c# - ASP.NET Core 2 中的问题配置选项

Question

在我的项目上配置选项时，我遇到了这个错误:

System.InvalidOperationException: Could not create an instance of type 'Microsoft.Extensions.Options.IOptions`1[[myproject.Models.ConnectionStrings, ]'. Model bound complex types must not be abstract or value types and must have a parameterless constructor. Alternatively, give the 'optionsAccessor' parameter a non-null default value.

任何的想法 ？

我将模型配置如下:

namespace myproject.Models
{
  public class ConnectionStrings
  {
    public ConnectionStrings()
    {
        AzureStorageConnectionString = "azurestorageconnectionstring_ctor";
    }
    public string AzureStorageConnectionString { get; set; }
  }
}

Startup.cs ConfigureServices(IServiceCollection services) 包含以下两行

services.AddOptions();
services.Configure<ConnectionStrings>(Configuration.GetSection("ConnectionStrings"));

我的 Controller 包含这个

private ConnectionStrings _connectionStrings;
public IActionResult Index(IOptions<ConnectionStrings> optionsAccessor)
{
  _connectionStrings = optionsAccessor.Value;
  return View();
}

我的 appsettings.json 和 appsettings.Development.json 都包含以下

{
 "Logging": {
 "LogLevel": {
   "Default": "Debug",
   "System": "Information",
   "Microsoft": "Information"
  }
 },
 "ConnectionStrings": {
   "AzureStorageConnectionString": "xxxxxxxxx"
 },
}

Answer 1

你应该注入(inject) IOptions<ConnectionStrings>进入 Controller 的构造函数，而不是进入 Index()方法。

通过将其定义为操作参数，您期望 ModelBinder为您构建它(显然，它不能)。

见 Documentation