除了 dbContext 之外，如何向 Blazor 中的服务添加参数？

Posted 2023-02-16

【中文标题】除了 dbContext 之外，如何向 Blazor 中的服务添加参数？

【英文标题】：How to add a parameter to a service in Blazor in addition to the dbContext?

【发布时间】：2022-01-10 00:39:43

【问题描述】：

VS2022 NetCore 6 EF 6

    builder.Services.AddDbContext<MyAppDbContext>(options removed for simplicity)

    //This is my service registered on Program.cs:
    builder.Services.AddScoped<AccountService>();
    
    //This is the existing class that works as expected:
    public class AccountService
    
     private readonly MyAppDbContext _context;  
     public AccountService(MyAppDbContext context)
       
          _context = context;
       
    
    //So far so good... 
    
    // Now I need to add another parameter to the service:
    public class AccountService
    
     private readonly MyAppDbContext _context;  
     public AccountService(MyAppDbContext context, string newParameter)
       
          _context = context;
          string temp = newParameter;
       
    
    
    // But I cannot register; I don't know what to put as first value and if I put MyAppDbContext it gives an error saying it is a type.
    
    builder.Services.AddScoped(ServiceProvider =>  return new AccountService(??, newParameter););

// This works (no compile error) for newParameter but ignores DbContext
    builder.Services.AddScoped(ServiceProvider =>  return new AccountService( **null**, newParameter););

【问题讨论】：

查看这个类似问题的答案：***.com/questions/53884417/…

我做到了。我用参数创建服务没有问题。我的问题是我不知道如何将第一个作为 dbContext 传递。请查看已编辑的问题

【参考方案1】：

你的注册会变得有点丑：

builder.Services.AddScoped<AccountService>(x => new AccountService( 
     x.GetRequiredService<MyAppDbContext>(),
     newParameter));

每次您需要 AccountService 时，让 ServiceProvider 创建（作用域）DbContext 很重要。