app.config read value of key connection string from other node

Question

On stackoverflow are a couple of questions regarding how the get app.config values from code or using windows path variables.

But I would like to know if i can use an already defined key inside the app.config xml file?
The purpose is to avoid entereing the connection string many times.

Below you can see my connection string 'con_str':

<appSettings>
  <add key="con_str" value="myDatabaseConnectionString"/>
</appSettings>
....
<log4net>
    <appender name="AdoNetExceptionAppender" 
         type="log4net.Appender.AdoNetAppender">
      <bufferSize value="1" />
      <threshold value="FATAL"/>
      <connectionType ... />
      <connectionString 
                 value= .... <--- How to use value from 'con_str' above?
       />
      <commandText ... />
      <parameter>
        <parameterName value="@log_date" />
        <dbType value="DateTime" />
        <layout type="log4net.Layout.RawTimeStampLayout" />
      </parameter>
    </appender>
</log4net>

Is there a way to read the value of the key con_str from the appSettingsnode within app.config?

Update 1 after comment from user chadiusvt

I changed my app.config like this:

<appSettings>
    <add key="con_strOrig" value="foo" />   
</appSettings>
<connectionStrings>
    <add name="connStr" connectionString="foo" />   
</connectionStrings>
    ...
<log4net>
  <appender name="AdoNetExceptionAppender" 
            type="log4net.Appender.AdoNetAppender">
  <bufferSize value="1" />
  <threshold value="FATAL"/>
  <connectionType ... />
  <connectionString value="connStr"  />
  ...

As you can see with the last update it is possible to reference the connectionStrings. But since in my code i always use appSettings i would have to change my code in many places. Is there a way to let the <appSettings> point to the connStr key from the node <connectionsStrings>?

Update 2 to adress the answer

I believe you misunderstood. I am looking for a way to reference another var inside the xml-file.

Maybe [this article](http://stackoverflow.com/questions/2441359/can-you-pull-the-connectionstring-for-a-log4net-adonetappender-from-elsewhere-in) would be of help? It doesn't specify the connectionstring by name, but if you only have one, this might be sufficient. — Soturi, Sep 09 '13 at 13:55

score 3 · Answer 1 · answered Sep 09 '13 at 14:14

3

Simply use this line :

System.Configuration.ConfigurationManager.AppSettings["con_str"]

answered Sep 09 '13 at 14:14

Franck

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I believe you misunderstood. I would like to reference the value from the connectionstring from inside the app.config xml-file. The following did not work: `` – surfmuggle Sep 09 '13 at 18:53
you can use the line above to READ the settings then by code set the log 4 net equals to that one. so you only have 1 to manage. – Franck Sep 09 '13 at 20:02
yes like in program.cs when you start the application you can override these settings. just read the "con_str" and set the log4net one. – Franck Sep 10 '13 at 17:18

score 1 · Answer 2 · edited Nov 04 '14 at 14:09

1

As of my knowledge it's not possible to assign the section name with values.

I've some alternative solution to accomplish your task.

Assign name in to value dynamically in Program.CS

string connectionString = ConfigurationManager
  .ConnectionStrings["connStr"].ConnectionString;
ConfigurationManager.AppSettings
  .Set("con_strOrig", connectionString);

edited Nov 04 '14 at 14:09

Konrad Viltersten

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answered Sep 10 '13 at 13:00

Bala

618
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app.config read value of key connection string from other node

Update 1 after comment from user chadiusvt

Update 2 to adress the answer

2 Answers2