectionString = CreateConnectionStringWithCustomDatabase(defaultConnectionString, "Northwind");
 
    using (NorthwindEntities entities = new NorthwindEntities(actualConnectionString))
    {
        foreach (var product in entities.Products)
        {
            Console.WriteLine(product.ProductName);
        }
    }
 
    Console.WriteLine("-End-");
    Console.ReadKey();
 
}

And you can change databases on the fly:

The ’gotcha’ to realize is that Entity Framework requires that you have a default value in the app/web.config file. If not, you will get this exception:

This smells like too much coupling, but that is a common theme with EF. So make sure you have a default EF connection string in the .config – even if you don’t even use it.

Filed under Entity Frameworks

F# and C#: The cross-over syntax

October 8, 2013 Leave a comment

As part of my F# presentation to the TRINUG code camp, I did Question #1 of Project Euler. I started with a typical way a C# programmer might approach it: using mutable variables and looping. Something like this:

public static Int32 TryOne()
{
    List<Int32> selectedNumbers = new List<int>();
    for (int number = 0; number < 1000; number++)
    {
        if (number % 3 == 0)
        {
            selectedNumbers.Add(number);
        }
 
        if (number % 5 == 0)
        {
            if (!selectedNumbers.Contains(number))
            {
                selectedNumbers.Add(number);
            }
        }
    }
 
    Int32 total = 0;
    foreach (Int32 number in selectedNumbers)
    {
        total += number;
    }
 
    return total;
}

I then demonstrated they way a typical F# might approach the problem:

open System
 
let tryOne = [1..1000]
                    |> Seq.filter(fun number -> (number%3 = 0 || number%5 = 0))
                    |> Seq.sum

There are some differences worth noting. The first is the terseness of F# and less “noise” of curley-braces and semi-colons. The second is that the F# is more readable than the C# – assuming the person reading the code is not steeped in the java/C++/C# syntax. Finally, there are less chance for bugs in the F# code. In the C# code, there is a chance that selectedNumbers varaible might be altered and the total variable might be altered – esp. when doing the program in a multi-threaded manner.

Next, a more advanced C# developer might use Linq or Lambdas to write the answer like this:

public static Int32 TryTwo()
{
    var total = Enumerable.Range(0, 1000)
                        .Where(number => (number % 3 == 0) || (number % 5 == 0))
                        .Sum();
    return total;
}

The similarity between this C# code and the F# code is striking. The biggest difference is that the OO syntax makes the functions a part of the object being acted upon while the functional syntax makes the functions a part of a separate construct. This change in perspective is the only real difference – and I am noticing that the more you look at code via the functional way, more mental doors are opened when solving a problem…

Filed under F#

Relative Speed: F# v C# v VB.NET

October 1, 2013 2 Comments

(Spoiler alert: F# is faster – by alot)

As part of my presentation on F# which I hope to show at CodeCamp 2013, I did a quick speed test among C#, VB.NET, and F#. I thought about Dr. Evil and how he tried to ransom the UN for “One Million Dollars” and I thought about how the Federal Reserve is creating money from nothing to the tune of $40 Million a month via QE3 – so I built a quick app that does the exact same thing as the Federal Reserve does (except mine has unit tests, theirs probably does not).

I created a class for a Dollar bill (C#, VB, F#):

public class Dollar
{
    public Int32 Id { get; set; }
    public String SerialNumber { get; set; }
    public Int32 FederalReserveDistrict { get; set; }
    public Int32 SeriesDate { get; set; }
    public String Signature { get; set; }
}

Public Class Dollar
    Public Property Id As Int32
    Public Property SerialNumber As String
    Public Property FederalReserveDistrictNumber As Int32
    Public Property SeriesDate As Int32
    Public Property Signature As String
End Class

type dollar =
    {Id: int;
     SerialNumber: string;
     federalReserveDistrict: int;
     seriesDate: int;
     signature: string}

