Saturday, November 21, 2009

USB 2.0 vs. Firewire 400 vs. eSATA

To backup my data I bought the external harddisk Western Digital My Book Home Edition with a capacity of 1 Terabyte which provides the following interfaces:
  • 2 x Firewire 400
  • 1 x USB 2.0
  • 1 x eSATA
As I was curious to see how big is the difference between these interfaces I did some performance testing.
This are the results:

I did the perfomance testing under Windows Vista 64bit edition with the tool HDD Speed Test Tool by Marko Oette.
Regarding the eSATA interface I would like to say that the hot plug works (connect/disconnect while windows is running) and that while working with my computer I encountered sometimes some strange problems. The whole computer was blocked especially when I used applications that show an open file dialog or something similar. As soon as I unplugged the external HDD everything worked well. I would say that eSATA does not work 100%. This may be especially frustrating when making a backup of very large files and during the backup the HDD disappears (which happened to me). I don't exactly know if it is a driver, hardware or Windows Vista problem.

Search highlighting in WPF DataGrid

Unfortunately the DataGrid of the WPF-Toolkit does not provide a text highlighting feature out of the box; but sometimes it is very usefull for the users to be able to search for text or numbers in the datagrid to find the interesting information more quickly.
Tomer Shamam did a very good work which highlights a search key in different colors depending on which column they were found.

The only things which I don't like on his solution are:
  1. It works only if the datasource of the datagrid are objects
  2. That you have to define a style for every property you want to be highlighted in the datagrid which may be a big work if you have 15 properties for example
  3. When a row with a match is selected you do not see anymore which cell was highlighted
For my pupose I don't need the feature of the different coloring because I want only to highlight all cells in the datagrid where the search term is present in the same color. To resolve all of the above issues I changed the code of Shamam slightly.
You still need this two helper classes written by Shamam:
public class SearchTermConverter : IMultiValueConverter
public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
var stringValue = values[0] == null ? string.Empty : values[0].ToString();
var searchTerm = values[1] as string;

return !string.IsNullOrEmpty(searchTerm) &&
!string.IsNullOrEmpty(stringValue) &&

public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
throw new NotSupportedException();

public static class SearchOperations
public static string GetSearchTerm(DependencyObject obj)
return (string)obj.GetValue(SearchTermProperty);

public static void SetSearchTerm(DependencyObject obj, string value)
obj.SetValue(SearchTermProperty, value);

public static readonly DependencyProperty SearchTermProperty =
new FrameworkPropertyMetadata(string.Empty, FrameworkPropertyMetadataOptions.Inherits));

public static bool GetIsMatch(DependencyObject obj)
return (bool)obj.GetValue(IsMatchProperty);

public static void SetIsMatch(DependencyObject obj, bool value)
obj.SetValue(IsMatchProperty, value);

/* Using a DependencyProperty as the backing store for IsMatch. This enables animation, styling, binding, etc...*/
public static readonly DependencyProperty IsMatchProperty =
DependencyProperty.RegisterAttached("IsMatch", typeof(bool), typeof(SearchOperations), new UIPropertyMetadata(false));

As far as I understood this code defines a new dependancy property on the datagrid where the search term is stored and another dependancy property on each cell which stores wheter it is a match or not. Through the style which is defined in the Resource section of the page the "IsMatch" property is used to format the cell accordingly.
This is my modified XAML code to search the text of the datagrid instead of the property. Here you can also change the different colors if you like.
x:Key="SearchTermConverter" />

x:Key="{x:Static SystemColors.HighlightBrushKey}"
Color="Blue" />

Color="Yellow" />

Color="Red" />

TargetType="{x:Type toolkit:DataGridCell}">
Converter="{StaticResource SearchTermConverter}">
RelativeSource="{RelativeSource Self}"
Path="Content.Text" />
RelativeSource="{RelativeSource Self}"
Path="(local:SearchOperations.SearchTerm)" />
Value="{StaticResource HighlightColor}">
Value="True" />
Value="True" />
Value="{StaticResource SelectedHighlightedColor}"></Setter>

Then the style is assigned to the datagrid:
CellStyle="{StaticResource DefaultCell}"
Background="White" />

And finally the textbox connected to the "SearchTerm" property of the datagrid;
either via code in the TextChanged event of the TextBox:
SearchOperations.SetSearchTerm(this.dgvObjects, this.textBox1.Text);

or via XAML:
CellStyle="{StaticResource DefaultCell}"
local:SearchOperations.SearchTerm="{Binding ElementName=textBox1, Path=Text}" />

The result looks like this:

You can download the whole project from here.

