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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘.NET’ Category

StackOverflow C# question: Slight confusion over reference types and value types in the C# spec

Posted by jpluimers on 2011/06/23

Recently there was a nice Slight confusion over reference types and value types in the C# spec on StackOverflow.

Summary:

When structs are value types, but interfaces are reference types, how can a struct implement an interface and still be a value type?

The answer is boxing: when a reference to a struct is needed, a reference object is automatically created, and the value of the struct is box-wrapped into it.

This automatic boxing is really nice, but be aware that when frequently doing this, it can have a huge performance impact.

Thanks Abhina Basu for blogging about boxing structs having interfaces, and the many volunteers on StackOverflow explaining about boxing.

–jeroen

Posted in .NET, C#, Development | Leave a Comment »

.NET WPF Databinding to Collection Properties » Danny Thorpe

Posted by jpluimers on 2011/06/22

Danny Thorpe recently wrote a very nice post on via Databinding Collection Properties in WPF that sometimes fail without warning.

The short summary is that this fails without warning when binding to properties that do not explicitly implement the IList interface, for instance when binding to a collection that supports only IEnumerable (because of yield return) or IList<T> (for instance when binding to a Dictionary<TKey, TValue>.Values, which implements IList<T>, but not IList).

Thanks Danny for blogging about this (he explains it way better than I can), and putting a warning that the workaround Dictionary<TKey, TValue>.Values.ToList() potentially can have a big impact on memory consumption.

Life would be so much easier if WPF could bind to IEnumerable or IList<T> :)

–jeroen

via: Databinding Collection Properties » Danny Thorpe.

Posted in .NET, Development, Software Development, WPF | 2 Comments »

c# – Generics and nullable type – Stack Overflow

Posted by jpluimers on 2011/06/14

A while ago, I needed some generic way of parsing data that could result instancef of both regular ordinal and nullable ordinal types.

Luckily there was a nice question about this on StackOverflow, of which I liked this answer (source code below) much more than the accepted answer: concise, elegant, period.

    public static T? Parse(this string text) where T: struct
    {
        object o = null;
        try
        {
            var ttype = typeof(T);
            if (ttype.IsEnum)
            {
                T n = default(T);
                if (Enum.TryParse(text, true, out n))
                    return n;
            }
            else
                o = Convert.ChangeType(text, ttype);
        }
        catch { }

        if (o == null)
            return new Nullable();

        return new Nullable((T)o);
    }

–jeroen

Posted in .NET, C#, C# 2.0, C# 3.0, C# 4.0, Development, Software Development | 1 Comment »

Delphi Win32 talking to .net – Different WSDL ASMX,WCF web-services – Stack Overflow

Posted by jpluimers on 2011/05/31

An interesting question on Stackoverflow.com: .net – Different WSDL ASMX,WCF web-services – Stack Overflow.

The answer is simple when you know it: flatten the WSDL that comes from WCF.

Note that Delphi Win32 is not the only client having these issues, as Elton Stoneman shows on his blog and the WCFExtras toolkit for WCF that allows for single WSDL export.

–jeroen

Posted in .NET, Delphi, Development, Software Development | Leave a Comment »

Visual Studio 2010/2008/2005 – how can i check who has a specific file checked out in tfs? (via: Stack Overflow)

Posted by jpluimers on 2011/05/26

When you are using Team Foundation System (TFS) for version control, the project manager sometimes shows a file as being checked out by someone else, but it doesn’t show who that someone else is.

The reason is that the Project Manager only has generic knowledge about version control systems. However, the Source Control Explorer has specific knowledge about TFS.

So when you look in the Properties Window for the path of the file you are interested in, then you can use the Source Control Explorer to locate the file, and find out who has checked out that file.

There are other tools that can even give your more information than the Source Control Explorer:

  • the TF command-line application (on your PATH when you start the Visual Studio Command Prompt shortcut) to obtain extra information.
  • the Team Foundation Sidekicks (free; version 3.0 is for Team Foundation Server 2010; 2.4 is for Team Foundation Server 2008/2005) even produce most of that info from a GUI.
These two Stack Overflow questions were relevant in answering the above:

Posted in .NET, Development, Software Development, Source Code Management, TFS (Team Foundation System), Visual Studio 2005, Visual Studio 2008, Visual Studio 2010, Visual Studio and tools | Leave a Comment »

Entity Framework: finding out what SQL is executed behind the scene

Posted by jpluimers on 2011/05/25

I love the Entity Framework, but as with every layer of abstraction, sometimes you need to get underneath in order to solve problems.

For EF questions, I usually browse the presentationsblogarticles or Entity Framework book from Julie Lerman.
I met her first at an SDC conference years ago: she has a great way of explaining new concepts in an easy to grasp way, not being afraid to do a deep dive into technology when needed.

Her article MSDN Magazine: Data Points – Profiling Database Activity in the Entity Framework is a great way to start digging for the actual SQL being executed by EF on your behalf.

It has a balanced list of ways to get that SQL, and describes the pros and cons for each means.

The comments point you to some more ways.

Recommended reading!

