Some services are not able to be constructed dbcontext

Question

Hi All,

I am migrating one asp.net core 3.1 from asp.net project. Here i have one dbcontext which connection string i need to pass from one of my appservice class. To use appservice, in this dbcontext i used something like below:

public class MyContext: DbContext
{
  private readonly IAppSetting _appSetting;

  public MyContext(IAppSetting appSetting) 
  {
      _appSetting = appSetting;
  }
  protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
  {
              optionsBuilder.UseSqlServer(_appSetting.Myconnectionstring, opts=> opts.CommandTimeout((int)TimeSpan.FromMinutes(1).TotalSeconds));
  }
}

In StartUp.cs file i have configure this context service like below:

public void ConfigureServices(IServiceCollection services)
{
  services.AddDbContext<MyContext>();
}

But when i run the application it is throwing runtime error like :

Some services are not able to be constructed dbcontext.

Need help.

Answer 1

Hi @Vikash Kumar Prasad ,

Based on your code (the MyContext class), when you create the MyContext instance you need call the constructor method and set the IAppSetting, you can refer the following sample:

In the following dbContext, I will set the connection string.

public class ApplicationDbContext : DbContext  
{   
    private readonly string _connectionString;  

    public ApplicationDbContext(string connectionString)  
    {  
        _connectionString = connectionString;  
    }  
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options)  
    {  
    }  
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)  
    {  
        optionsBuilder.UseSqlServer(_connectionString);  
    }  
    //tables  
}  

Then, in the ConfigureService method, register the service using AddSingleton() method, instead of the AddDbContext() method.

services.AddSingleton<ApplicationDbContext>(s=> new ApplicationDbContext(Configuration.GetConnectionString("DefaultConnection")));  

The result as below:

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Best regards,
Dillion

Answer 2

Maybe you should look into various ways to configure DBcontext in using dependency injection of the connection string.

https://learn.microsoft.com/en-us/ef/core/dbcontext-configuration/