Log4net writing custom object to sql database using custom appender? - sql-server-2012

Question

Using SQL Server 2012 here is my table:
CREATE TABLE [dbo].[Test]
(
[One] [VARCHAR](50) NOT NULL,
[Two] [VARCHAR](50) NOT NULL
) ON [PRIMARY]
Here is my appender:
<appender name="TestAppender" type="log4net.Appender.AdoNetAppender">
<bufferSize value="1" />
<connectionType value="System.Data.SqlClient.SqlConnection, System.Data, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
<connectionString value="data source=localhost;initial catalog=ApplicationLog;integrated security=false;persist security info=True;User ID=someUser;Password=somePassword" />
<commandText value="INSERT INTO [dbo].[Test] ([One],[Two]) VALUES (#one, #two)" />
<parameter>
<parameterName value="#one"/>
<dbType value="String"/>
<size value="50"/>
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%one"/>
</layout>
</parameter>
<parameter>
<parameterName value="#two"/>
<dbType value="String"/>
<size value="50"/>
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%two"/>
</layout>
</parameter>
</appender>
Here is how I get the instance of the logger in code and try to write to it:
private static readonly ILog TestLogger = LogManager.GetLogger("TestAppender");
TestLogger.Info(new Test {One = "someOne", Two = "someTwo"});
Here is my test class:
public class Test
{
public string One { get; set; }
public string Two { get; set; }
}
After stepping through this, I have a record in my table and the contents of the columns are this:
One: "one" Two: "12wo"
What the heck is "12wo"? I know I'm missing something here. I think my conversion patterns are wrong. I've tried this instead:
<conversionPattern value="%property{one}"/>
..but that doesn't work either. Do I have to write a custom pattern layout or something? Thanks.

Answer 1

This site pointed me in the right direction.
I had to create a custom LayoutPattern and PatternConverter in order to write my object to the log successfully. Turns out the weird "12wo" text I was getting in the database was because the conversion pattern uses printf c style syntax. Anyhow, here's some code.
public class TestLayoutPattern : PatternLayout
{
public TestLayoutPattern()
{
AddConverter(new ConverterInfo
{
Name = "test",
Type = typeof (TestConverter)
});
}
}
public class TestConverter : PatternConverter
{
protected override void Convert(System.IO.TextWriter writer, object state)
{
if (state == null)
{
writer.Write(SystemInfo.NullText);
return;
}
var loggingEvent = state as LoggingEvent;
if (loggingEvent == null)
throw new NullReferenceException("loggingEvent");
var test = loggingEvent.MessageObject as Test;
if (test == null)
{
writer.Write(SystemInfo.NullText);
}
else
{
switch (Option.ToLower())
{
case "one":
writer.Write(test.One);
break;
case "two":
writer.Write(test.Two);
break;
default:
writer.Write(SystemInfo.NullText);
break;
}
}
}
}
Here is how to get an instance of the logger by name:
private static readonly ILog TestLogger = LogManager.GetLogger("TestLogger");
Here is how to write a Test object to the log.
TestLogger.Info(new Test {One = "field one", Two = "field two"});
Here is how a parameter should be defined in the web.config.
<parameter>
<parameterName value="#one" />
<dbType value="String" />
<size value="50" />
<layout type="MyApp.TestLayoutPattern">
<conversionPattern value="%test{one}" />
</layout>
</parameter>
Another thing to note is the root and logger sections of the web.config. In the root section is where the default logger is defined with its level set. I can define my custom TestLogger in a logger section which will reference the appender as shown below. This allows me to access the TestLogger by name as shown above.
<root>
<level value="ALL"/>
<appender-ref ref="ADONetAppender"/>
</root>
<logger additivity="false" name="TestLogger">
<level value="ALL"/>
<appender-ref ref="TestAppender" />
</logger>
I also found if you wanted to just add a few properties to the default ADONetAppender (and add a few fields to the table), you could instead use the log4net.ThreadContext to set those properties like so:
log4net.ThreadContext.Properties["MyCustomPrperty"] = value;
Then in the web.config under the parameter section you can access that property like this:
<parameter>
<parameterName value="#myCustomProperty"/>
<dbType value="String"/>
<layout type="log4net.Layout.RawPropertyLayout">
<key value="MyCustomProperty" />
</layout>
</parameter>