以下程序:
using System;
using System.Collections.Generic;
using Microsoft.Extensions.Configuration;
namespace ConsoleApp3
{
class Program
{
static void Main()
{
var builder = new ConfigurationBuilder();
builder.AddJsonFile("appsettings.json");
var configuration = builder.Build();
var options = configuration.Get<Options>();
foreach (var kvp in options.Values)
Console.WriteLine($"{kvp.Key}: {kvp.Value}");
}
}
internal class Options
{
public Dictionary<string, bool> Values { get; } = new Dictionary<string, bool>();
}
}
当给出这个appsettings.json
文件时,运行完美:
{
"Values": {
"a": true,
"b": false
}
}
但将appsettings.json
内容更改为:
{
"Values": {
"a:b": true,
"b": false
}
}
我得到这个例外:
未处理的异常:System.InvalidOperationException:无法创建类型为“System.Boolean”的实例,因为它缺少公共无参数构造函数。
堆栈跟踪:
at Microsoft.Extensions.Configuration.ConfigurationBinder.CreateInstance(Type type)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindInstance(Type type, Object instance, IConfiguration config, BinderOptions options)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindDictionary(Object dictionary, Type dictionaryType, IConfiguration config, BinderOptions options)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindInstance(Type type, Object instance, IConfiguration config, BinderOptions options)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindProperty(PropertyInfo property, Object instance, IConfiguration config, BinderOptions options)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindNonScalar(IConfiguration configuration, Object instance, BinderOptions options)
at Microsoft.Extensions.Configuration.ConfigurationBinder.BindInstance(Type type, Object instance, IConfiguration config, BinderOptions options)
at Microsoft.Extensions.Configuration.ConfigurationBinder.Get[T](IConfiguration configuration, Action`1 configureOptions)
at ConsoleApp3.Program.Main() in D:\Dev\ConsoleApp3\ConsoleApp3\Program.cs:line 15
我究竟做错了什么?请注意,在键中使用冒号是完全合法的json,但是不支持在appsettings.json文件中存储任何奇怪的字典?
参考Configuration in ASP.NET Core: Hierarchical configuration data
Configuration API能够通过在配置键中使用分隔符来展平分层数据来维护分层配置数据。
将文件读入配置时,会创建唯一键以维护配置源的原始分层数据结构。使用冒号(:)来平滑部分和键以保持原始结构
这意味着在以下appsettings.json文件中
{
"Values": {
"a:b": true,
"b": false
}
}
钥匙将被夷为平地
当ConfigurationBinder.BindDictionary
试图绑定Dictionary<string, bool>
中的Options
属性时,它会打破设置文件的结构
同时参考这个GitHub Issue
冒号保留用于键中的特殊含义,因此不应将它们用作普通键值的一部分。