.net core 灵活读取配置文件

引用nuget

Microsoft.Extensions.Configuration
Microsoft.Extensions.Configuration.Binder
Microsoft.Extensions.Configuration.FileExtensions
Microsoft.Extensions.Configuration.EnvironmentVariables
Microsoft.Extensions.Configuration.Json

using Allspark.Core.Common.Json;
using Microsoft.Extensions.Configuration;
using System;
using System.Collections.Generic;
using System.IO;

namespace Allspark.Core.Common.Config
{
    public static class Configs
    {
        private const string DefaultConfigName = "appsettings.json";
        public class ConfigCache
        {
            internal static readonly IConfigurationRoot ConfigRoot = null;
            static ConfigCache()
            {
                try
                {
                    string pathToContentRoot = Directory.GetCurrentDirectory();

                    string configFilePath = Path.Combine(pathToContentRoot, DefaultConfigName);

                    if (!File.Exists(configFilePath))
                    {
                        throw new FileNotFoundException($"{DefaultConfigName}配置文件不存在！");
                    }
                    //用于构建基于键/值的配置设置，以便在应用程序中使用
                    IConfigurationBuilder builder = new ConfigurationBuilder()
                    .SetBasePath(pathToContentRoot)//将基于文件的提供程序的FileProvider设置为PhysicalFileProvider基本路径
                    .AddJsonFile(DefaultConfigName, optional: false, reloadOnChange: true)//在构建器的路径中添加JSON配置提供程序
                    .AddEnvironmentVariables();//添加读取的Microsoft.Extensions.Configuration.IConfigurationProvider来自环境变量的配置值 

                    ConfigRoot = builder.Build();

                }
                catch (Exception)
                {

                }
                finally
                {

                }
            }

        }
        /// <summary>
        /// 根据名称读取指定配置文件。若无法读取到数据，则使用defaultValue的值
        /// </summary>
        /// <typeparam name="T">节点的类型，可传对象</typeparam>
        /// <param name="name">配置文件节点名</param>
        /// <param name="defaultValue">默认值</param>
        /// <returns></returns>
        public static T Get<T>(string name, T defaultValue)
        {
            if (ConfigCache.ConfigRoot == null)
            {
                // throw new NullReferenceException("配置文件加载异常！"); 
                return defaultValue;
            }
            IConfigurationSection section = ConfigCache.ConfigRoot.GetSection(name);

            if (section == null)
            {
                throw new KeyNotFoundException($"{name}节点不存在！");
            }
            var config = section.Get<T>();
            if (config == null)
                return defaultValue;

            return config;
        }
        /// <summary>
        /// 根据名称读取指定配置文件
        /// </summary>
        /// <typeparam name="T">节点的类型，可传对象</typeparam>
        /// <param name="name">配置文件节点名</param>
        /// <returns></returns>
        public static T Get<T>(string name)
        {
            return Get<T>(name, default);
        }

        public static string Set<T>(string key, T value)
        {
            string StrValue = JsonHelper.ObjectToJson(value);
            IEnumerable<IConfigurationProvider> configProviders = ConfigCache.ConfigRoot.Providers;
            foreach (IConfigurationProvider item in configProviders)
            {
                if (item.TryGet(key, out string itemValue))
                {
                    item.Set(key, StrValue);
                    return StrValue;
                }
            }
            return "";
        }

    }
}