C# – Page 2 – Ash Tewari

Dial Gauge is a ProgressBar

I am not just being philosophical here. In WPF, ControlTemplates allow you to transform a control’s appearance. This is not the same as applying stylesheets. This is an entirely new level of customization. What you see in the screenshot below looks like a Dial but is actually a simple ProgressBar control wearing a “Dial” template. The Dial template was created using Microsoft Expression Blend .

Include the ControlTemplate as a Window.Resource and then assign it to ProgressBar element’s Template attribute :

Of course that is not all. The ControlTemplate must define some named elements of FrameworkElement type. Charles Petzold has explained it in detail : MSDN Magazine Article. So, I will not repeat it here.

The sample code can be downloaded here : DialTest.zip
License : Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.

PostSharp with SharpDevelop

SharpDevelop3.0 uses MSBuild. Including PostSharp in your build process is transparent if you are doing a global install using PostSharp installer. If you are doing a per-project installation using “Binary – No Installer” download, you will need to import the PostSharp targets into your .csproj file –


    True

C:\code\PostSharp-1.0.8.316-Binary\

For more details, read the install instructions included in the PostSharp download and under-the-hood-of-msbuild-integration.

To use local PostSharp binaries (relative to your project) , modify your .csproj file as follows –

  
    True
    $(MSBuildProjectDirectory)\PostSharp\

$(MSBuildProjectDirectory) is the directory containing your .csproj file.
\PostSharp\ is the directory containing local PostSharp binaries.

2. You will need to exclude the Aspect class itself from being woven.

If you are following the getting-started sample, see the following example:

[Serializable]
[Trace( null, AttributeExclude = true )]
public sealed class TraceAttribute : OnMethodBoundaryAspect
{

3. Compile your project.

Using Custom Converter in XAML

In my previous post : WPF-LINQ To SQL Sample, I had to resort to modifying .dbml file to get the images stored as varbinary into the WPF ListView control. I had to change the Type of image fields to System.Byte[], instead of using System.Data.Linq.Binary. A better way to do this is to use a custom converter. WPF allows you to specify custom converter as part of the Binding in .xaml, like this –

<Image Grid.Row="2"
Source="{Binding Path=ThumbNailPhoto ,
Converter={StaticResource imageConverter}}"></Image>

The custom converter is declared in the same .xaml file as a resource –

<Window.Resources>
<local:ImageDataConverter x:Key="imageConverter" />
</Window.Resources>

ImageDataConverter is implemented in .xaml.cs file –

public class ImageDataConverter : IValueConverter
{
   public object Convert(object value, Type targetType, object parameter,
   System.Globalization.CultureInfo culture)
   {
      byte[] image = ((System.Data.Linq.Binary)value).ToArray();
      return image;
   }

   public object ConvertBack(object value, Type targetType, object parameter,
   System.Globalization.CultureInfo culture)
   {
      throw new NotSupportedException();
   }
}

The updated sample code can be downloaded here : WPF-LINQ to SQL Sample
License : Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.

WPF – LINQ to SQL Sample

This exercise in binding a WPF ListView control with LINQ to SQL was a lot of fun ! The following image shows data from AdventureWorks sample database displayed in the ListView control. The end result is very admirable, even in this very basic demo. Feeling a complete sense of freedom is unavoidable when working with WPF.

This sample demonstrates :

LINQ to SQL mapping.
WPF ListView Control DataBinding.
Displaying images stored in database as varbinary in WPF control.

The sample code can be downloaded here : WPF-LINQ to SQL Sample
License : Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.

Customize log4net Output Path

The default log4net output path is relative to the startup directory of your executable. To customize the output path, you can override the base Appender’s File property in your own Appender class. The following example describes how to route the log files relative to the temp folder :

   public class MyOwnAppender : log4net.Appender.RollingFileAppender
   {
         public override string File
         {
             get
             {
                 return base.File;
             }

            set
            {
                if (Path.IsPathRooted(value))
                {
                    base.File = value;
                }
                else
                {
                    base.File = Path.Combine(Path.GetTempPath(), value);
                }
            }
        }
    }

Your log4net config file must be modified so that log4net can locate and use your custom Appender. If MyOwnAppender is in MyNamespace and you have implemented it in MyLoggerLib.dll :

Database Schema Version Control Tool

It is essential to treat database schema as source code and apply all the norms and best practices applicable to it. From what I hear and read, database schema version control is non-existent in too many projects.

Various techniques to accomplish version control of database schemas have been discussed and published. Martin Fowler and Pramod Sadagale has written a comprehensive article on Evolutionary Database Design. It is a must-read for everyone involved with database development.

K. Scott Allen writes in detail about an excellent system here – Versioning Databases – Change Scripts. This approach is sufficiently light-weight (for my taste) and provides complete control over the whole process.

I am providing a free tool here that you can use to implement this system. It will even create the SchemaVersionsLog table for your database, if it doesn’t exist. If you are using this tool with MSSQL Server, you can get started with very little effort. If you are using a different DBMS, you can still use this tool. It uses NHibernate to access the SchemaVersionsLog table. So, any DBMS supported by NHibernate is acceptable, as long as it comes with a command line tool to execute the sql scripts.

Download DbUpdater here.