.NET Core读取配置文件方式详细总结
基于.NET Core的跨平台开发，配置文件与之前.NET Framework采用xml的config文件不同，目前主要是采用json文件键值对配置方式读取。
参考网上相关资料总结如下：
一. 引入扩展 System.Configuration.ConfigurationManager
Nuget 下载扩展，Install-Package System.Configuration.ConfigurationManager
使用方式：添加配置文件App.config。读取方式与原.NET Framework方式一致
优点：兼容.NET Framework 原有配置方式
缺点：项目运行过程中若需修改App.config文件，对项目中输出的内容没有丝毫影响，Debug发现获取到的值的确没有变化，需要重新编译才生效。
二. 引入扩展 Microsoft.Extensions.Options.ConfigurationExtensions
Nuget 下载扩展，
Install-Package Microsoft.Extensions.Options.ConfigurationExtensions
Install-Package Microsoft.Extensions.Configuration.FileExtensions
Install-Package Microsoft.Extensions.Configuration.Json
使用方式：参考微软官网
优点：可以读取application.json中的配置参数，不再使用XML可以说很好的贴近Core的设计理念
缺点：运行时修改json文件读取到的内容不会改变，但是至少重启项目可以修改，若要运行时候修改json文件监听实现监听变化。查看源码，可以发现 虽然配置信息是通过AddSingleton注入的
但同时也注入了IOptionsChangeTokenSource ，故只需要在获取配置信息时将IOptions<> 替换为 IOptionsMonitor<>(通过监听的Option来获取信息)，并通过 IOptionsMonitor<>.CurrentValue获取即可实时获取到最新的配置信息(存在修改监听)
另外就是，这个方法采用的是反序列化的原理，也就是必须有一个跟配置文件对应的实体类才可以，这个感觉比较鸡肋，放弃。
三. 自定义扩展方法，这个实现自己写，原理是监听文件是否变更，来刷新Configuration 配置实现。
参考园友一个实现，具体需要是否有效，要花时间实践一下，原链接地址，代码如下：
复制代码
public class ConfigurationManager
{
/// <summary>
/// 配置内容
/// </summary>
private static NameValueCollection _configurationCollection = new NameValueCollection();
/// <summary>
/// 配置监听响应链堆栈
/// </summary>
private static Stack<KeyValuePair<string, FileSystemWatcher>> FileListeners = new Stack<KeyValuePair<string, FileSystemWatcher>>();
/// <summary>
/// 默认路径
/// </summary>
private static string _defaultPath = Directory.GetCurrentDirectory() + "\\appsettings.json";
/// <summary>
/// 最终配置文件路径
/// </summary>
private static string _configPath = null;
/// <summary>
/// 配置节点关键字
/// </summary>
private static string _configSection = "AppSettings";
/// <summary>
/// 配置外连接的后缀
/// </summary>
private static string _configUrlPostfix = "Url";
/// <summary>
/// 最终修改时间戳
/// </summary>
private static long _timeStamp = 0L;
/// <summary>
/// 配置外链关键词，例如：AppSettings.Url
/// </summary>
private static string _configUrlSection { get { return _configSection + "." + _configUrlPostfix; } }
static ConfigurationManager()
{
ConfigFinder(_defaultPath);
}
/// <summary>
/// 确定配置文件路径
/// </summary>
private static void ConfigFinder(string Path)
{
_configPath = Path;
JObject config_json = new JObject();
while (config_json != null)
{
config_json = null;
FileInfo config_info = new FileInfo(_configPath);
if (!config_info.Exists) break;
FileListeners.Push(CreateListener(config_info));
config_json = LoadJsonFile(_configPath);
if (config_json[_configUrlSection] != null)
_configPath = config_json[_configUrlSection].ToString();
else break;
}
if (config_json == null || config_json[_configSection] == null) return;
LoadConfiguration();
}
/// <summary>
/// 读取配置文件内容
/// </summary>
private static void LoadConfiguration()
{
FileInfo config = new FileInfo(_configPath);
var configColltion = new NameValueCollection();
JObject config_object = LoadJsonFile(_configPath);
if (config_object == null || !(config_object is JObject)) return;
if (config_object[_configSection]!=null)
{
foreach (JProperty prop in config_object[_configSection])
{
configColltion[prop.Name] = prop.Value.ToString();
}
}
_configurationCollection = configColltion;
}
/// <summary>
/// 解析Json文件
/// </summary>
/// <param name="FilePath">文件路径</param>
/// <returns></returns>
private static JObject LoadJsonFile(string FilePath)
{
JObject config_object = null;
try
{
StreamReader sr = new StreamReader(FilePath, Encoding.Default);
config_object = JObject.Parse(sr.ReadToEnd());
sr.Close();
}
catch { }
return config_object;
}
/// <summary>
/// 添加监听树节点
/// </summary>
/// <param name="info"></param>
/// <returns></returns>
private static KeyValuePair<string, FileSystemWatcher> CreateListener(FileInfo info)
{
FileSystemWatcher watcher = new FileSystemWatcher();
watcher.BeginInit();
watcher.Path = info.DirectoryName;
watcher.Filter = info.Name;
watcher.IncludeSubdirectories = false;
watcher.EnableRaisingEvents = true;
watcher.NotifyFilter = NotifyFilters.Attributes | NotifyFilters.CreationTime | NotifyFilters.DirectoryName | NotifyFilters.FileName | NotifyFilters.LastAccess | NotifyFilters.LastWrite | NotifyFilters.Size;
watcher.Changed += new FileSystemEventHandler(ConfigChangeListener);
watcher.EndInit();
return new KeyValuePair<string, FileSystemWatcher>(info.FullName, watcher);
}
private static void ConfigChangeListener(object sender, FileSystemEventArgs e)
{
long time = TimeStamp();
lock (FileListeners)
{
if (time > _timeStamp)
{
_timeStamp = time;
if (e.FullPath != _configPath || e.FullPath == _defaultPath)
{
while (FileListeners.Count > 0)
{
var listener = FileListeners.Pop();
listener.Value.Dispose();
if (listener.Key == e.FullPath) break;
}
ConfigFinder(e.FullPath);
}
else
{
LoadConfiguration();
}
}
}
}
private static long TimeStamp()
{
return (long)((DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalMilliseconds * 100);
}
private static string c_configSection = null;
public static string ConfigSection
{
get { return _configSection; }
set { c_configSection = value; }
}
private static string c_configUrlPostfix = null;
public static string ConfigUrlPostfix
{
get { return _configUrlPostfix; }
set { c_configUrlPostfix = value; }
}
private static string c_defaultPath = null;
public static string DefaultPath
{
get { return _defaultPath; }
set { c_defaultPath = value; }
}
public static NameValueCollection AppSettings
{
get { return _configurationCollection; }
}
/// <summary>
/// 手动刷新配置，修改配置后，请手动调用此方法，以便更新配置参数
/// </summary>
public static void RefreshConfiguration()
{
lock (FileListeners)
{
//修改配置
if (c_configSection != null) { _configSection = c_configSection; c_configSection = null; }
if (c_configUrlPostfix != null) { _configUrlPostfix = c_configUrlPostfix; c_configUrlPostfix = null; }
if (c_defaultPath != null) { _defaultPath = c_defaultPath; c_defaultPath = null; }
//释放掉全部监听响应链
while (FileListeners.Count > 0)
FileListeners.Pop().Value.Dispose();
ConfigFinder(_defaultPath);
}
}
}
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