–jeroen

Posted in .NET, Development, EF Entity Framework, Software Development | Leave a Comment »

mijnalbum.nl URLs and downloading pictures

Posted by jpluimers on 2011/05/24

MijnAlbum.nl is a popular site for storing and printing photos.

The UX of the site is far below what I’d like so I searched around for some scripts and wrote a bit of code for my own to make it easier.

First a few URL tricks for mijnalbum.nl (with the free demo album with Album ID TYEGMIMD):

  1. Album URLs follow this pattern:
    http://www.mijnalbum.nl/Album=TYEGMIMD
    where the letters after Album= contain the Album ID.
  2. When you click on a photo a new window opens with a URL like
    http://www.mijnalbum.nl/GroteFoto-3ANGJPWW.jpg
    where the letters after GroteFoto- contain the Photo ID and the .jpg extension.
    You don’t need to be logged in to download these photos.
  3. The album page includes a frame with thumbnails that has a URL like
    http://www.mijnalbum.nl/index.php?m=albumview&a=2&key=TYEGMIMD&selectedfoto=3ANGJPWW
    but a bit of experimentation reveals it can be condensed into
    http://www.mijnalbum.nl/?m=albumview&a=2&key=TYEGMIMD
    where the letters after key= contain the Album ID.
  4. The thumbnail frame contains photo’s that link to URLs like
    http://www.mijnalbum.nl/index.php?m=albumview&a=1&key=3ANGJPWW&album=TYEGMIMD
    that can be condensed into
    http://www.mijnalbum.nl/?m=albumview&a=1&key=3ANGJPWW&album=TYEGMIMD
    where you both need the Photo ID as key value, and Album ID as album value.
    The thumbnails are tiny, so not very convenient to browse.
  5. Download URLs look like this
    http://www.mijnalbum.nl/index.php?m=download&a=10&key=TYEGMIMD
    which can be condensed into
    http://www.mijnalbum.nl/?m=download&a=10&key=TYEGMIMD
    but you need to be logged in to download other albums than the demo album.

The thumbnails frame contains two lists of the photos in the album. Given the demo album, it first contains a this section inside a bunch of JavaScript code:

thumbs.push(new Array("http://www.mijnalbum.nl/MiniFoto-3ANGJPWW.jpg"));
thumbs.push(new Array("http://www.mijnalbum.nl/MiniFoto-6OKRE67M.jpg"));
thumbs.push(new Array("http://www.mijnalbum.nl/MiniFoto-4OSAXTJM.jpg"));
thumbs.push(new Array("http://www.mijnalbum.nl/MiniFoto-7MFJVO4F.jpg"));
thumbs.push(new Array("http://www.mijnalbum.nl/MiniFoto-YQ4BZ4AD.jpg"));
thumbs.push(new Array("http://www.mijnalbum.nl/MiniFoto-3LKQD6AG.jpg"));
thumbs.push(new Array("http://www.mijnalbum.nl/MiniFoto-O8RUL378.jpg"));
thumbs.push(new Array("http://www.mijnalbum.nl/MiniFoto-7TTFUUCG.jpg"));
thumbs.push(new Array("http://www.mijnalbum.nl/MiniFoto-L6SLLZHO.jpg"));
thumbs.push(new Array("http://www.mijnalbum.nl/MiniFoto-YLSWWFJI.jpg"));
thumbs.push(new Array("http://www.mijnalbum.nl/MiniFoto-CFWOY8KK.jpg"));

and further in the page source a HTML table with HTML fragements like these:

        <a onclick="resetScrollNextImg();" onfocus="this.blur();" href="index.php?m=albumview&a=1&key=3ANGJPWW&album=TYEGMIMD" target="fotoframe">
 <img id="thumb-3ANGJPWW" style="margin-bottom: -3px;" title="Eendjes in de wei" src="http://www.mijnalbum.nl/MiniFoto-3ANGJPWW.jpg" alt="Eendjes in de wei" width="90" height="90" border="0" />
 </a>

The HTML fragment has more context (Picture ID in both the a and img tags, Picture description in the alt attribute of the img tag).

You need to parse either of the two tables, depending on what information you are interested in.

I was interested in the thumbnail URL, and the Photo IDs and GroteFoto download URLs because it is way easier to select photos that are bigger. Something like this list:

Thumbnail URL for Album TYEGMIMD
http://www.mijnalbum.nl/index.php?m=albumview&a=2&key=TYEGMIMD
Photo URLs for Album TYEGMIMD











Since the thumbnail URL page is not xhtml, you have two options:

  • Force the page to become XHTML by some library
  • Use Regular Expressions

Though I am not a fan of using Regular Expressions for parsing general HTML, the thumbnail frame is generated in a very consistent way, so in this case I don’t mind using RegEx.

