c# - 如何在 EF Core 中实例化 DbContext

Question

我还设置了 .net 核心项目和数据库上下文。但是由于这个错误，我还不能开始使用 dbContext-

"there is no argument given that corresponds to the required formalparameter 'options'"

Controller :

public IActionResult Index()
{
    using (var db = new BlexzWebDb())
    {

    }
    return View();
}

数据库上下文代码:

public class BlexzWebDb : DbContext
{
    public BlexzWebDb(DbContextOptions<BlexzWebDb> options)
       : base(options)
    { }

    public DbSet<User> Users { get; set; }
    public DbSet<Role> Roles { get; set; }
    public DbSet<AssignedRole> AssignedRoles { get; set; }
    
}

附上错误图片。如何解决此问题？

Answer 1

从ConnectionString实例化新的DbContext对象

var connectionstring = "Connection string";

var optionsBuilder = new DbContextOptionsBuilder<ApplicationDbContext>();
    optionsBuilder.UseSqlServer(connectionstring);


ApplicationDbContext dbContext = new ApplicationDbContext(optionsBuilder.Options);

// Or you can also instantiate inside using

using(ApplicationDbContext dbContext = new ApplicationDbContext(optionsBuilder.Options))
{
   //...do stuff
}