[c#] Reading settings from app.config or web.config in .NET

I'm working on a C# class library that needs to be able to read settings from the web.config or app.config file (depending on whether the DLL is referenced from an ASP.NET web application or a Windows Forms application).

I've found that

ConfigurationSettings.AppSettings.Get("MySetting")

works, but that code has been marked as deprecated by Microsoft.

I've read that I should be using:

ConfigurationManager.AppSettings["MySetting"]

However, the System.Configuration.ConfigurationManager class doesn't seem to be available from a C# Class Library project.

What is the best way to do this?

I have been trying to find a fix for this same issue for a couple of days now. I was able to resolve this by adding a key within the appsettings tag in the web.config file. This should override the .dll file when using the helper.

<configuration>
    <appSettings>
        <add key="loginUrl" value="~/RedirectValue.cshtml" />
        <add key="autoFormsAuthentication" value="false"/>
    </appSettings>
</configuration>

Step 1: Right-click on references tab to add reference.

Step 2: Click on Assemblies tab

Step 3: Search for 'System.Configuration'

Step 4: Click OK.

Then it will work.

 string value = System.Configuration.ConfigurationManager.AppSettings["keyname"];

Right click on your class library, and choose the "Add References" option from the Menu.

And from the .NET tab, select System.Configuration. This would include the System.Configuration DLL file into your project.

Another possible solution:

var MyReader = new System.Configuration.AppSettingsReader();
string keyvalue = MyReader.GetValue("keyalue",typeof(string)).ToString();

If your needing/wanting to use the ConfigurationManager class...

You may need to load System.Configuration.ConfigurationManager by Microsoft via NuGet Package Manager

Tools->NuGet Package Manager->Manage NuGet Packages for Solution...

Microsoft Docs

One thing worth noting from the docs...

If your application needs read-only access to its own configuration, we recommend that you use the GetSection(String) method. This method provides access to the cached configuration values for the current application, which has better performance than the Configuration class.

I was able to get the below approach working for .NET Core projects:

Steps:

1. Create an appsettings.json (format given below) in your project.
2. Next create a configuration class. The format is provided below.

3. I have created a Login() method to show the usage of the Configuration Class.

   Create appsettings.json in your project with content:

   {
     "Environments": {
       "QA": {
         "Url": "somevalue",
    "Username": "someuser",
         "Password": "somepwd"
     },
     "BrowserConfig": {
       "Browser": "Chrome",
       "Headless": "true"
     },
     "EnvironmentSelected": {
       "Environment": "QA"
     }
   }
   
   public static class Configuration
   {
       private static IConfiguration _configuration;
   
       static Configuration()
       {
           var builder = new ConfigurationBuilder()
               .AddJsonFile($"appsettings.json");
   
           _configuration = builder.Build();
   
       }
       public static Browser GetBrowser()
       {
   
           if (_configuration.GetSection("BrowserConfig:Browser").Value == "Firefox")
           {
               return Browser.Firefox;
           }
           if (_configuration.GetSection("BrowserConfig:Browser").Value == "Edge")
           {
               return Browser.Edge;
           }
           if (_configuration.GetSection("BrowserConfig:Browser").Value == "IE")
           {
               return Browser.InternetExplorer;
           }
           return Browser.Chrome;
       }
   
       public static bool IsHeadless()
       {
           return _configuration.GetSection("BrowserConfig:Headless").Value == "true";
       }
   
       public static string GetEnvironment()
       {
           return _configuration.GetSection("EnvironmentSelected")["Environment"];
       }
       public static IConfigurationSection EnvironmentInfo()
       {
           var env = GetEnvironment();
           return _configuration.GetSection($@"Environments:{env}");
       }
   
   }
   
   
   public void Login()
   {
       var environment = Configuration.EnvironmentInfo();
       Email.SendKeys(environment["username"]);
       Password.SendKeys(environment["password"]);
       WaitForElementToBeClickableAndClick(_driver, SignIn);
   }
   

You can use the below line. In my case it was working: System.Configuration.ConfigurationSettings.AppSettings["yourKeyName"]

You must take care that the above line of code is also the old version and it's deprecated in new libraries.

For a sample app.config file like below:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="countoffiles" value="7" />
    <add key="logfilelocation" value="abc.txt" />
  </appSettings>
</configuration>

You read the above application settings using the code shown below:

using System.Configuration;

You may also need to also add a reference to System.Configuration in your project if there isn't one already. You can then access the values like so:

string configvalue1 = ConfigurationManager.AppSettings["countoffiles"];
string configvalue2 = ConfigurationManager.AppSettings["logfilelocation"];

The ConfigurationManager is not what you need to access your own settings.

