How to create DbContext - asp.net-core

Question

below default code in controller working fine
public ProductController(appDbContext parmContext)
{
_context = parmContext;
}
now I want to add DAL and in that, getting error creating object of type appDbContext, what to pass/set for parmContext?
below is the connection in Startup.cs
public void ConfigureServices(IServiceCollection services)
{
services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
services.AddDbContext<appDbContext>(config =>
{
config.UseMySql(Configuration.GetConnectionString("PreSales"));
});
}
Below is the code I want to use
public IEnumerable<ProductStatusMaster> GetProductStatusFRdal()
// here I ant to create object of DBcontext (i.e. _context)
{
try
{
var msm = _context.ProductStatusMaster
.Where(s => s.ActiveYn == 1 )
.OrderBy(s => s.Status)
.ToList();
return msm;
}
catch
{
throw;
}
}

Answer 1

Let me get an answer.
There are 2 ways to realize code you want.
1) Through Controller DI.
2) Through Service Locator pattern (antipattern).
By the code:
public void ConfigureServices(IServiceCollection services)
{
services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
services.AddDbContext<appDbContext>(config =>
{
config.UseMySql(Configuration.GetConnectionString("PreSales"));
});
}
you set up dependency for DbContext and configure connection parameters. So, for the first method you should pass the dependency through controller. Possible code will be like this:
public class MyTestAppController
{
private appDbContext _context;
public MyTestApController(appDbContext externalAppDbContext)
{
_context = externalAppDbContext;
}
public IEnumerable<ProductStatusMaster> GetProductStatusFRdal()
{
try
{
var msm = _context.ProductStatusMaster
.Where(s => s.ActiveYn == 1 )
.OrderBy(s => s.Status)
.ToList();
return msm;
}
catch
{
throw;
}
}
}
2) Using Service Locator pattern
In this case you should use IServiceProvider dependency. Code example like this:
public class MyTestAppController
{
private IServiceProvider _provider;
public MyTestAppController(IServiceProvider provider) => _provider = provider;
public IEnumerable<ProductStatusMaster> GetProductStatusFRdal()
{
var _context = _provider.GetService<appDbContext>();
try
{
var msm = _context.ProductStatusMaster .Where(s => s.ActiveYn == 1 )
.OrderBy(s => s.Status) .ToList(); return msm;
}
catch { throw; }
}
}