Itai Goldstein

SkyDrive Explorer

itai — Wed, 03 Feb 2010 13:54:56 GMT

The Microsoft SkyDrive is a very useful storage service. it gives you 25 GB of storage where you can store any files you’d like when each file weigh no more than 50 MB.

If you decide to use SkyDrive (which I highly recommend), check out SkyDrive Explorer – this tool improves the SkyDrive experience and allows using SkyDrive similarly as using another drive on your computer.

Here’s where you can download it from: SkyDrive Explorer download.

Enjoy,

Itai

IIS SEO Toolkit Beta Released

itai — Thu, 04 Jun 2009 03:39:33 GMT

Microsoft are shipping today a new tool – IIS Search Engine Optimization Toolkit – which helps developers to analyze their site from SEO prospective.

When a site is SEO Optimized – it basically means that this site is designed in a way that search engines can easily relate it to specific keywords so it will appear high on the search engine results.

The tool that Microsoft are releasing today helps the developers identify mistakes as broken links, poorly chosen title, description and more.

Read more about it at Scott Guthrie excellent blog post here: IIS Search Engine Optimization Toolkit post

How To: Font Embedding In Silverlight

itai — Sun, 10 May 2009 18:19:04 GMT

Silverlight includes nine basic core fonts (these fonts can be rendered correctly on any browser and operating system Silverlight supports):

Arial
Arial Black
Comic Sans MS
Courier New
Georgia
Lucida Grande / Lucida Sans Unicode
Times New Roman
Trebuchet MS
Verdana

But what can you do when you like to use another font which is not included in the core fonts list?

The answer is embedding the desired font in your Silverlight application:

Add the font file to your application and set the Build Action to Resource:
Set the FontFamily property in the following format: FontFileName#FontName

<TextBlock Text="This is Calibri Font" 
           FontFamily="CALIBRI.TTF#Calibri" 
           FontSize="20">            
</TextBlock>

Or you can achieve the same effect in the code behind:

StreamResourceInfo sri = Application.GetResourceStream(
    new Uri("SilverlightApplication1;component/CALIBRI.TTF", 
        UriKind.Relative));
TextBlock1.FontSource = new FontSource(sri.Stream);
TextBlock1.FontFamily = new FontFamily("Calibri");

And here’s the result:

Hope you find it useful.

And the Emmy goes to… Silverlight!

itai — Fri, 08 May 2009 03:09:07 GMT

NBC Olympics wins an Emmy for its online coverage of 2008 Summer Olympics where Silverlight took a major part in “Outstanding New Approaches Sport Event Coverage”.

This should boost up Silverlight reputation..

Azure Design Patterns Site

itai — Tue, 05 May 2009 19:58:23 GMT

I came across this Azure Design Patterns site which I found very interesting and worth sharing.

Cheat Sheets

itai — Tue, 31 Mar 2009 14:03:37 GMT

This might come handy for some of you out there: cheat sheets for developers and students.

Hope you’ll find it useful.

Generating SQL Server DB scripts

itai — Thu, 26 Mar 2009 18:25:57 GMT

This solution is probably known to a lot of you out there, but for the ones who don’t, here is the solution in a Step-By-Step tutorial:

In SQL Server Management Studio right click on one of the databases on your Object Explorer, and choose Tasks->Generate Scripts…:

Then you’ll be introduced with the SQL Server Scripts Wizard:

Next, you need to choose the database you would like to generate scripts for, in this step you can choose whether to script all objects in your database, or you can set the ones you want in a latter step:

Now you need to choose your script options:

In the following steps you need to configure which object types you would like to script, and choose the specific objects (unless you decided to check the “Script all objects in the selected database” option):

The Object types you want to script:

And the objects:In the last step, you need to choose where to output the script to:

That’s it.

Hope you’ll find it useful.

Configuring AJAX Extensions In SharePoint

itai — Mon, 23 Mar 2009 16:53:36 GMT

Using SmartPart in SharePoint can reduce web parts development time.

The SmartPart install document includes instructions on configuring AJAX Extensions on SharePoint website configuration file, but it lacks 2 issues I’ve encountered while enabling SmartPart on my SharePoint website:

This is pretty straight forward – if you’re using a more advanced version of the AJAX extensions – you should update its full assembly name:
```
Assembly="ReturnOfSmartPart, Version=1.3.0.0, Culture=neutral, PublicKeyToken=9f4da00116c38ec5"
```

Under runtime->assemblyBinding tags add a dependent assembly tag:

<dependentAssembly>
  <assemblyIdentity name="System.Web.Extensions" publicKeyToken="31bf3856ad364e35" />
  <bindingRedirect oldVersion="1.0.0.0-1.1.0.0" newVersion="3.5.0.0" />
</dependentAssembly>

Hope you’ll find it useful.

How To: Implement HMAC Authentication On a RESTful WCF Service

itai — Sun, 22 Feb 2009 21:21:00 GMT

There are several approaches in implementing authentication in RESTful WCF services. Using SSL and Digest Authentication are two options, while in this post I would like to demonstrate another approach which uses HMAC (Hash Message Authentication Code) in order to achieve both message authentication and integrity.

In this approach the server provides the client an ID and a secret key through some technique (e.g. sending an email containing the ID and the secret key) which will be used by the client to sign all his requests.

A secret key can be generated in the following way:

byte[] secretkey = new Byte[64];
RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
rng.GetBytes(secretkey);

This post will not cover what is a RESTful service and how should we implement all it’s properties in WCF, for this purpose you can refer to this great article which I used in my research prior to this post.

In our example the service will provide specific user’s bookmarks to its consumer. In order to consume this service, a requester must provide some hashed message (in our case – the request Uri encrypted with the secret key) in the request header authorization property (different implementations of the client would be provided in future posts).

So without further ado's, this is the service contract method definition:

[WebGet(UriTemplate = "users/{username}/bookmarks?tag={tag}")]
[OperationContract]
Bookmarks GetUserBookmarks(string username, string tag);

The contract enforces us to use the specified Uri template which implies that for a specific username (the requested user) and specific tag filter, the requester will be provided with a bookmarks list matching this criteria.

Here is the service method implementation:

public Bookmarks GetUserBookmarks(string username, string tag)
{
    WebOperationContext context = WebOperationContext.Current;
    OutgoingWebResponseContext outgoingResponseContext =
        context.OutgoingResponse;                       

    bool isUserAuthenticated = IsUserAuthenticated(username);
    if (isUserAuthenticated == false)
    {
        outgoingResponseContext.StatusCode = HttpStatusCode.Unauthorized;
        return null;
    }
    
    outgoingResponseContext.StatusCode = HttpStatusCode.OK;
    Bookmarks bookmarks = 
        new Bookmarks(BookmarksProvider.GetUserBookmarks(username, tag));

    return bookmarks;
}

The simple implementation I used here suggests that the request is being checked for its user’s authentication: if the authentication fails, the requester will be responded with Unauthorized HTTP status code (401) and no bookmarks. If the authentication succeeds – the bookmarks list is provided along with OK HTTP status code (200).

I’ve skipped the BookmarksProvider.GetUserBookmarks method implementation due to it’s irrelevancy for this post subject.

Here is my implementation for the IsUserAuthenticated method:

private bool IsUserAuthenticated(string username)
{
    WebOperationContext context = WebOperationContext.Current;
    IncomingWebRequestContext incomingRequestContext =
        context.IncomingRequest;

    string requestUri =
        incomingRequestContext.UriTemplateMatch.RequestUri.ToString();
    string authorizationHeader =
        incomingRequestContext.Headers[HttpRequestHeader.Authorization];

    string authenticationToekn = 
        string.Format("{1}{0}{2}", 
            Delimeters.FirstClassDelimeter, 
            authorizationHeader, 
            requestUri);

    byte[] userKey = GetUserKey(username);
    bool isValidHash = Authentication.ValidateHash(
        userKey,
        authenticationToekn, 
        Delimeters.FirstClassDelimeter, 
        UTF8Encoding.UTF8);

    return isValidHash;
}

This method composes an authentication token (this is a pure implementation step – it is up to the server to decide it’s protocol – and up to the client to obey in order to consume..) from the request Uri and the hashed authorization header. Then the authentication token is being validated along with the current requester secret key (fetched by the GetUserKey method) through the Authentication.ValidateHash method:

public static bool ValidateHash(byte[] key, 
    string message, string delimeter, Encoding encoding)
{
    HMACMD5 hmacMD5 = new HMACMD5(key);
    string[] messageParts =
        message.Split(new string[] { delimeter },
        StringSplitOptions.RemoveEmptyEntries);

    if (messageParts == null || messageParts.Length < 2)
    {
        return false;
    }

    string encodedText = messageParts[0];
    string text = messageParts[1];
    byte[] textBytes = encoding.GetBytes(text);
    byte[] computedHash = hmacMD5.ComputeHash(textBytes);
    string computedHashString = Convert.ToBase64String(computedHash);
    return encodedText.Equals(computedHashString);
}

In the validation method, the authentication token is being split to the message and hashed message parts – in our case, it’s the request Uri and the request Uri hashed using the requester’s secret key. After the parts are split, the secret key is being used to generate the hashed message (using the HMACMD5 class) again in order to be compared to the received hashed message. If the hashed messages are equal then the authentication is ok, otherwise it is invalid.

