Question

Is it possible to add an custom configuration element at runtime.

Here is my app.config file

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="NodeList"
               type="Configuration.NodeListSection, NodeListConfiguration"
               requirePermission="false" />
  </configSections>
  <NodeList>
    <nodes>
      <add name="Dev1" isdefault="false" description ="Dev server" />
      <add name="QA1" isdefault="true" description="QA server"/>
      <add name="Prod1" isdefault="false" description="Production" />
    </nodes>
  </NodeList>
</configuration>

Can we add more nodes at runtime using C# code.

Answer 1

This doesn’t appear to be from a built-in configuration section. You will find that “NodesList” is an section/element that is custom written. To determine where in your codebase it is coming from look for “NodesList” at the top of your config file in the configSections element. That will point you at the class to look into.

After that, you need the class to support write operations properly.

To learn a lot more about customising configuration files there is a great series at CodeProject on the topic. In particular, the section on Saving Configuration Changes should be helpful to you.

Edit (after more info added to question):

Try something like (of course it all depends on what’s in NodeListSection codebase):

using Configuration;

var nodeListSection = ConfigurationManager.GetSection("NodeList") as Configuration.NodeListSection;
var newNode = new NodeElement() { Name = "xyz", IsDefault = false, Description = "New Guy" };
nodeListSection.Nodes.Add(newNode);

Configuration.Save(ConfigurationSaveMode.Modified);