App.config add nested group to existing node

Question

I have to save 2 different groups of settings in my root settings group. It should looks like this:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>    
    <sectionGroup name="ROOT_GROUP">
       <sectionGroup name="GROUP_1">
         ........................
         some_settings
         ........................
       </sectionGroup>
       <sectionGroup name="GROUP_2">
         ........................
         some_other_settings
         ........................
       </sectionGroup>
     </sectionGroup>
  </configSections>
................................
other_system_tags
................................
</configuration>

The Nuance is that I have to save it one after another in different places in my code. (For example, GROUP_1 can be a connection strings and GROUP_2 is some environment settings and they both together are filling by users in different sections of my application)

I made this simple test class to get the expected result

[TestFixture]
public class Tttt
{
    private string ROOT_GROUP = "ROOT_GROUP";
    private string GROUP_1 = "GROUP_1";
    private string GROUP_2 = "GROUP_2";

    [Test]
    public void SaveSettingsGroups()
    {
        SaveGroup1();
        SaveGroup2();
        Assert.True(true);
    }

    private Configuration GetConfig()
    {
        var configFilePath = AppDomain.CurrentDomain.SetupInformation.ConfigurationFile;
        var map = new ExeConfigurationFileMap { ExeConfigFilename = configFilePath };
        var config = ConfigurationManager.OpenMappedExeConfiguration(map, ConfigurationUserLevel.None);
        return config;
    }

    private void SaveGroup1()
    {
        var config = GetConfig();

        var root = new UserSettingsGroup();

        config.SectionGroups.Add(ROOT_GROUP, root);

        config.Save(ConfigurationSaveMode.Modified);
        ConfigurationManager.RefreshSection(root.Name);

        var nested = new UserSettingsGroup();

        root.SectionGroups.Add(GROUP_1, nested);

        config.Save(ConfigurationSaveMode.Modified);
        ConfigurationManager.RefreshSection(nested.Name);             
    }

    private void SaveGroup2()
    {
        var config = GetConfig();

        var root = config.GetSectionGroup(ROOT_GROUP);

        var nested = new UserSettingsGroup();
        root.SectionGroups.Add(GROUP_2, nested);

        config.Save(ConfigurationSaveMode.Modified);
        ConfigurationManager.RefreshSection(nested.Name);
    }
}

BUT for some reason the result of this code is different

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>    
    <sectionGroup name="ROOT_GROUP">
      <sectionGroup name="GROUP_1">
        ........................
        some_settings
        ........................
      </sectionGroup>
    </sectionGroup>
    <sectionGroup name="ROOT_GROUP">
      <sectionGroup name="GROUP_2">
      ........................
      some_other_settings
      ........................
      </sectionGroup>
    </sectionGroup>
  </configSections>
................................
other_system_tags
................................
</configuration>

The ROOT_GROUP node is duplicated and of course visual studio throws me an exception that ROOT_GROUP is already exists. Obviously, my problem is hidden in method SaveGroup2() when I add new nested group to existed root group and then save it - but why?

UPD I've just added new method

    private void SaveGroup3()
    {
        var config = GetConfig();

        var root = config.GetSectionGroup(ROOT_GROUP);
        var nested1 = root.SectionGroups.Get(0);

        var nested2 = new UserSettingsGroup();
        var nested3 = new UserSettingsGroup();

        nested1.SectionGroups.Add("GROUP_2", nested2);
        root.SectionGroups.Add("GROUP_3", nested3);
        config.Save(ConfigurationSaveMode.Modified);
        ConfigurationManager.RefreshSection(nested2.Name);
        ConfigurationManager.RefreshSection(nested3.Name);
    }

And replace it in test

[Test]
public void SaveSettingsGroups()
{
    SaveGroup1();
    SaveGroup3();
    Assert.True(true);
}

And got this strange behaviour

  <sectionGroup name="ROOT_GROUP">
    <sectionGroup name="GROUP_1">
      <sectionGroup name="GROUP_2">
      </sectionGroup>
    </sectionGroup>
    <sectionGroup name="GROUP_3">
    </sectionGroup>
  </sectionGroup>

As you can see, the strangeness is in that the result is totally expected. ROOT_GROUP wasn't duplicate, as I needed it, but why it does in SaveGroup2()? Did I miss something in SaveGroup2()?

UPD2 - HACK

Just tried a simple idea - what if I would clear the root_group before adding a new nested element to it?

    private void SaveGroup2()
    {
        var config = GetConfig();

        var root = config.GetSectionGroup(ROOT_GROUP);

        var nested = new ConfigurationSectionGroup();

        //Copy exiting nested groups to array
        var gr = new ConfigurationSectionGroup[5];       
        root.SectionGroups.CopyTo(gr,0);
        gr[1] = nested;
        //<!----

        root.SectionGroups.Clear();

        config.Save(ConfigurationSaveMode.Modified);
        ConfigurationManager.RefreshSection(root.Name);

        root.SectionGroups.Add(gr[0].Name, gr[0]);
        root.SectionGroups.Add(GROUP_2, gr[1]);

        config.Save(ConfigurationSaveMode.Modified);
        ConfigurationManager.RefreshSection(root.Name);
    }

And how do you probably guess - it works!

<sectionGroup name="ROOT_GROUP">
  <sectionGroup name="GROUP_1" type="System.Configuration.UserSettingsGroup, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
  </sectionGroup>
  <sectionGroup name="GROUP_2" type="System.Configuration.ConfigurationSectionGroup, System.Configuration, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" >
  </sectionGroup>
</sectionGroup>

I think it looks like a bug or there are some hidden things that I missed. Can somebody explain me what did I do wrong?

Answer 1

It took me a while to figure-out what was going on and tl;dr it seems, to me, there is a problem with the framework code itself, particularly method WriteUnwrittenConfigDeclarationsRecursive(SectionUpdates declarationUpdates, XmlUtilWriter utilWriter, int linePosition, int indent, bool skipFirstIndent) inside class MgmtConfigurationRecord. I don't want to write a long story but if you wish you could debug .Net framework code and see for yourself.

You can fix your code in following ways:

1. Save all groups together

private void SaveGroups()
{
    var config = GetConfig();
    var root = new ConfigurationSectionGroup();
    config.SectionGroups.Add(ROOT_GROUP, root);
    config.Save(ConfigurationSaveMode.Modified);
    ConfigurationManager.RefreshSection(root.Name);

    var nested = new UserSettingsGroup();
    root.SectionGroups.Add(GROUP_1, nested);

    nested = new UserSettingsGroup(); 
    root.SectionGroups.Add(GROUP_2, nested);

    config.Save(ConfigurationSaveMode.Modified);
    ConfigurationManager.RefreshSection(root.Name);
}

2. Remove existing group items before adding a new one

private void SaveGroup2()
{
    var config = GetConfig();
    var root = config.SectionGroups[ROOT_GROUP];
    var existingGroups = new Dictionary<string, ConfigurationSectionGroup>();
    while (root.SectionGroups.Count > 0)
    {
        existingGroups.Add(root.SectionGroups.Keys[0], root.SectionGroups[0]);
        root.SectionGroups.RemoveAt(0);
    }

    config.Save(ConfigurationSaveMode.Modified);

    existingGroups.Add(GROUP_2, new UserSettingsGroup());
    foreach (var key in existingGroups.Keys)
    {
        existingGroups[key].ForceDeclaration(true);
        root.SectionGroups.Add(key, existingGroups[key]);
    }

    config.Save(ConfigurationSaveMode.Modified);
    ConfigurationManager.RefreshSection(root.Name);
}