There are several ways to consume this service. In this post I’ll go over one of them in which a console application consumes our service:

byte[] key = GetUserKey();
string uri = "http://localhost:4609/ServiceHost/BookmarksService.svc/users/itai/bookmarks?tag=News";
HttpWebRequest request = WebRequest.Create(uri) as HttpWebRequest;
string encodedUri = Authentication.EncodeText(key, uri, UTF8Encoding.UTF8);
request.Headers[HttpRequestHeader.Authorization] = encodedUri;
HttpWebResponse response = request.GetResponse() as HttpWebResponse;
Stream bookmarksStream = response.GetResponseStream();
StreamReader reader = new StreamReader(bookmarksStream);
string str = reader.ReadToEnd();
reader.Close();
bookmarksStream.Close();

As you can see for yourself, this client is rather simple: prepare the request object using service Uri and define the authorization header using the client secret key to hash the message (in our case it is the request Uri), then send the request and parse the response (XML formatted).

Here is Authentication.EncodeText method implementation:

public static string EncodeText(byte[] key, string text, Encoding encoding)
{
    HMACMD5 hmacMD5 = new HMACMD5(key);
    byte[] textBytes = encoding.GetBytes(text);
    byte[] encodedTextBytes =
        hmacMD5.ComputeHash(textBytes);
    string encodedText =
        Convert.ToBase64String(encodedTextBytes);
    return encodedText;
}

And here are our client results:

Summary

In this post I’ve implemented a RESTful WCF service which is protected by HMAC authentication token which is being passed in the service request header by a simple service consumer.

In my upcoming posts, I’ll review another different client implementations – stay tuned..

Hope you’ll find it useful.

References:

A Guide to Designing and Building RESTful Web Services with WCF 3.5

HMACMD5 at MSDN

Configuration shortcuts (or IntelliSense for configuration file)

itai — Wed, 18 Feb 2009 15:39:49 GMT

The configuration appSettings & connectionStrings sections are highly used in our daily application development.

<appSettings>
  <add key="ApplicationName" value="ConfigurationShortcutsSample"/>
</appSettings>

The way we usually access the values which are stored within these sections is through the ConfigurationManager class when we specify the section key string:

string applicationName
    = ConfigurationManager.AppSettings
        [AppSettingsKeys.ApplicationName];

This methodology could lead us developers to mistakes which can be detected only at runtime in case we mistyped the application setting key string.

I would like to offer another way of accessing these sections which will prevent us from mistyping the application setting key and even provide sort of IntelliSense.

In this way, we need to write a static class which will hold the keys for our configuration section keys in static properties:


public static class AppSettingsKeys
{
    public static string ApplicationName 
    { 
        get { return "ApplicationName"; } 
    }        
}

That’s it.. now we can access our configuration application settings keys with the help of our static class:

Summary

In this post I reviewed a way to have shortcuts to our configuration file appSettings & connectionStrings sections which can act as IntelliSense and prevent us from coding mistakes which can be detected only on runtime.

Hope you’ll find it useful.

Redirecting on a callback

itai — Wed, 11 Feb 2009 13:24:32 GMT

In one of my previous posts, I reviewed a way to handle client side events on the server side by using the Callback feature of ASP.NET 2.0.

But what about redirecting from the current page when you handle the client event?

You’ll find that it is not possible: “Response.Redirect cannot be called in a Page callback.” or “Server.Transfer cannot be called in a Page callback.” messages will appear in case you’ll use Response.Redirect or Server.Transfer operations

In order to redirect to another page at the end of your flow, you’ll have to do it in the client side callback handler which was defined at the ClientScriptManager.GetCallbackEventReference method:

Hope you’ll find it useful.

Improve your ASP.NET Website User Experience: Flush Down your partial Response

itai — Sun, 08 Feb 2009 13:46:28 GMT

There are times when your website page needs to do some heavy work on the server side and you don’t want your user to wait till the work is complete to get a response.

In these cases you can use the Response.Write & Response.Flush methods, and here is a short example (on the HTML source side):

        <% Response.Write("1st response..."); %>
        <% Response.Flush(); %>
        <% System.Threading.Thread.Sleep(2000); %>
        
        <% Response.Write("2nd response..."); %>
        <% Response.Flush(); %>
        <% System.Threading.Thread.Sleep(2000); %>
        
        <% Response.Write("3rd response..."); %>
        <% Response.Flush(); %>
        
        <% Response.Write("4th response..."); %>
        <% Response.Flush(); %>

When you’ll run this code, you’ll find that the page is loaded with “1st response…” message, after 2 more seconds, the “2nd response…” would popup, and after 2 more seconds, the last two messages would appear.

This means that we can show our website users some response while our server doing some work.

