Question

尝试执行迁移时出现此错误

System.MissingMethodException：未定义无参数构造函数对于这个对象。在 System.RuntimeTypeHandle.CreateInstance（RuntimeType类型，布尔 publicOnly，布尔值wrapExceptions，布尔值和canBeCached， RuntimeMethodHandleInternal＆ctor）

我想做的是在dbcontext类中使用Iconfiguration。那有可能吗？这是我目前的操作方式：

public class AppDbContext : DbContext
{
    public IConfiguration Configuration { get; }
    public AppDbContext(DbContextOptions<AppDbContext> options,) : 
    base(options) { 
           Configuration = configuration;
    }
    public DbSet<ApplicationUsers> ApplicationUsers { get; set; }


    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.HasDefaultSchema(schema: Configuration["DatabaseConfiguration:SchemaName"]);
    }
}

Answer 1

请按照以下步骤实现您的要求：

修改AppDbContext

 public class AppDbContext : DbContext
{
     public IConfiguration Configuration { get; }
     public AppDbContext(DbContextOptions<AppDbContext> options, IConfiguration configuration) : 
     base(options) { 
            Configuration = configuration;
    }
    public DbSet<ApplicationUsers> ApplicationUsers { get; set; }


    protected override void OnModelCreating(ModelBuilder modelBuilder)
     {
       base.OnModelCreating(modelBuilder);
          modelBuilder.HasDefaultSchema(schema: Configuration["DatabaseConfiguration:SchemaName"]);
     }
     }

从Package Manager Console运行add-migration init
从Package Manager Console运行update-database

ASP.NET Core 2 System.MissingMethodException：没有为此对象定义无参数构造函数

1 个答案: