如何在Blazor服务器中访问appsettings.json数据

Question

我正试图访问我的blazor服务器应用程序中后台服务中存储在appsettings.json文件中的数据，但大多数关于如何在线访问的说明都是基于blazor的Webassembly配置。我想我应该使用Microsoft.Extensions.Configuration包，但我不太清楚如何实现它

下面是带有基本代码的后台服务

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Linq;
using System.Text.Json;
using System.Threading.Tasks;
using System.Timers;
using log4net;
using System.Net;
using System.IO;
using System.Data.SqlClient;
using Microsoft.Extensions.Configuration;
namespace BlazorServerApp
{
public class JobExecutedEventArgs : EventArgs { }
public class PeriodicExecutor : IDisposable
{
Timer _Timer;
bool _Running;
public void StartExecuting()
{
if (!_Running)
{
// Initiate a Timer
_Timer = new Timer();
_Timer.Interval = 5000;
_Timer.Elapsed += HandleTimer;
_Timer.AutoReset = true;
_Timer.Enabled = true;
_Running = true;
}
}
void HandleTimer(object source, ElapsedEventArgs e)
{
// Execute required job
//connect to the appropriate SQL database
var connectionString = "connection";
//create connection variables for the two main SQL operations we will be doing
using var connectionUpdate = new SqlConnection(connectionString);
using var connectionCreate = new SqlConnection(connectionString);
while (true)
{
Parallel.Invoke(
() => createSurveyQueueEntries(connectionCreate),
() => updateSurveyQueue(connectionUpdate));
}
// Notify any subscribers to the event
OnJobExecuted();
}
public void Dispose()
{
if (_Running)
{
_Timer?.Dispose();
}
}
}
}

我想使用appsetting.json中定义的connectionString，并使用它来设置HandleTimer()方法中的connectionString变量。

下面是appsettings.json文件

{
"connectionString": "connection",
"Logging": {
"LogLevel": {
"Default": "Information",
"Microsoft": "Warning",
"Microsoft.Hosting.Lifetime": "Information"
}
},
"AllowedHosts": "*"
}

如有任何详细指导，我们将不胜感激。

Answer 1

如果您在某个类中工作，例如创建服务，则需要在constructure:中添加IConfiguration

using Microsoft.Extensions.Configuration;
private readonly IConfiguration configuration;
public PeriodicExecutor(IConfiguration configuration)
{             
this.configuration = configuration;
}
//Then you can use it 
var connection=  configuration["connectionString"];

如果你有razor组件，那么你需要像这样Inject IConfiguration：

using Microsoft.Extensions.Configuration;
[Inject]
private IConfiguration configuration { get; set; }
//then you can get your connectionString
var connection=  configuration["connectionString"];

你可以阅读更多关于这个

Answer 2

除上述解决方案外，以下解决方案也适用：首先安装此软件包：

using Microsoft.Extensions.Configuration;

然后在类的顶部添加以下代码行：

private static readonly IConfiguration config = new ConfigurationBuilder().AddJsonFile("appsettings.json").AddEnvironmentVariables().Build(); 

然后你可以使用这样的密钥访问存储的数据：

var connectionString = config.GetValue<string>("keyname");

有关详细信息，请查看以下链接：https://learn.microsoft.com/en-us/dotnet/core/extensions/configuration