Error Translating Linq query whileselecting from group on Generic repository-CodePudding

I have the following method that is

public async Task<IList<TGroupSelect>> GetAll<TEntity,TGroup,TGroupSelect>(Func<IQueryable<T>, IIncludableQueryable<T, object>> include = null,
           Expression<Func<T, bool>> whereClause = null, Expression<Func<T, TEntity>> selector = null,

          Func<IQueryable<TEntity>, IQueryable<IGrouping<object, TEntity>>> groupBy = null,
          Func<IGrouping<object, TEntity>, TGroupSelect> groupSelector = null)
        {
            var result = _ctx.Set<T>().AsQueryable();

            result = include(result);

            var res = (whereClause is null ? result.Select(selector) : result.Where(whereClause).Select(selector));

           

            var group = groupBy(res);

            return  group.Select(groupSelector).ToList();
        }

on the last select it throws the following error

The LINQ expression 'DbSet<UserMeetings>()
    .Include(x => x.User)
    .Include(x => x.Meeting)
    .ThenInclude(x => x.Host)
    .Where(x => x.UserId == __UserId_0)
    .Select(x => x)
    .GroupBy(y => y.Meeting)' 

could not be translated. Either rewrite the query in a form that can
 be translated, or switch to client evaluation explicitly by inserting
 a call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or
 'ToListAsync'. 
See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.

so how can I make it work after the group by sentence without calling AsAsyncEnumerable?

here is how I used it


 var meetings =await  repo.GetAll<UserMeetings,Meeting, IGrouping<Meeting, UserMeetings>> (
                include:x=>x.Include(x=>x.User).Include(x=>x.Meeting).ThenInclude(x=>x.Host),
                whereClause: filter,
                selector: x=>x,
                groupBy: x => { return x.GroupBy(x => x.Meeting); }, 
                groupSelector:(x)=> x);

CodePudding user response：

Accourding to Microsoft documentation in .NET 5, GroupBy isn't translated to SQL query and you should use AsEnumerable or ToList before GroupBy statement.

Your code should be like this:

public async Task<IList<TGroupSelect>> GetAll<TEntity,TGroup,TGroupSelect>(Func<IQueryable<T>, IIncludableQueryable<T, object>> include = null,
          Expression<Func<T, bool>> whereClause = null, Expression<Func<T, TEntity>> selector = null,
          Func<IQueryable<TEntity>, IQueryable<IGrouping<object, TEntity>>> groupBy = null,
          Func<IGrouping<object, TEntity>, TGroupSelect> groupSelector = null)
{
    var result = _ctx.Set<T>().AsQueryable();

    result = include(result);

    var res = await (whereClause is null 
               ? result.Select(selector) 
               : result.Where(whereClause).Select(selector)
             ).ToListAsync();

    var group = groupBy(res);

    return  group.Select(groupSelector).ToList();
}