public static IGroupByManyResult <T> GroupByMany <T>(this IEnumerable <T> source, IEqualityComparer <object> equalityComparer, params Expression <Func <T, object> >[] keySelectors)
{
var groups = GroupByMany(string.Empty, source, equalityComparer, keySelectors).ToList();
var group = new GroupByManyResult <T>(groups)
{
Key = string.Empty,
Count = groups.Count,
Details = groups.SelectMany(g => g.Details)
};
foreach (var subGroup in groups)
{
subGroup.Parent = group;
}
return(group);
}
private static List <GroupByManyResult <T> > GroupByMany <T>(string parentKey, IEnumerable <T> source,
IEqualityComparer <object> equalityComparer, params Expression <Func <T, object> >[] keySelectors)
{
if (!keySelectors.Any())
{
return(new List <GroupByManyResult <T> >());
}
var curSelector = keySelectors.First();
var nextSelectors = keySelectors.Skip(1).ToArray();
var index = 0;
var results = new List <GroupByManyResult <T> >();
var groupName = GetName(curSelector);
var compiled = curSelector.Compile();
foreach (var group in source
.GroupBy(compiled, equalityComparer)
.Where(g => g.Key != null))
{
var key = string.IsNullOrEmpty(parentKey) ? index++.ToString() : $"{parentKey}-{index++}";
var subGroups = GroupByMany(key, group, equalityComparer, nextSelectors);
var result = new GroupByManyResult <T>(subGroups)
{
Key = key,
GroupName = groupName,
Item = group.Key,
Count = group.Count(),
Details = group,
FirstDetail = group.FirstOrDefault(),
};
foreach (var subGroup in subGroups)
{
subGroup.Parent = result;
}
results.Add(result);
}
return(results);
}