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App.Config cannot access appSettings key/value pairs. The collection is always null

I have an app.config that I am trying to get values out of and I am in a solution that is an executable. I have compared the output config.exe and everything is visible. When I try to set these values, they simply do not show up in the collection.
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
</startup>
<appSettings>
<add key="a" value="b"/>
</appSettings>
</configuration>
I have tried everything that I can think of and have never had this problem before. This is part of a larger solution where I cannot show the real values, but I have tested them in a console project that I created and they show up just fine. I am not sure why they wouldn't show up in this particular solution. Could any third party tools effect this?
I am trying to access them like this:
using System.Configuration;
private readonly string stringToSet;
public TheConstructor()
{
stringToSet = ConfigurationManager.AppSettings[key];
}
UPDATE I just figured out that for some reason, a class library is somehow hijacking my app.config. The solution that I am referencing the app.config thinks that I need my keys from .dll.config. How is this possible? The project that I am using the config is referencing it in the same project, not from a class library. How can this happen?

Add More than One Custom Sections to App Config C#?

I would like to make an app.config that looks like
<configuration>
<SQLconneciton>
<add key=name/>
<add key= otherStuff/>
</SQLconnection>
<PacConnection>
<add key=name/>
<add key= otherStuff/>
</PacConnection>
</configuration>
I've read many examples where people make ONE custom section and add stuff, I need to allow the user to add multiple sections, read, delete. I don't really need fancy elements, just simple add and key values. Is section groups worth using or is there something easy I'm missing?

Sure - there's really nothing stopping you from creating as many custom config sections as you liked!
Try something like this:
<?xml version="1.0"?>
<configuration>
<!-- define the config sections (and possibly section groups) you want in your config file -->
<configSections>
<section name="SqlConnection" type="System.Configuration.NameValueSectionHandler"/>
<section name="PacConnection" type="System.Configuration.NameValueSectionHandler"/>
</configSections>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
</startup>
<!-- "implement" those config sections as defined above -->
<SqlConnection>
<add key="abc" value="123" />
</SqlConnection>
<PacConnection>
<add key="abc" value="234" />
</PacConnection>
</configuration>
The System.Configuration.NameValueSectionHandler is the default type to use for a config section that contains <add key="...." value="....." /> entries (like <appSettings>).
To get the values, just use something like this:
NameValueCollection sqlConnConfig = ConfigurationManager.GetSection("SqlConnection") as NameValueCollection;
string valueForAbc = sqlConnConfig["abc"];
And you can absolutely mix and match existing section handler types as defined by .NET as well as your own custom config sections, if you've defined some of those yourself - just use whatever you need!

Edit App.Config name-value pairs from a separate tool

I am trying to create a simple tool for a service person to update a few entries in the App.Config of a different program. The App.Config file contains custom parameters used upon initialization of our program.
Since the App.Config contains many sensitive items a tool is needed to ensure only certain parameters are changed. Thus, the reason not to allow them to edit the App.Config directly.
My questions:
How can I access the name-value pairs from the config sections of an App.config from a separate program?
Which is better suited for the UI: Winforms or WPF? Are their controls that make it easy to add more entries in the future?
The tool should allow the user to set either a String, int, double or Boolean.
Here is the structure of the App.Config:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
<sectionGroup name="Settings">
<section name="Section1" type="System.Configuration.NameValueSectionHandler"/>
<section name="Section2" type="System.Configuration.NameValueSectionHandler"/>
<section name="Section3" type="System.Configuration.NameValueSectionHandler"/>
<section name="Section4" type="System.Configuration.NameValueSectionHandler"/>
</sectionGroup>
</configSections>
<Settings>
<Section1>
<add key="NAME_STRING" value="Some String"/>
</Section1>
<Section2>
<add key="NAME_INTEGER" value="10"/>
</Section2>
<Section3>
<add key="NAME_DOUBLE" value="10.5"/>
</Section3>
<Section4>
<add key="NAME_BOOLEAN" value="true"/>
</Section4>
</Settings>
... Omitted ...
</configuration>
In the program which uses the App.Config itself, I can easily change the values like so:
NameValueCollection nvc = (NameValueCollection)ConfigurationManager.GetSection("Settings/Section1");
Is there a similar way to do this from a separate program after loading the App.Config?

An answer to Question 1: An app.config file is an XML file. It might be easiest to load it as an XML document and modify that programmatically, followed by a save, than to use System.Configuration classes.
ETA: I believe it can be done with ConfigurationManager. Look at the OpenMappedExeConfiguration method. There's a good example there.

You could treat the app.config file as a normal XML file. Use either XDocument or XmlDocument to load the file.
Then use XPath or Linq to XML to find the name-value pairs.
As for Windows.Forms vs. WPF, its a design decision. Both have good and bad points.
[Update]
If you still want to use System.Configuration, you can use the ConfigurationManager.OpenExeConfiguration to get access to the other program's app.config file. This returns a Configuration object, which has a GetSection method.

c# Application Configuration File: AppSettings Reads Empty?

This is my first time using an XML config file. In the solution explorer I right click, add, new item, application config. file.
I then edited the file to read...
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<appSettings>
<add key="Key1" value="1000" />
</appSettings>
</configuration>
...and tried to access it with...
Int32.Parse(ConfigurationManager.AppSettings.Get("Key1"));
...but it says that the parameter is null. I looked at just ConfigurationManager.AppSettings and it's AllKeys property has dimension 0.
What am I doing wrong?
Thanks!