I then implemented the same algorithm that the Federal reserve uses (C#, VB, F#):

public List<Dollar> GetDollars(Int32 numberOfDollars)
{
    List<Dollar> dollars = new List<Dollar>();
    Dollar currentDollar = null;
    Random random = new Random();
    for (int i = 0; i < numberOfDollars; i++)
    {
        currentDollar = new Dollar();
        currentDollar.FederalReserveDistrict = random.Next(1, 13);
        currentDollar.Id = i;
 
        String serialNumber = String.Empty;
        for (int j = 0; j < 9; j++)
        {
            serialNumber += random.Next(0, 9).ToString();
        }
        currentDollar.SerialNumber = serialNumber;
        currentDollar.SeriesDate = 2000 + random.Next(0, 10);
        dollars.Add(currentDollar);
    }
    return dollars;
}

Public Function GetDollars(ByVal numberOfDollars As Int32) As List(Of Dollar)
    Dim dollars As New List(Of Dollar)()
    Dim currentDollar As Dollar = Nothing
    Dim random As New Random()
    For dollarIndex As Integer = 0 To numberOfDollars – 1
        currentDollar = New Dollar()
        currentDollar.FederalReserveDistrictNumber = random.Next(1, 13)
        currentDollar.Id = dollarIndex
 
        Dim serialNumer As String = String.Empty
        For serialNumberIndex As Integer = 0 To 9
            serialNumer += random.Next(0, 9).ToString()
        Next
 
        currentDollar.SerialNumber = serialNumer
        currentDollar.SeriesDate = 2000 + random.Next(0, 10)
        dollars.Add(currentDollar)
    Next
    Return dollars
End Function

type dollarProvider() =
    let randomNumberGenerator = new System.Random()
    let createSerialNumber =
        List.init 9 (fun _ -> randomNumberGenerator.Next(0,9))
                                    |> Seq.map string
                                    |> String.concat ""
    let createDollar id =
        let returnDollar = {Id=id;
            SerialNumber= createSerialNumber ;
            federalReserveDistrict=randomNumberGenerator.Next(0,13);
            seriesDate=2000+randomNumberGenerator.Next(0,9);
            signature=""}
        returnDollar
 
    member this.GetDollars (numberOfDollars:int) =
        List.init numberOfDollars (fun index -> createDollar index)

I then created a WPF I with the following XAML:

<Grid>
    <Button Content="Run C#" Height="32" HorizontalAlignment="Left" Margin="12,97,0,0" Name="CSharpButton" VerticalAlignment="Top" Width="95" Click="CSharpButton_Click" />
    <TextBox Height="20" HorizontalAlignment="Left" Margin="12,150,0,0" Name="CSharpResultsTextBox" VerticalAlignment="Top" Width="95" />
    <Button Content="Run VB" Height="29" HorizontalAlignment="Left" Margin="120,99,0,0" Name="RunVBButton" VerticalAlignment="Top" Width="99" Click="RunVBButton_Click" />
    <TextBox Height="19" HorizontalAlignment="Left" Margin="117,150,0,0" Name="VBResultsTextBox" VerticalAlignment="Top" Width="102" />
    <Button Content="Run F#" Height="28" HorizontalAlignment="Right" Margin="0,99,162,0" Name="RunFSharpButton" VerticalAlignment="Top" Width="105" Click="RunFSharpButton_Click" />
    <TextBox Height="22" HorizontalAlignment="Left" Margin="239,147,0,0" Name="FSharpResultsTextBox" VerticalAlignment="Top" Width="102" />
    <Label Content="Number Of Dollars" Height="30" HorizontalAlignment="Left" Margin="12,18,0,0" Name="label1" VerticalAlignment="Top" Width="115" />
            <TextBox Height="24" HorizontalAlignment="Left" Margin="126,22,0,0" Name="DollarsTextBox" VerticalAlignment="Top" Width="115" Text="1000000" />
</Grid>

and Code Behind

private void CSharpButton_Click(object sender, RoutedEventArgs e)
{
    Stopwatch stopWatch = new Stopwatch();
    stopWatch.Start();
    CS.DollarProvider provider = new CS.DollarProvider();
    Int32 numberOfDollars = Int32.Parse(this.DollarsTextBox.Text);
    provider.GetDollars(numberOfDollars);
    stopWatch.Stop();
 
    this.CSharpResultsTextBox.Text = stopWatch.Elapsed.TotalSeconds.ToString() + " seconds";
 