This will work also on the code-behind, but needs a little tweak..

    Response.Write("1st response...");
    Response.Flush();
    Response.Flush();
    System.Threading.Thread.Sleep(2000);
    Response.Write("2nd response...");
    Response.Flush();
    Response.Flush();
    System.Threading.Thread.Sleep(2000);
    Response.Write("3rd response...");
    Response.Flush();
    Response.Write("4th response...");
    Response.Flush();

You probably notice that each Response.Flush appear twice, this is not a mistake - The reason is that sometimes when “you have to use more than a handful of toilet paper, it’s best to flush twice”..

Hope you’ll find it useful.

Quince - User Experience Design patterns Exploration Tool

itai — Tue, 03 Feb 2009 21:41:06 GMT

There is no need to break your head each time you try to find the best way to design your application user interface in order to provide the best user experience to your application users.

You can check out the Infragistics Quince which is a User experience (UX) patterns exploration tool.

There are different ways to find the pattern you are looking for:

Here is exploring all patterns method:

And here is exploring by tag relations method:

And the pattern description screen is very intuitive:

You can check out this blog post, which introduces this tool.

Hope you’ll find it useful.

T-SQL Split function

itai — Sun, 01 Feb 2009 20:54:11 GMT

During one of the projects I worked on, I had to parse a text which was passed from the application in my T-SQL code. I found that T-SQL had no built-in string system function for this operation, which I find rather useful, especially in cases you need to perform some batch based operations (which helps accelerate your application performance by reducing round trips to the DB).

So I came up with the following solution:

CREATE FUNCTION [dbo].[Split]
(    
    @RowData NVARCHAR(MAX),
    @Delimeter NVARCHAR(MAX)
)
RETURNS @RtnValue TABLE 
(
    ID INT IDENTITY(1,1),
    Data NVARCHAR(MAX)
) 
AS
BEGIN 
    DECLARE @Iterator INT
    SET @Iterator = 1

    DECLARE @FoundIndex INT
    SET @FoundIndex = CHARINDEX(@Delimeter,@RowData)

    WHILE (@FoundIndex>0)
    BEGIN
        INSERT INTO @RtnValue (data)
        SELECT 
            Data = LTRIM(RTRIM(SUBSTRING(@RowData, 1, @FoundIndex - 1)))

        SET @RowData = SUBSTRING(@RowData,
                @FoundIndex + DATALENGTH(@Delimeter) / 2,
                LEN(@RowData))

        SET @Iterator = @Iterator + 1
        SET @FoundIndex = CHARINDEX(@Delimeter, @RowData)
    END
    
    INSERT INTO @RtnValue (Data)
    SELECT Data = LTRIM(RTRIM(@RowData))

    RETURN
END

Note that this implementation uses DATALENGTH function instead of the LEN function, and that is due to the fact that LEN doesn’t consider the leading spaces in the given string variable – this can harm the parsed result. Another difference between DATALENGTH and LEN is that DATALENGTH returns the result as the number of bytes used where LEN returns the result as number of characters, and that is the reason we should divide the DATALENGTH result with 2.

Here is an example of how to use the Split function:

DECLARE @Str NVARCHAR(MAX)
SELECT @Str = 'This#$#is#$#my#$#test'

SELECT *
FROM   [dbo].[Split] (@Str, '#$#')

And here are the results:

Summary

In this post I reviewed my implementation for T-SQL string Split function which you may find useful when parsing strings in T-SQL, especially in cases you would like to improve your application performance by doing some batch based operations.

Hope you’ll find it useful.

Transform List to List where T inherits from K

itai — Mon, 26 Jan 2009 02:02:00 GMT

Download ListExtension.cs file :

Sometimes it is useful to copy one list contents to another which its type is more general.

Let me emphasize my intent with a small example:

Let there be a Dog, Cat & a Mouse types which inherit from Animal type, and let there be some lists: List<Dog>, List<Cat> & List<Mouse> list that we would like to union to one List<Animal> list in order to perform an general operation on all of the animals objects.

Here’s an example of these classes implementation for clarifying purpose:

We can try adding the specific lists to the general list (e.g.: adding List<Dog> to List<Animal>):

Casting dogs list to List<Animal> is also not allowed.

So we need a way to transform the specific type list to its general type form, something like the following:

In order to enable us to perform the precedes we’ll use the Extension Method feature in .NET 3.5 to extend the List<T> type with the Transform method:

Note how the Transform method signature enforces T type to inherit from K type using the where keyword.

Summary

In this post I reviewed a way to transform one typed generic list List<T> to another typed generic list List<K> in case that the type T inherits from the type K and used Extension Method feature to add this capability to the List<T> class.

Hope you’ll find it useful.

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