The ASP.NET GridView control can be a really useful control for displaying and editing tabular data, but if you try to make it work with MySQL or a cross-tab query you’re likely to run into problems.
I wanted to create a grid showing the data from a cross-tab but also allow users to edit the data. If you’ve never used one before, a cross tabulation is a query which maps repeating rows to columns instead. This means that a column in a displayed result might not actually exist as a column in a database table. If you just need to display the data and aren’t bothered about editing it, the GridView works out of the box and will automatically generate the columns for you – but what if you need to display some columns but not others?
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I was working on ResourceBlender last week trying to find a way to get the data from multiple rows in SQL. I thought I’d have to loop through programatically and abuse Dictionaries and HashTables until I found out about a lesser known and at first confusing feature of SQL known as cross tabulation.
The data I needed contained translations. I have a table for elements and a table for translations, and each translation can be used by multiple elements.
mysql> SELECT elementname, LANGUAGE, translation, elements.translationid
FROM elements
INNER JOIN translations ON translations.translationid = elements.translationid
WHERE elements.translationid
BETWEEN 24 AND 25;
+-------------+----------+-------------------+---------------+
| elementname | LANGUAGE | translation | translationid |
+-------------+----------+-------------------+---------------+
| PrevWeek | de-DE | Vorherige Woche | 24 |
| PrevWeek | en-GB | Previous Week | 24 |
| PrevWeek | es-ES | Semana anterior | 24 |
| PrevWeek | nl-NL | Vorige week | 24 |
| PrevWeek | ro-RO | Saptamana trecuta | 24 |
| PrevMonth | cs-CZ | Předchozí rok | 25 |
| PrevMonth | de-DE | Vorheriger Monat | 25 |
| PrevMonth | el-GR | Προηγ. Ετος| 25 |
| PrevMonth | en-GB | Previous Month | 25 |
| PrevMonth | es-ES | Año anterior | 25 |
| PrevMonth | fr-FR | Préc. An | 25 |
| PrevMonth | it-IT | Anno prec. | 25 |
| PrevMonth | nl-NL | Vorig jaar | 25 |
| PrevMonth | pl-PL | Poprzedni rok | 25 |
| PrevMonth | pt-PT | Ano anterior | 25 |
| PrevMonth | ro-RO | Luna trecuta | 25 |
| PrevMonth | ru-RU | Предыдущий год| 25 |
| PrevMonth | sl-SI | Prejšnje leto | 25 |
| PrevMonth | sv-SE | Föreg. År | 25 |
| PrevMonth | tr-TR | րnceki Yýl | 25 |
| PrevMonth | zh-Hans | 上一年 | 25 |
+-------------+----------+-------------------+---------------+
21 rows IN SET
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If you have a page which uses a master page, then put controls inside a ContentPlaceHolder on the sub page, accessing the values of the controls can be difficult if you’re posting the form to another page. The problem is, the ContentPlaceHolder mangles the control names so instead of radApplication, you get ctl00$cntMain$radApplication, meaning you can’t read them from Request.Form.
Hardcoding the name of the placeholder would be a bad idea incase you ever change the name of it or change the master page. There are actually two ways you can get at the controls.
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After someone suggested a way to match URLs and protocols with wildcards in LockCrypt, I started work implementing a URL which accepted wildcard (*) characters. The result is a class which takes a URL string as a constructor and breaks it apart into it’s component parts. The class is based on a JavaScript regex from Steve Levithan.
The full specification for the URL it constructs is protocol://user:password@host:port/direc/tory/file?query#ref. Any parts left blank are assumed to be wildcards. Performance averages out to about 0.05ms per check, not bad for a beefy regex.
Just the constructor is listed here, the full source is available at http://leghumped.com/WildcardURL.java.
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I’ve spent the last half an hour tweaking this so it works. This batch file will loop through all files in the source directory with the specified extension and add each one to an individual .rar file with maximum compression.
As it is, it will add all files the the extension nds in the current directory to a new subdirectory called zipped.
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If you’ve ever needed a static method to load a resource, there’s a lot of conflicting information about how to get a resource contained in your JAR. I tried SomeProg.class.getClassLoader() and a few others but ended up with either a null value or an exception. Eventually on a whim I tried the following, which worked.
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I recently switched from WordPress to Movable Type for my software blogs. This site still runs WordPress because there are too many extensions which I need. My software blogs though, were just more or less the same site with different colours and about different products. I only use them for posting new release info and it was too much of an ordeal to update five WordPress blogs everytime an update was released.
One of the more annoying things about Movable type is the URL structure it uses by default. Everything is statically published by default, which works quite well and isn’t a problem in itself, but there’s something about seeing a .html or .php extension which makes a site look amateurish.
There’s an easy way to change Movable Type to use permalinks like http://leghumped.com/post-name instead of http://leghumped.com/2008/09/post-name.html
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DreamHost have been offering Subversion repositories with their hosting packages for the last couple of months, and if you're a developer, a central repository can be a useful thing to have.
Although DreamHost have a simple form for setting up a new repository and they make regular backups incase a hard drive fails, I still have a lingering fear of losing all of my source code. Luckily, DreamHost also offer SSH access and allow you to setup cron jobs to backup your data yourself. This guide provides instructions for creating a shell script to backup, compress, email and restore your SVN repository.
The tools you'll need to export a repository are svnadmin, tar, split, mutt – an email client, and optionally crontab.
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When Microsoft were deciding what to include in the .NET Compact Framework, they decided to restrict the OpenFileDialog and SaveFileDialog to the My Documents directory. There are plenty of reasons you’d need to choose a file outside of My Documents, so I coded a new file chooser from other components.
The dialog is just a form with a ComboBox which shows the current directory and all of it’s parents, a ListView which shows the files and directories in the current directory, and a text box to show the selected file.
Instantiate it with either the default constructor or a directory and file to show on startup.
FileInfo dbFile = new FileInfo("\\Storage Card\\Somefile.txt");
Lime49.OpenFileDialog dlg = new Lime49.OpenFileDialog(dbFile.DirectoryName, dbFile.Name);
dlg.Filter = "*.txt";
dlg.ShowDirectory(dbFile.DirectoryName);
dlg.ShowDialog();
MessageBox.Show(dlg.SelectedFile);The selected file is available through the SelectedFile property, and the filter doesn’t work the same way as standard FileDialogs, it uses a standard wildcard pattern to list files.
Download Lime49.OpenFileDialog
Also published on CodeProject
Last week I posted about drag and drop in C#. The post covered pre-built controls (TreeView and ListView). There are a few things the post didn't cover, such as user controls and anything which doesn't raise the ItemDrag event.
To be able to drag a user control, the control has to call the DoDragDrop method. The logical way to do this is by tracking the state of the left mouse button. If the left button is pressed and the mouse moves, start the drag/drop.
private bool isDragging = false;
...
private void userControl_MouseDown(object sender, MouseEventArgs e) {
this.isDragging = true;
};
private void userControl_MouseUp(object sender, MouseEventArgs e) {
this.isDragging = false;
};
private void userControl_MouseLeave(object sender, EventArgs e) {
isDragging = false;
};
private void userControl_MouseMove(object sender, MouseEventArgs e) {
if(isDragging) {
DoDragDrop(userControl, DragDropEffects.Move);
}
}; Read more »
