SetBasePath的操作其实是在ConfigurationBuilder的属性字典里设置FileProvider的值。
public static IConfigurationBuilder SetBasePath(this IConfigurationBuilder builder, string basePath)
{
...
return builder.SetFileProvider(new PhysicalFileProvider(basePath));
}
public static IConfigurationBuilder SetFileProvider(this IConfigurationBuilder builder, IFileProvider fileProvider)
{
...
builder.Properties[FileProviderKey] = fileProvider ?? throw new ArgumentNullException(nameof(fileProvider));
return builder;
}
然后是添加JSON文件。
public static IConfigurationBuilder AddJsonFile(this IConfigurationBuilder builder, IFileProvider provider, string path, bool optional, bool reloadOnChange)
{
...
return builder.AddJsonFile(s =>
{
s.FileProvider = provider;
s.Path = path;
s.Optional = optional;
s.ReloadOnChange = reloadOnChange;
s.ResolveFileProvider();
});
}
public static IConfigurationBuilder AddJsonFile(this IConfigurationBuilder builder, Action<JsonConfigurationSource> configureSource)
=> builder.Add(configureSource);
ConfigurationBuilder里添加了一个JsonConfigurationSource对象。
最后，执行ConfigurationBuilder的Build方法，就可以得到保存配置信息的Configuration对象。
总结例子中的代码，获取配置信息的操作其实就分为两步:
- 生成Configuration对象
- 按键值从Configuration对象中获取信息
生成Configuration对象的步骤至少要有三个基础环节。
