NULL value in AppSettings - Accessing config file from Class Library

Question

I am trying to read value from appSettings but getting null value in return. Also getting null value in element variable present in my class file. Below is my class file content.

using System;
using System.Configuration;

namespace SampleDLL
{
    public class Class1
    {
        private static string GetAppSetting(Configuration config, string key)
        {
            var testValue = ConfigurationManager.AppSettings[key]; //Alternate option.
            var element = config.AppSettings.Settings[key];
            if (element == null) return string.Empty;
            var value = element.Value;
            return !string.IsNullOrEmpty(value) ? value : string.Empty;
        }

        public void GetDataAppConfig()
        {
            Configuration config = null;
            var exeConfigPath = GetType().Assembly.Location;
            try
            {
                config = ConfigurationManager.OpenExeConfiguration(exeConfigPath);
            }
            catch (Exception exception)
            {
                //handling exception here.
            }
            if (config != null)
            {
                var myValue = GetAppSetting(config, "myKey");
            }
        }
    }
}

My app.config file is as below

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="myKey" value="TestValue"/>
  </appSettings>
</configuration>

Reference to System.Configuration is present in my Class Library Project. I am calling GetDataAppConfig form from the one windows form present in another project of same solution.

Edited

I am using config file present in my Class Library Project.

My WinForm class is as below which I am using to call GetDataAppConfig present in classClass1 of class library project.

using System;
using System.Windows.Forms;
using SampleDLL;

namespace Test
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            var class1 = new Class1();
            class1.GetDataAppConfig();
        }
    }
}

Answer 1

The problem is that you're calling OpenExeConfiguration() with the wrong configuration file, by determining the configuration file using

var exeConfigPath = GetType().Assembly.Location;

You're actually using the path of the Class Library that defines your Class1 type when you actually want to load the configuration of the current client referencing Client1 (the WinForm app in your case).

Try this instead:

config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);

See MSDN

---

Update:

Since you want to embed the configuration file in your Class Library project, you'll have to follow the following steps:

• Change the file name from App.Config to something else (so that it won't collide with the client's configuration file).

• Change the Build Action of the file to Content

• Change Copy to output directory to Copy always

Then in your code:

try
{
    var configurationMap = new ExeConfigurationFileMap
    {
        // assuming name of your file is "ClassiLibrary1.config"
        ExeConfigFilename = Path.Combine(exeConfigPath, "ClassLibrary1.config")
    };

    config = ConfigurationManager.OpenMappedExeConfiguration(configurationMap, ConfigurationUserLevel.None);
}