/// <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;

        }