Tuesday, November 17, 2009

SQL Server and legacy systems

Sometimes it happenes that we have to format the data which is stored in an SQL Server Database for an older system which requires the data to have a specific length. To achieve the length different datatypes are filled differently (at least in my case).
Lets take this example (we assume a length of 8):
- numbers have to be filled with zeros on the left (e.g. 66 -> 000066)
- strings have to be filled with spaces on the right (e.g. 'abc' -> 'abc ')

How can we achieve this?
Well the first problem is that we have to measure the length of the data and SQL Server provides two functions for that: 'LEN' and 'DATALENGTH'
This is not a problem you would say but it is because they behave differently. Look at the following examples:
Note the leading and trailing spaces of the strings!
"SELECT LEN(' abc ')" => 4
"SELECT DATALENGTH(' abc ')" => 5

"SELECT LEN(123)" => 3
"SELECT LEN(123.4567)" => 8

"SELECT DATALENGTH(999999999999)" => 9

Well this "strange" behaviour is because of what these functions do. Let's see the definition from MSDN on this:
LEN (Transact-SQL)Returns the number of characters of the specified string expression, trailing blanks.

Returns the number of bytes used to represent any expression.

So in principle I would say: if you want to know the number of characters of a value then you should use DATALENGTH for string values ( nchar, text, nvarchar,...) and LEN for numbers (int, float, decimal,...).

The next problem when filling values is the NULL value. According to the definition of the two functions is LEN(NULL) equal to NULL and DATALENGTH(NULL) also NULL. This may be a problem since I have to provide blanks or zeros if the value is NULL (e.g. ' ', 00000000).

The third problem is on how to fill the value with the requested fillers (zeros and blanks)? Well for this SQL Server provides a very nice function: REPLICATE
This function takes as input a character which should be replicated and a length. E.g.:
"SELECT REPLICATE('0', 10)" => 0000000000
"SELECT REPLICATE(' ', 10)" => ' '
This helps us to create what we want. So if we have the number '99' and we want it to fill on the left to a length of 8 we can do something like:
"SELECT REPLICATE('0', 8 - LEN(99)) + CAST(99 AS NCHAR)" => 00000099
"SELECT REPLICATE(' ', 8 - DATALENGTH(' abc ')) + ' abc '" => ' abc '
To fill on the right we have another possibility; it is casted to an NCHAR of the desired length; but this fills only with blanks:
"SELECT CAST(' abc ' AS NCHAR(8))" => ' abc    '
"SELECT CAST(99 AS NCHAR(8))" => '99 '
If you want to fill with something different then you have to use again the REPLICATE function as described above.

To handle the NULL value we use the case statement:
"SELECT CASE WHEN(null IS NOT NULL) THEN REPLICATE('0', 8 - LEN(null)) + CAST(null AS NCHAR) ELSE REPLICATE('0', 8) END" => '00000000'


Of course written like this it does not make much sense since we know in advance which part of the case statement is executed; but imagine you write in the place of the "null" or "99" the name of a column, then it makes perfectly sense. You can now easily write a case statement for string values.

Tuesday, November 3, 2009

Capturing Google Earth flight

Recently I created a photoshow from my photos of the summer and there I wanted also to add a Google Earth flight, so that everybody has an idea where this location is; and also because its simply cool :-)

On the internet they say that the pro edition has such a functionality but it costs 400$.
I tried then severeal screen capturing tools CamStudio or AutoScreenRecorder. They may be good to capture the screen to show other people how to perform some actions but for the Google Earth flight they are too slow. If they are capturing the flight isn't smoothly anymore.
Fortunately I found a very good tool which is also used to capture games. It is called Fraps and does a very very good job. I tried it with the OpenGL as well as with the DirectX mode of Google Earth and it works well with both of them. I think that after the test period it makes a watermark on the video but I can live with that.