}
 
private void RunVBButton_Click(object sender, RoutedEventArgs e)
{
    Stopwatch stopWatch = new Stopwatch();
    stopWatch.Start();
    VB.DollarProvider provider = new VB.DollarProvider();
    Int32 numberOfDollars = Int32.Parse(this.DollarsTextBox.Text);
    provider.GetDollars(numberOfDollars);
    stopWatch.Stop();
 
    this.VBResultsTextBox.Text = stopWatch.Elapsed.TotalSeconds.ToString() + " seconds";
 
}
 
private void RunFSharpButton_Click(object sender, RoutedEventArgs e)
{
    Stopwatch stopWatch = new Stopwatch();
    stopWatch.Start();
    FS.dollarProvider provider = new FS.dollarProvider();
    Int32 numberOfDollars = Int32.Parse(this.DollarsTextBox.Text);
    provider.GetDollars(numberOfDollars);
    stopWatch.Stop();
 
    this.FSharpResultsTextBox.Text = stopWatch.Elapsed.TotalSeconds.ToString() + " seconds";
}

And the results are pretty revealing:

I acknowledge that you can jerry rig C# to improve performance – esp using Pointers and the GOTO statement. This exercise was to show performance doing the commonly-accepted way to solve a problem in each language (without FxCOP yelling at you). It was not designed to see how clever you can get with C# to match the performance of the F# implementation. As Rob Seder said “You can also bang in a screw by turning around the screwdriver and whacking away.” If you need speed, F# is the best tool for the job.

Filed under F#

Handling images in WebApi

October 1, 2013 15 Comments

I am digging into WebApi (v1) and one of the issues I was facing was images – specifically how to handle images. I spent a fair amount of time researching the possibilities over the last couple of days and this is what I think I think.

1) You can include your image in your JSON payload like this:

public class Person
{
    public Int32 PersonId { get; set; }
    public String FirstName { get; set; }
    public byte[] Image { get; set; }
}

or you can include the imageUri in your JSON payload like this:

public class Person
{
    public Int32 PersonId { get; set; }
    public String FirstName { get; set; }
    public String ImageUri { get; set; }
}

The advantage of the former is that you can make 1 POST or GET call and get all of the data. The disadvantages are that the image gets serialized into a large size and your service can get bogged down processing images when the rest of the payload is very small.

The advantage of the later is that you can separate the image into its own location – in fact not even use a Controller, and the processing is snappy-pappy. The downside is that you need to make 2 GETs and POSTs for any given person (in this example). For the POST, there is the additional factor that you have to wait for the 1st post to complete so you can get some kind of association key returned so that both POSTs can be associated together I was talking to fellow TRINUG member Ian Hoppes about problem and he came up with a great idea – have the client generate a GUID and then push both POSTs at the same time.

In any event, if you separate the payload into two POSTS, you need a way of handling the image alone. In WebApi V1, there seems to be 3 different ways you can do this:

A Controller
A Handler
A Formatter

I wasn’t sure what was the <right> answer so I posted this question to stack overflow – and no one answered it (at the time of this writing). Left to my own devices, I decided to use an image controller so that the API has consistent implementation.

I newed up an Image Controller and added 3 methods: GET, POST, and DELETE. The GET was pretty straight foreward (I used a Int32 on the parameter because I haven’t implemented the GUID yet):

public HttpResponseMessage Get(int id)
{
    var result = new HttpResponseMessage(HttpStatusCode.OK);
    String filePath = HostingEnvironment.MapPath("~/Images/HT.jpg");
    FileStream fileStream = new FileStream(filePath, FileMode.Open);
    Image image = Image.FromStream(fileStream);
    MemoryStream memoryStream = new MemoryStream();
    image.Save(memoryStream, ImageFormat.Jpeg);
    result.Content = new ByteArrayContent(memoryStream.ToArray());
    result.Content.Headers.ContentType = new MediaTypeHeaderValue("image/jpeg");
 
    return result;
}

The DELETE was event easier:

public void Delete(int id)
{
    String filePath = HostingEnvironment.MapPath("~/Images/HT.jpg");
    File.Delete(filePath);
}