A complete console app is part of the bo.codeplex.com library.
This is the C# code I wrote as a base:

using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;

namespace MijnAlbum.NL.Download.ConsoleApplication
{
    public class MijnAlbumNl
    {
        protected const string ThumbnailPrefix = "http://www.mijnalbum.nl/index.php?m=albumview&a=2&key=";
        protected const string BigJpegUrlMask = "http://www.mijnalbum.nl/GroteFoto-{0}.jpg";

        private static string DownloadString(string url)
        {
            var html = string.Empty;
            using (var webClient = new System.Net.WebClient())
            {
                html = webClient.DownloadString(url);
            }
            return html;
        }

        protected static string DownloadThumbnailsHtml(string AlbumID)
        {
            string url = GetThumbnailsUrl(AlbumID);
            string html = DownloadString(url);
            return html;
        }

        protected static string GetThumbnailsUrl(string AlbumID)
        {
            string url = ThumbnailPrefix + AlbumID;
            return url;
        }

        protected static List getPhotoIds(bool dumpGroups, string html)
        {
            List photoIds = new List();
            /* find strings like these:
            thumbs.push(new Array("http://www.mijnalbum.nl/MiniFoto-3ANGJPWW.jpg"));
            thumbs.push(new Array("http://www.mijnalbum.nl/MiniFoto-6OKRE67M.jpg"));
                         * RegEx string:
            thumbs\.push\(new\ Array\("http://www.mijnalbum.nl/MiniFoto-(?.*?)\.jpg"\)\);
                         */
            // With @, you only have to escape the double quotes with another double quote: http://weblogs.asp.net/lorenh/archive/2004/09/30/236134.aspx
            const string RegExPattern = @"thumbs\.push\(new\ Array\(""http://www.mijnalbum.nl/MiniFoto-(?.*?)\.jpg\""\)\);";
            const string PhotoIdRegExCaptureGroupName = "PhotoId";
            //const string RegExReplacement = @"${PhotoId}";
            MatchCollection matchCollection = Regex.Matches(html, RegExPattern);
            // Matches uses lazy evaluation, so each match will be evaluated when it is accessed in the loop
            foreach (Match match in matchCollection)
            {
                Group positionIdGroup = match.Groups[PhotoIdRegExCaptureGroupName];
                if (dumpGroups)
                    Console.WriteLine(positionIdGroup.Value);
                photoIds.Add(positionIdGroup.Value);
            }
            return photoIds;
        }

        protected static string GetBigJpegUrl(string photoId)
        {
            string bigJpegUrl = string.Format(BigJpegUrlMask, photoId);
            return bigJpegUrl;
        }

    }

}

Note that others wrote some scripts too, so for instance Kees Hink  wrote on Foto’s downloaden van mijnalbum.nl and there is the MijnAlbumDownloader app.

Note 2: The free RegEx Expresso tool is very nice for building and testing Regular Expressions.

–jeroen

Posted in .NET, C#, Development, Software Development | 3 Comments »

Better solution for C# Warning CS0067 than “#pragma warning disable 0067”: The event ‘event’ is never used – Trevor’s Dev Blog – Site Home – MSDN Blogs

Posted by jpluimers on 2011/05/19

When you get a C# Warning CS0067, the MSDN documentation tell you to insert a “#pragma warning disable 0067”, but Trevor Robinson has a better solution at C# Warning CS0067: The event ‘event’ is never used – Trevor’s Dev Blog – Site Home – MSDN Blogs:

Since the event is never used, make the event explicit, or even throw an exception in the add clause of the event.

–jeroen

Posted in .NET, C#, C# 2.0, C# 3.0, C# 4.0, Development, Software Development | Leave a Comment »

Simple example to show DateTime.Now in ISO 8601 format on ideone.com | Online C# Compiler & Debugging Tool

Posted by jpluimers on 2011/05/17

I’m a fan of ISO 8601, as it is a universal way of expressing dates and times (no more MDY confusion ).

I wrote about using ISO 8601 in batch-files and with Google Calendar before.

Now it is time to give you a simple C# example.

When you realize that XML uses ISO 8601 for their date and time formats, the .NET conversion is very easy:

using System;
using System.Xml;

public class Test
{
    public static void Main()
    {
        string Iso8601DateTime =
            XmlConvert.ToString(DateTime.Now, XmlDateTimeSerializationMode.Local);
        Console.WriteLine(Iso8601DateTime);
    }
}

I wrote about ideone.com before: it is an excellent place to run sample C# code (and other languages).

When running this on ideone.com, you can see their local server time in ISO 8601 format.
Cute :-)

BTW: There are more ways to run your C# code online.

–jeroen

via: Simple example to show DateTime.Now in ISO 8601 format on Ideone.com | Online C# Compiler & Debugging Tool.

Posted in .NET, C#, Development, ISO 8601, Power User, Software Development | 1 Comment »

How to Get Paths and URL fragments from the HttpRequest object

Posted by jpluimers on 2011/05/12

There are many ASP.NET HttpRequest properties.

Sadly, the MSDN documentation does not have many examples telling you which property maps to which portion of the URL.

So it usually is a big fight extracting the sub portions you need.

Luckily, Steve Lautenschlager has the How Do I Get Paths and URL fragments from the HttpRequest object? article online.
The article has a table with the properties and portions of the URL that end up in those properties.

Really neat, as it saves a lot of time.

–jeroen

Posted in .NET, ASP.NET, Development, Software Development | Leave a Comment »