To do this you should use

{YourAppName}.Properties.Settings.{settingName}

Also, you can use Formo:

Configuration:

<appSettings>
    <add key="RetryAttempts" value="5" />
    <add key="ApplicationBuildDate" value="11/4/1999 6:23 AM" />
</appSettings>

Code:

dynamic config = new Configuration();
var retryAttempts1 = config.RetryAttempts;                 // Returns 5 as a string
var retryAttempts2 = config.RetryAttempts(10);             // Returns 5 if found in config, else 10
var retryAttempts3 = config.RetryAttempts(userInput, 10);  // Returns 5 if it exists in config, else userInput if not null, else 10
var appBuildDate = config.ApplicationBuildDate<DateTime>();

web.config is used with web applications. web.config by default has several configurations required for the web application. You can have a web.config for each folder under your web application.

app.config is used for Windows applications. When you build the application in Visual Studio, it will be automatically renamed to <appname>.exe.config and this file has to be delivered along with your application.

You can use the same method to call the app settings values from both configuration files: System.Configuration.ConfigurationSettings.AppSettings["Key"]

Update for .NET Framework 4.5 and 4.6; the following will no longer work:

string keyvalue = System.Configuration.ConfigurationManager.AppSettings["keyname"];

Now access the Setting class via Properties:

string keyvalue = Properties.Settings.Default.keyname;

See Managing Application Settings for more information.

I had the same problem. Just read them this way: System.Configuration.ConfigurationSettings.AppSettings["MySetting"]

I always create an IConfig interface with typesafe properties declared for all configuration values. A Config implementation class then wraps the calls to System.Configuration. All your System.Configuration calls are now in one place, and it is so much easier and cleaner to maintain and track which fields are being used and declare their default values. I write a set of private helper methods to read and parse common data types.

Using an IoC framework you can access the IConfig fields anywhere your in application by simply passing the interface to a class constructor. You're also then able to create mock implementations of the IConfig interface in your unit tests so you can now test various configuration values and value combinations without needing to touch your App.config or Web.config file.

Try this:

string keyvalue = System.Configuration.ConfigurationManager.AppSettings["keyname"];

In the web.config file this should be the next structure:

<configuration>
<appSettings>
<add key="keyname" value="keyvalue" />
</appSettings>
</configuration>

Here's an example: App.config

<applicationSettings>
    <MyApp.My.MySettings>
        <setting name="Printer" serializeAs="String">
            <value>1234 </value>
        </setting>
    </MyApp.My.MySettings>
</applicationSettings>

Dim strPrinterName as string = My.settings.Printer

You might be adding the App.config file to a DLL file. App.Config works only for executable projects, since all the DLL files take the configuration from the configuration file for the EXE file being executed.

Let's say you have two projects in your solution:

• SomeDll
• SomeExe

Your problem might be related to the fact that you're including the app.config file to SomeDLL and not SomeExe. SomeDll is able to read the configuration from the SomeExe project.

I'm using this, and it works well for me:

textBox1.Text = ConfigurationManager.AppSettings["Name"];

Read From Config:

You'll need to add a reference to the configuration:

1. Open "Properties" on your project
2. Go to "Settings" Tab
3. Add "Name" and "Value"

4. Get Value with using following code:

   string value = Properties.Settings.Default.keyname;
   

Save to the configuration:

   Properties.Settings.Default.keyName = value;
   Properties.Settings.Default.Save();

As I found the best approach to access application settings variables in a systematic way by making a wrapper class over System.Configuration as below

public class BaseConfiguration
{
    protected static object GetAppSetting(Type expectedType, string key)
    {
        string value = ConfigurationManager.AppSettings.Get(key);
        try
        {
            if (expectedType == typeof(int))
                return int.Parse(value);
            if (expectedType == typeof(string))
                return value;

            throw new Exception("Type not supported.");
        }
        catch (Exception ex)
        {
            throw new Exception(string.Format("Config key:{0} was expected to be of type {1} but was not.",
                key, expectedType), ex);
        }
    }
}

Now we can access needed settings variables by hard coded names using another class as below:

public class ConfigurationSettings:BaseConfiguration
{
    #region App setting

    public static string ApplicationName
    {
        get { return (string)GetAppSetting(typeof(string), "ApplicationName"); }
    }

    public static string MailBccAddress
    {
        get { return (string)GetAppSetting(typeof(string), "MailBccAddress"); }
    }

    public static string DefaultConnection
    {
        get { return (string)GetAppSetting(typeof(string), "DefaultConnection"); }
    }

    #endregion App setting

    #region global setting


    #endregion global setting
}

Just for completeness, there's another option available for web projects only: System.Web.Configuration.WebConfigurationManager.AppSettings["MySetting"]

The benefit of this is that it doesn't require an extra reference to be added, so it may be preferable for some people.

I strongly recommend you to create a wrapper for this call. Something like a ConfigurationReaderService and use dependency injection to get this class. This way you will be able to isolate this configuration files for test purposes.

So use the ConfigurationManager.AppSettings["something"]; suggested and return this value. With this method you can create some kind of default return if there isn't any key available in the .config file.

You must add a reference to the System.Configuration assembly to the project.

Please check the .NET version you are working on. It should be higher than 4. And you have to add the System.Configuration system library to your application.