The POST, not so easy. My first attempt was to read the steam and push it into an Image:

public void Post()
{
    var result = new HttpResponseMessage(HttpStatusCode.OK);
    if (Request.Content.IsMimeMultipartContent())
    {
        StreamContent content = (StreamContent)Request.Content;
        Task<Stream> task = content.ReadAsStreamAsync();
        Stream readOnlyStream = task.Result;
        Byte[] buffer = new Byte[readOnlyStream.Length];
        readOnlyStream.Read(buffer, 0, buffer.Length);
        MemoryStream memoryStream = new MemoryStream(buffer);
        Image image = Image.FromStream(memoryStream);
    }
    else
    {
        throw new HttpResponseException(Request.CreateResponse(HttpStatusCode.NotAcceptable, "This request is not properly formatted"));
    }
}

No dice, because the stream includes things other than the image binrary. My second attempt was to use the MutlipartFormDataStreamProvider (which is the most popular way apparently) like so:

public Task<HttpResponseMessage> Post(int id)
{
    if (!Request.Content.IsMimeMultipartContent())
    {
        throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
    }
 
    string root = HttpContext.Current.Server.MapPath("~/Images");
    var provider = new MultipartFormDataStreamProvider(root);
 
    var task = Request.Content.ReadAsMultipartAsync(provider).
        ContinueWith<HttpResponseMessage>(t =>
        {
            if (t.IsFaulted || t.IsCanceled)
            {
                Request.CreateErrorResponse(HttpStatusCode.InternalServerError, t.Exception);
            }
 
            foreach (MultipartFileData file in provider.FileData)
            {
                //Trace.WriteLine(file.Headers.ContentDisposition.FileName);
                //Trace.WriteLine("Server file path: " + file.LocalFileName);
            }
            return Request.CreateResponse(HttpStatusCode.OK);
        });
 
    return task;
}

I don’t like this because I am writing to disk first – and I don’t need to use the file system – in fact, it might be locked down in some scenarios. So finally, I cobbled together some posts and found a way to read the parsed stream and create an image without using disk:

public HttpResponseMessage Post()
{
    var result = new HttpResponseMessage(HttpStatusCode.OK);
    if (Request.Content.IsMimeMultipartContent())
    {
        Request.Content.ReadAsMultipartAsync<MultipartMemoryStreamProvider>(new MultipartMemoryStreamProvider()).ContinueWith((task) =>
        {
            MultipartMemoryStreamProvider provider = task.Result;
            foreach (HttpContent content in provider.Contents)
            {
                Stream stream = content.ReadAsStreamAsync().Result;
                Image image = Image.FromStream(stream);
                var testName = content.Headers.ContentDisposition.Name;
                String filePath = HostingEnvironment.MapPath("~/Images/");
                String[] headerValues = (String[])Request.Headers.GetValues("UniqueId");
                String fileName = headerValues[0] + ".jpg";
                String fullPath = Path.Combine(filePath, fileName);
                image.Save(fullPath);
            }
        });
        return result;
    }
    else
    {
        throw new HttpResponseException(Request.CreateResponse(HttpStatusCode.NotAcceptable, "This request is not properly formatted"));
    }
 
 
}

Note that I am using a disk right now on the POST and GET but I am going to swap it out with Azure Blob Storage. That way I can just create the image and push it over to Azure without my local disk being used at all.

Sure enough, this works like a champ. The GET

and the POST (using Fiddler – you have to use the most recent Fiddler so you get the [Upload File] link):

Another note is that I am pushing the UniqueID of the image in the request header – not in the content’s header.

This works:

(String[])Request.Headers.GetValues("UniqueId");

This does not:

var testName = content.Headers.GetValues("UniqueId");

Filed under WebApi

Jamie Dixon's Home

A tale of two web hosting companies

Self-Referencing Keys Gotcha in EF

Switch Databases Using EF: Part Deux

F# and C#: The cross-over syntax

Relative Speed: F# v C# v VB.NET

Handling images in WebApi

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