如何在.NETCore 3.1&中创建DbContextFactory开拓者

问题描述

我正在遵循有关如何设置EF Core使其在Blazor& amp; amp;中安全工作的准则..NET Core 3.1.MS文档在这里: https://docs.microsoft.com/zh-cn/aspnet/core/blazor/blazor-server-ef-core?view=aspnetcore-3.1

I'm following guidelines in how to setup EF Core to work safely in Blazor & .NET Core 3.1.The MS documentation is here: https://docs.microsoft.com/en-us/aspnet/core/blazor/blazor-server-ef-core?view=aspnetcore-3.1

在说明中，建议创建一个DbContextFactory，该工厂用于在每个服务中创建dbcontext.在Blazor的世界中一切都说得通，但代码无法像AddDbContextFactory不存在.如果在.Net Core 3.1/EF Core 3中还有另一种方法，我看不到.

In the instructions, advice is to create a DbContextFactory which is used to create a dbcontext in each service. All makes sense in the Blazor world, but the code won't compile asAddDbContextFactory does not exist. If there's another way to do it in .Net Core 3.1/ EF Core 3 - I can't see it.

services.AddDbContextFactory<ContactContext>(opt =>
    opt.UseSqlite($"Data Source={nameof(ContactContext.ContactsDb)}.db")
    .EnableSensitiveDataLogging());

推荐答案

我发现此扩展方法:

        public static IServiceCollection AddDbContextFactory<TContext>(
            this IServiceCollection collection,
            Action<DbContextOptionsBuilder> optionsAction = null,
            ServiceLifetime contextAndOptionsLifetime = ServiceLifetime.Singleton)
            where TContext : DbContext
        {
            // instantiate with the correctly scoped provider
            collection.Add(new ServiceDescriptor(
                typeof(IDbContextFactory<TContext>),
                sp => new DbContextFactory<TContext>(sp),
                contextAndOptionsLifetime));

            // dynamically run the builder on each request
            collection.Add(new ServiceDescriptor(
                typeof(DbContextOptions<TContext>),
                sp => GetOptions<TContext>(optionsAction, sp),
                contextAndOptionsLifetime));

            return collection;
        }

工厂类为此处:

    public class DbContextFactory<TContext> 
        : IDbContextFactory<TContext> where TContext : DbContext
    {
        private readonly IServiceProvider provider;

        public DbContextFactory(IServiceProvider provider)
        {
            this.provider = provider;
        }

        public TContext CreateDbContext()
        {
            if (provider == null)
            {
                throw new InvalidOperationException(
                    $"You must configure an instance of IServiceProvider");
            }

            return ActivatorUtilities.CreateInstance<TContext>(provider);
        }
    }

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