.NET微服务应用中连接字符串返回空值的问题求助

问题现象 #

Chrome中抛出异常：

Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]
Unhandled exception rendering component: The argument namespaceConnectionString is null or white space. (Parameter 'namespaceConnectionString')

调试确认_config.GetConnectionString("AzureServiceBus")返回空值，项目配置文件Appsettings.json已配置对应节点，但服务类无法读取到连接字符串。

相关配置与代码 #

Appsettings.json配置：

{
  "ConnectionStrings": {
    "AzureServiceBus": "Endpoint=sb://abduservicebus.servicebus.windows.net/;SharedAccessKeyName=RootManageSharedAccessKey;SharedAccessKey=RandomChars="
  }
}

QueueService核心代码：

using Microsoft.Extensions.Configuration;
using Microsoft.Azure.ServiceBus;
using System.Text;
using System.Text.Json;

namespace SBSender.Services
{
    public class QueueService : IQueueService
    {
        private readonly IConfiguration _config;
        public QueueService(IConfiguration config)
        {
            _config = config;
        }
        public async Task SendMessageAsync<T>(T serviceBusMessage, string queueName)
        {
            var queueClient = new QueueClient(_config.GetConnectionString("AzureServiceBus"), queueName);
            string messageBody = JsonSerializer.Serialize(serviceBusMessage);
            Message message = new Message(Encoding.UTF8.GetBytes(messageBody));

            await queueClient.SendAsync(message);
        }
    }
}

Program.cs代码：

using Microsoft.AspNetCore.Components.Web;
using Microsoft.AspNetCore.Components.WebAssembly.Hosting;
using SBSender;
using SBSender.Services;

var builder = WebAssemblyHostBuilder.CreateDefault(args);
builder.RootComponents.Add<App>("#app");
builder.RootComponents.Add<HeadOutlet>("head::after");

builder.Services.AddScoped(sp => new HttpClient { BaseAddress = new Uri(builder.HostEnvironment.BaseAddress) });
builder.Services.AddTransient<IQueueService, QueueService>();

await builder.Build().RunAsync();

排查与解决步骤 #

• 检查配置文件属性：右键Appsettings.json文件→属性，将「复制到输出目录」设置为「如果较新则复制」或「始终复制」。WebAssembly项目中配置文件需被复制到输出目录才能被运行时读取。
• 验证配置读取路径：替换GetConnectionString方式，直接通过键路径读取验证：

  var connectionString = _config["ConnectionStrings:AzureServiceBus"];
  

  若该方式能获取到值，说明GetConnectionString匹配异常，可直接使用此方式读取。
• 排查环境配置覆盖：如果存在appsettings.Development.json等环境特定配置文件，确认其中未清空或覆盖ConnectionStrings节点。
• 显式加载配置文件：在Program.cs中显式指定加载配置文件，确保配置被正确加载：

  builder.Configuration.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true);
  

• 迁移至新版SDK：当前使用的Microsoft.Azure.ServiceBus为旧版SDK，建议替换为Azure.Messaging.ServiceBus，新版API更稳定且配置读取逻辑更可靠，示例代码如下：

  using Azure.Messaging.ServiceBus;
  using Microsoft.Extensions.Configuration;
  using System.Text.Json;
  
  namespace SBSender.Services
  {
      public class QueueService : IQueueService
      {
          private readonly IConfiguration _config;
          public QueueService(IConfiguration config)
          {
              _config = config;
          }
          public async Task SendMessageAsync<T>(T serviceBusMessage, string queueName)
          {
              var connectionString = _config.GetConnectionString("AzureServiceBus");
              await using var client = new ServiceBusClient(connectionString);
              ServiceBusSender sender = client.CreateSender(queueName);
              
              string messageBody = JsonSerializer.Serialize(serviceBusMessage);
              var message = new ServiceBusMessage(messageBody);
              
              await sender.SendMessageAsync(message);
          }
      }
  }
  

内容的提问来源于stack exchange，提问作者Vaclemor