无法将 lambda 表达式转换为类型 "DbContextOptions <DataContext>"，因为它不是委托类型

Question

我创建了 class DataContect，它继承自 class IdentityDbContext:

using ProjDAL.Entities;
using ProjDAL.Relations;
using ProjDAL.Services;
using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Design;
using Microsoft.Extensions.Configuration;

namespace ProjDAL.EF
{
    public class DataContext : IdentityDbContext<ApplicationUser>
    {

        public DataContext(DbContextOptions<DataContext> options) : base(options)
        {
        }

        protected override void OnModelCreating(ModelBuilder builder)
        {
            base.OnModelCreating(builder);
        }
.......................................................
}

解决方案有控制台应用程序，我在其中创建了新的 DataContext：

using System;
using DbInitialize.Interface;
using ProjDAL.EF;

namespace DbInitialize.Provider 
{
    public class DbInitializeProvider : IDbInitialize
    {
        private DataContext _db;

        public DbInitializeProvider()
        {
            _db = new DataContext(options => options.UseSqlServer("Data Source=.\SQLEXPRESS;Initial Catalog=ProjAppTest;Integrated Security=True;MultipleActiveResultSets=true"));
        }

        public void SetCreateDatabase()
        {
            Console.WriteLine("Check for database availability: ");
            using (var transaction = _db.Database.BeginTransaction())
            {
                try {
                    if(_db.Database != null)
                    {
                        Console.WriteLine("Done!\r\n");
                    }
                    else
                    {
                        _db.Database.EnsureCreated();
                        Console.WriteLine("Database was created!\r\n");
                    }
                    transaction.Commit();
                }
                catch (DbException error)
                {
                    Console.WriteLine(error);
                    transaction.Rollback();
                }
            }
        }   
    }
}

我的 Program.cs 文件：

using System;
using DbInitialize.Provider;
using ProjDAL.EF;

namespace DbInitialize
{
    class Program
    {
        private static readonly DbInitializeProvider _db;
        delegate void Display();

        static Program()
        {
            _db = new DbInitializeProvider();
        }

        static void Main(string[] args)
        {
            try
            {
                Display display = _db.SetCreateDatabase;
                display.Invoke();

                Console.WriteLine($"\r\n{new string('-', 80)}");
                Console.WriteLine("For continue press any button...");
            }
            catch (Exception e)
            {
                Console.WriteLine(e);
            }
            Console.ReadLine();
        }
    }
}

我收到错误：无法将 lambda 表达式转换为类型 "DbContextOptions " 因为它不是委托类型 如何正确创建 DataContext 实例并设置选项参数？

如果您需要更多信息，请告诉我。谢谢你的帮助。

Answer 1

创建 DataContext class 时，参数与您在 DataContext 构造函数中定义的参数不匹配。它需要一个类型为 DbContextOptions<DataContext> 的对象，但您提供的操作带有选项参数 options => options.UseSqlServer("Data Source=.\SQLEXPRESS;Initial Catalog=ProjAppTest;Integrated Security=True;MultipleActiveResultSets=true")

您需要构建选项对象并将实例提供给构造函数：

var optionsBuilder = new DbContextOptionsBuilder<DataContext>();
optionsBuilder.UseSqlServer("YOUR CONNECTION STRING");

_db = new DataContext(optionsBuilder.Options)

或者您可以使用不带参数的构造函数，并在 DataContext class 的 OnConfiguring 方法中配置它。

在此处查看文档：https://docs.microsoft.com/en-us/ef/core/miscellaneous/configuring-dbcontext

无法将 lambda 表达式转换为类型 "DbContextOptions <DataContext>"，因为它不是委托类型

Cannot convert lambda expression to type "DbContextOptions <DataContext>" because it is not a delegate type

c#

asp.net-identity

entity-framework-core

.net-core