I've been using 101 LINQ Samples to get my feet wet using LINQ. It's been a good first resource, but I can't see an example there of what I currently need.
I just need to associate a sequential group number with each group. I have a working solution:
var groups =
from c in list
group c by c.Name into details
select new { Name = details.Key, DetailRecords = details };
int groupNumber = 0;
foreach (var group in groups)
{
//
// process each group and it's records ...
//
groupNumber++;
}
But, I'm sure it's possible to use LINQ to also generate the groupNumber. How?
The Linq GroupBy in C# belongs to the Grouping Operators category and exactly does the same thing as the Group By clause does in SQL Query. This method takes a flat sequence of elements and then organizes the elements into groups (i.e. IGrouping<TKey, TSource>) based on a given key.
You can also use Into Group with GroupBy in VB.Net. LINQ query is ended with the help Select or Groupby clause. It can also support method syntax in both C# and VB.Net languages.
A LINQ query can end with a GroupBy or Select clause. The result of GroupBy operators is a collection of groups. For example, GroupBy returns IEnumerable<IGrouping<TKey,Student>> from the Student collection: Return type of GroupBy()
The GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) method returns a collection of IGrouping<TKey,TElement> objects, one for each distinct key that was encountered.
This depends on your exact needs, but you can use:
var groupArray = groups.ToArray();
Similarly, you can use ToList
. These data structures are sequential, and each group has an index.
If you do need the index on the object you create, another option is to use Select
:
list.GroupBy(c => c.Name)
.Select((details, ind) =>
new
{
Name = details.Key,
DetailRecords = details,
Index = ind
});
this should do the trick:
int groupNumber = 0;
var groups =
from c in list
group c by c.Name into details
select new { Name = details.Key, DetailRecords = details, grpNum = groupNumber++};
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