C# Linq Group By on multiple columns
var consolidatedChildren =
from c in children
group c by new
{
c.School,
c.Friend,
c.FavoriteColor,
} into gcs
select new ConsolidatedChild()
{
School = gcs.Key.School,
Friend = gcs.Key.Friend,
FavoriteColor = gcs.Key.FavoriteColor,
Children = gcs.ToList(),
};
var consolidatedChildren =
children
.GroupBy(c => new
{
c.School,
c.Friend,
c.FavoriteColor,
})
.Select(gcs => new ConsolidatedChild()
{
School = gcs.Key.School,
Friend = gcs.Key.Friend,
FavoriteColor = gcs.Key.FavoriteColor,
Children = gcs.ToList(),
});
Given a list:
var list = new List<Child>()
{
new Child()
{School = "School1", FavoriteColor = "blue", Friend = "Bob", Name = "John"},
new Child()
{School = "School2", FavoriteColor = "blue", Friend = "Bob", Name = "Pete"},
new Child()
{School = "School1", FavoriteColor = "blue", Friend = "Bob", Name = "Fred"},
new Child()
{School = "School2", FavoriteColor = "blue", Friend = "Fred", Name = "Bob"},
};
The query would look like:
var newList = list
.GroupBy(x => new {x.School, x.Friend, x.FavoriteColor})
.Select(y => new ConsolidatedChild()
{
FavoriteColor = y.Key.FavoriteColor,
Friend = y.Key.Friend,
School = y.Key.School,
Children = y.ToList()
}
);
Test code:
foreach(var item in newList)
{
Console.WriteLine("School: {0} FavouriteColor: {1} Friend: {2}", item.School,item.FavoriteColor,item.Friend);
foreach(var child in item.Children)
{
Console.WriteLine("\t Name: {0}", child.Name);
}
}
Result:
School: School1 FavouriteColor: blue Friend: Bob
Name: John
Name: Fred
School: School2 FavouriteColor: blue Friend: Bob
Name: Pete
School: School2 FavouriteColor: blue Friend: Fred
Name: Bob