无法将Linq.IOrderedEnumerable <T>转换为Linq.IQueryable <T>

Question

尝试将orderby语句添加到我的通用存储库方法并获得以下错误.不知道为什么我似乎能够在其他情况下将.OrderBy添加到IQueryable.

我错过了什么？

得到错误:

无法将类型'System.Linq.IOrderedEnumerable'隐式转换为'System.Linq.IQueryable'

代码段(删除了一些部分):

public class QuickbooksRespository<TEntity>
         where TEntity : class, Intuit.Ipp.Data.IEntity, new()
    {
    public virtual IQueryable<TEntity> GetAll(
        int page, int pageSize,
        Func<TEntity, object> orderbyascending = null,
        Func<TEntity, object> orderbydescending = null)
    {
        int skip = Math.Max(pageSize * (page - 1), 0);

        IQueryable<TEntity> results = _qbQueryService
                .Select(all => all);

        if (orderbyascending != null)
        {
            results = results.OrderBy(orderbyascending);
        }

        if (orderbydescending != null)
        {
            results = results.OrderByDescending(orderbydescending);
        }

        return results
                .Skip(skip)
                .Take(pageSize);
    }
}

Answer 1

因为您提供Func<...>委托,IEnumerable.OrderBy所以选择了扩展方法.将方法参数更改为Expression<Func<...>>:

public virtual IQueryable<TEntity> GetAll(
    int page, int pageSize,
    Expression<Func<TEntity, object>> orderbyascending = null,
    Expression<Func<TEntity, object>> orderbydescending = null)

它将使IQueryable.OrderBy()方法被选择,而不是IEnumerable.OrderBy()在你OrderBy()以后实际调用时.