你可以从web.config文件中的其他地方为log4net AdoNetAppender提取connectionString吗？

Question

I already have a db connection string in my web.config file. I scanned the log4net docs, but can't seem to find a way to use it within the log4net section of my web.config file. Is is possible to do something like this?

<connectionStrings>
    <add name="connStr" connectionString="Data Source=localhost; ..." />
</connectionStrings>

<log4net>
    <appender name="AdoNetAppender" type="log4net.Appender.AdoNetAppender">
    <connectionString connectionStringName="connStr"/>
      ...
</log4net>

Answer 1

It is possible to use a DB connection string specified in web.config without creating a new class, though you would need to use log4net build that hasn't been released yet. It can be downloaded from SVN repository http://svn.apache.org/viewvc/logging/log4net/trunk/

Your config will look as follows:

<connectionStrings>
    <add name="connStr" connectionString="Data Source=localhost; ..." />
</connectionStrings>

<log4net>
    <appender name="AdoNetAppender" type="log4net.Appender.AdoNetAppender">
    <connectionType value="System.Data.SqlClient.SqlConnection, System.Data, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
    <connectionStringName value="connStr" />
      ...
</log4net>

Please note that connectionType still needs to be specified.

Answer 2

Create a class that extends AdoNetAppender - say, WebAppAdoNetAppender . Implement the ConnectionString property in that class, and retrieve the connection string from your web.config file in that property setter.

<log4net>
    <appender name="AdoNetAppender" type="MyApp.WebAppAdoNetAppender">
    ...

...

public class WebAppAdoNetAppender : log4net.Appender.AdoNetAppender
{
    public new string ConnectionString
    {
        get { return base.ConnectionString; }
        set { base.ConnectionString = ...   }
    }
}

Answer 3

fyi this will be implemented in 1.2.11 according to this . however I have no idea when they are going to release it.

Answer 4

the answers above all do not work. i got another solution for this, i tried and it worked:

private static void ConfigureLog4Net()
{
    Hierarchy hierarchy = LogManager.GetRepository() as Hierarchy;
    if(hierarchy != null && hierarchy.Configured)
    {
        foreach(IAppender appender in hierarchy.GetAppenders())
        {
           if(appender is AdoNetAppender)
           {
               var adoNetAppender = (AdoNetAppender)appender;
               adoNetAppender.ConnectionString = ConfigurationManager.AppSettings["YOURCONNECTIONSTRINGKEY"].ToString();
               adoNetAppender.ActivateOptions(); //Refresh AdoNetAppenders Settings
           }
        }
    }
}

How i can use the connectionString of the current website for log4Net instead of configuring

Answer 5

As of 2017 (log4net 2.0.8.0 ), the following works:

public class MyAdoNetAppender : AdoNetAppender
{
    public MyAdoNetAppender()
    {
        ConnectionString = ...
    }
}


<appender name="AdoNetAppender" type="MyApp.MyAdoNetAppender">

(Very similar to @Michael Petrotta's answer)