Right-click on your project, choose Properties>Settings tab and edit your settings there because the config file is not the only place these values are stored at.
In your code use Settings.Default.MySetting to access the settings.
You'll need to add using MyProjectName.Properties; to your using statements in order to access the settings this way or you'll have to fully qualify it as MyProjectName.Properties.Settings.Default.MySetting...

I know this is super old but I just encountered this opening an old project. A reference to System.Configuration was missing.

To ensure get information from App.config using ConfigurationManager.AppSettings["<Key name>"]; be sure to set your values inside <appSettings> section.
Example:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.7.2" />
</startup>
<appSettings>
<add key ="IntervalSeconds" value ="60000"/>
<add key ="OutputPathLog" value ="\\myserver\hackingtrack\Projects\Log\"/>
<!--Jorgesys si Elenasys sunt puisori-->
<add key="InputFeeds1" value="https://cld.blahbla.com//portadaKick.json" />
<add key="InputFeeds2" value="https://cld.blahbla.com//portadaKick.json" />
<add key="InputFeeds3" value="https://cld.blahbla.com//portadaKick.json" />
</appSettings>
</configuration>
Retrieving values:
string intervalSeconds = ConfigurationManager.AppSettings["IntervalSeconds"];
string inputFeeds1 = ConfigurationManager.AppSettings["InputFeeds1"]; ;
string inputFeeds2 = ConfigurationManager.AppSettings["InputFeeds2"];
string inputFeeds3 = ConfigurationManager.AppSettings["InputFeeds3"];

How to use a App.config file in WPF applications?

I created an App.config file in my WPF application:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<appsettings>
<add key="xmlDataDirectory" value="c:\testdata"/>
</appsettings>
</configuration>
Then I try to read the value out with this:
string xmlDataDirectory = ConfigurationSettings.AppSettings.Get("xmlDataDirectory");
But it says this is obsolete and that I should use ConfigurationManager which I can't find, even searching in the class view.
Does anyone know how to use config files like this in WPF?

You have to reference the System.Configuration assembly which is in GAC.
Use of ConfigurationManager is not WPF-specific: it is the privileged way to access configuration information for any type of application.
Please see Microsoft Docs - ConfigurationManager Class for further info.

In my case, I followed the steps below.
App.config
<configuration>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
</startup>
<appSettings>
<add key="POCPublishSubscribeQueueName" value="FormatName:Direct=OS:localhost\Private$\POCPublishSubscribe"/>
</appSettings>
</configuration>
Added System.Configuartion to my project.
Added using System.Configuration statement in file at top.
Then used this statement:
string queuePath = ConfigurationManager.AppSettings["POCPublishSubscribeQueueName"].ToString();

In your app.config, change your appsetting to:
<applicationSettings>
<WpfApplication1.Properties.Settings>
<setting name="appsetting" serializeAs="String">
<value>c:\testdata.xml</value>
</setting>
</WpfApplication1.Properties.Settings>
</applicationSettings>
Then, in the code-behind:
string xmlDataDirectory = WpfApplication1.Properties.Settings.Default.appsetting.ToString()

You have to reference System.Configuration via explorer (not only append using System.Configuration). Then you can write:
string xmlDataDirectory =
System.Configuration.ConfigurationManager.AppSettings.Get("xmlDataDirectory");
Tested with VS2010 (thanks to www.developpez.net).
Hope this helps.

You have to add the reference to System.configuration in your solution. Also, include using System.Configuration;. Once you do that, you'll have access to all the configuration settings.

This also works
WpfApplication1.Properties.Settings.Default["appsetting"].ToString()

You can change configuration file schema back to DotNetConfig.xsd via properties of the app.config file. To find destination of needed schema, you can search it by name or create a WinForms application, add to project the configuration file and in it's properties, you'll find full path to file.

There is a good article about Application settings on Microsoft.
According to that you need to:
manually create App.config file (from Project Context menu -> Add -> New Item... -> Application Configuration File.)
add required sections there (I'm using only application scope settings):
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<configSections>
<sectionGroup name="applicationSettings"
type="System.Configuration.ApplicationSettingsGroup, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
<section name="DevelopmentEnvironmentManager.WPF.Properties.Settings"
type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
</sectionGroup>
</configSections>
<applicationSettings>
<DevelopmentEnvironmentManager.WPF.Properties.Settings>
<setting name="SqliteDbFilePath" serializeAs="String">
<value>Database.db</value>
</setting>
<setting name="BackgroundColor" serializeAs="String">
<value>White</value>
</setting>
<setting name="TextColor" serializeAs="String">
<value>Black</value>
</setting>
</DevelopmentEnvironmentManager.WPF.Properties.Settings>
</applicationSettings>
</configuration>
NOTE: Replace 'DevelopmentEnvironmentManager.WPF' with the name of your application.
Additionally, you can go to Properies of the project and add Settings.Designer:
this will add convenient designer to your project, so you don't have to edit XML manually:
To access settings from the code - simply save and close all config editors, build app and access static Propeties (again, do not forget to change app name in the namespace):
string databasePath = DevelopmentEnvironmentManager.WPF.Properties.Settings.Default.SqliteDbFilePath;

I have a Class Library WPF Project, and I Use:
'Read Settings
Dim value as string = My.Settings.my_key
value = "new value"
'Write Settings
My.Settings.my_key = value
My.Settings.Save()