WebAPI-DealerSelection/Source/DealerSelection.Common/Configuration/ConfigurationHelper.cs

using Microsoft.Extensions.Configuration;
using System.Configuration;
using System.Reflection;

namespace DealerSelection.Common.Configuration;

public static class ConfigurationHelper
{
    public static int SetEnvironmentVariables(string settingsFile)
    {
        IConfigurationRoot? config = LoadSettingsFile(settingsFile);
        int count = 0;

        if (config != null)
        {
            foreach (KeyValuePair<string, string?> pair in config.AsEnumerable())
            {
                if (pair.Value == null)
                    continue;

                Environment.SetEnvironmentVariable(pair.Key, pair.Value);
                count++;
            }
        }

        return count;
    }

    public static IConfigurationRoot? LoadSettingsFile(string settingsFile)
    {
        string basePath = FindBaseLocation(settingsFile);
        IConfigurationBuilder builder = new ConfigurationBuilder()
            .SetBasePath(basePath)
            .AddJsonFile(settingsFile);

        return builder.Build();
    }

    public static string GetConnectionString(string cxnName, string cfgFile = "connectionString.json")
    {
        IConfigurationRoot? root = LoadSettingsFile(cfgFile);
        string settings = root.GetConnectionString(cxnName);
        if (!string.IsNullOrEmpty(settings))
        {
            return settings;
        }
        throw new ConfigurationErrorsException($"Connection stirng {cxnName} not found in connection strings cfg file {cfgFile}.");
    }
    private static string FindBaseLocation(string settingsFile)
    {
        string?[] baseLocations =
        {
            Directory.GetCurrentDirectory(),
            AppDomain.CurrentDomain.BaseDirectory,
            Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location)
        };

        foreach (string? baseLocation in baseLocations)
        {
            if (string.IsNullOrEmpty(baseLocation))
                continue;
            string path = Path.Combine(baseLocation, settingsFile);
            if (File.Exists(path))
                return baseLocation;
        }

        return baseLocations[1]!;
    }

    public static T? GetSetting<T>(string key, bool mustExist)
    {
        return GetSetting(key, default(T), mustExist);
    }

    public static T? GetSetting<T>(string key, T? defaultValue = default)
    {
        return GetSetting(key, defaultValue, false);
    }

    public static T GetSetting<T>(string key, T defaultValue, bool mustExist)
    {
        string? valString = Environment.GetEnvironmentVariable(key);

        if (valString == null)
        {
            if (mustExist)
            {
                throw new ConfigurationErrorsException($"Setting {key} not found");
            }
            return defaultValue;
        }

        try
        {
            return (T)Convert.ChangeType(valString, typeof(T));
        }
        catch (Exception ex)
        {
            throw new ConfigurationErrorsException($"Settings {key} ('{valString}') cannot be converted to type {typeof(T).Name}", ex);
        }
    }
}