How Can I Manage Configuration Settings for a DLL Used Across Multiple Applications?

Alternative to 'app.config' for DLLs

Question:

How can one store configuration settings specific to a DLL that may be used across multiple applications? Is there an equivalent to the 'app.config' file for DLLs?

Answer:

Creating a Dedicated Configuration File

While there is no direct equivalent to 'app.config' for DLLs, it is possible to create a separate configuration file for your DLL. This file should be named in the format 'DllName.dll.config.'

Obtaining Configuration Settings

To access configuration settings from this separate file, you can use the following code:

using System.Configuration;

namespace MyDLL
{
    public class ConfigurationHelper
    {
        public static string GetSetting(string key)
        {
            Configuration config = null;
            string dllPath = typeof(ConfigurationHelper).Assembly.Location;
            
            try
            {
                config = ConfigurationManager.OpenExeConfiguration(dllPath);
            }
            catch(Exception ex)
            {
                // Handle error, likely indicates missing configuration file.
            }
            
            if (config != null)
            {
                string value = GetAppSetting(config, "mySetting");
                return value;
            }

This code first attempts to open the configuration file associated with the DLL. If the file is found, it retrieves the setting with the specified key using the 'GetAppSetting' method:

private static string GetAppSetting(Configuration config, string key)
{
    KeyValueConfigurationElement element = config.AppSettings.Settings[key];
    if (element != null)
    {
        return element.Value;
    }

    return string.Empty;
}

Deployment and Output

To ensure that the configuration file is included when deploying the DLL, set the "Copy to Output Directory" property for the .config file to "Always Copy" in your Visual Studio project. This will ensure that the file is copied along with the DLL.

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