/// <summary> 
    /// 配置信息 
     /// </summary> 
    public IConfigurationRoot Configuration { get; set; }

    /// <summary> 
    /// 程序入口点 
    /// </summary> 
    /// <param name="env"></param> 
    public Startup(IHostingEnvironment env) 
    { 
        var builder = new ConfigurationBuilder() 
                     .AddJsonFile("appsettings.json") 
                     .AddEnvironmentVariables(); 
        Configuration = builder.Build(); 
    }

    /// <summary>
    /// Represents a set of key/value application configuration properties.
    /// </summary>
    public interface IConfiguration
    {
        /// <summary>
        /// Gets or sets a configuration value.
        /// </summary>
        /// <param name="key">The configuration key.</param>
        /// <returns>The configuration value.</returns>
        string this[string key] { get; set; }

        /// <summary>
        /// Gets a configuration sub-section with the specified key.
        /// </summary>
        /// <param name="key">The key of the configuration section.</param>
        /// <returns>The <see cref="IConfigurationSection"/>.</returns>
        /// <remarks>
        ///     This method will never return <c>null</c>. If no matching sub-section is found with the specified key,
        ///     an empty <see cref="IConfigurationSection"/> will be returned.
        /// </remarks>
        IConfigurationSection GetSection(string key);

        /// <summary>
        /// Gets the immediate descendant configuration sub-sections.
        /// </summary>
        /// <returns>The configuration sub-sections.</returns>
        IEnumerable<IConfigurationSection> GetChildren();

        IChangeToken GetReloadToken();
    }

       var configurationBuilder = new ConfigurationBuilder();
       configurationBuilder.AddIniFile(_iniConfigFilePath);
       configurationBuilder.AddJsonFile(_jsonConfigFilePath);
       configurationBuilder.AddXmlFile(_xmlConfigFilePath);
       configurationBuilder.AddInMemoryCollection(_memConfigContent);
       var config = configurationBuilder.Build();

        /// <summary>
        /// Adds the JSON configuration provider at <paramref name="path"/> to <paramref name="configurationBuilder"/>.
        /// </summary>
        /// <param name="configurationBuilder">The <see cref="IConfigurationBuilder"/> to add to.</param>
        /// <param name="path">Absolute path or path relative to <see cref="IConfigurationBuilder.BasePath"/> of
        /// <paramref name="configurationBuilder"/>.</param>
        /// <param name="optional">Determines if loading the configuration provider is optional.</param>
        /// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
        /// <exception cref="ArgumentException">If <paramref name="path"/> is null or empty.</exception>
        /// <exception cref="FileNotFoundException">If <paramref name="optional"/> is <c>false</c> and the file cannot
        /// be resolved.</exception>
        public static IConfigurationBuilder AddJsonFile(
            this IConfigurationBuilder configurationBuilder,
            string path,
            bool optional)
        {
            if (configurationBuilder == null)
            {
                throw new ArgumentNullException(nameof(configurationBuilder));
            }

            if (string.IsNullOrEmpty(path))
            {
                throw new ArgumentException(Resources.Error_InvalidFilePath, nameof(path));
            }

            var fullPath = Path.Combine(configurationBuilder.GetBasePath(), path);

            if (!optional && !File.Exists(fullPath))
            {
                throw new FileNotFoundException(Resources.FormatError_FileNotFound(fullPath), fullPath);
            }

            configurationBuilder.Add(new JsonConfigurationProvider(fullPath, optional: optional));

            return configurationBuilder;
        }