在存储库中使用 Include() 方法 [英] Use Include() method in repository

问题描述

我在 EF 5 中有以下内容:

I have the following with EF 5:

var a = context.Posts.Include(x => x.Pack).Select(x => x.Pack.Id).ToList();

这有效.然后我尝试在我的通用存储库中复制它:

This works. Then I tried to replicate this in my generic repository:

public IQueryable<T> Include<T>(Expression<Func<T, Boolean>> criteria) where T : class
{
    return _context.Set<T>().Include(criteria);
}

但在这种情况下，我无法执行以下操作:

But in this case I am not able to do the following:

var b = repository.Include<Post>(x => x.Pack).Select(x => x.Pack.Id).ToList();

我收到错误:

无法将类型 'Data.Entities.Pack' 隐式转换为 'bool'

Cannot implicitly convert type 'Data.Entities.Pack' to 'bool'

我该如何解决这个问题?

How can I solve this?

我应该在我的 Include() 方法中更改什么?

What should I change in my Include() method?

推荐答案

尝试:

改变

Expression<Func<T, Boolean>> criteria

到

Expression<Func<T, object>> criteria

要包含多个实体，您需要添加一个包含"扩展名:

To Include multiple entities, you need to add an "include" extension:

public static class IncludeExtension
{
    public static IQueryable<TEntity> Include<TEntity>(this IDbSet<TEntity> dbSet,
                                            params Expression<Func<TEntity, object>>[] includes)
                                            where TEntity : class
    {
        IQueryable<TEntity> query = null;
        foreach (var include in includes)
        {
            query = dbSet.Include(include);
        }

        return query == null ? dbSet : query;
    }
}

然后你可以这样使用它:

Then you can use it like this:

repository.Include(x => x.Pack, x => x.Pack.Roles, ...).Select(x => x.Pack.Id).ToList();

只要确保repository"返回一个DbSet"对象.

Just make sure "repository" return a "DbSet" Object.

这篇关于在存储库中使用 Include() 方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！