IGrouping<TKey,TElement>.Key Property

Definition

Namespace:

System.Linq

Assemblies:

netstandard.dll, System.Linq.dll

Gets the key of the IGrouping<TKey,TElement>.

C#

public TKey Key { get; }

Property Value

TKey

The key of the IGrouping<TKey,TElement>.

Examples

The following example demonstrates how to use the Key property to label each IGrouping<TKey,TElement> object in a sequence of IGrouping<TKey,TElement> objects. The GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) method is used to obtain a sequence of IGrouping<TKey,TElement> objects. The foreach in Visual C# or For Each in Visual Basic loop then iterates through each IGrouping<TKey,TElement> object, outputting its key and the number of values it contains.

C#

// Get a sequence of IGrouping objects.
IEnumerable<IGrouping<System.Reflection.MemberTypes, System.Reflection.MemberInfo>> memberQuery =
    typeof(String).GetMembers().
    GroupBy(member => member.MemberType);

// Output the key of each IGrouping object and the count of values.
foreach (IGrouping<System.Reflection.MemberTypes, System.Reflection.MemberInfo> group in memberQuery)
    Console.WriteLine("(Key) {0} (Member count) {1}", group.Key, group.Count());

// The output is similar to:
// (Key) Method (Member count) 113
// (Key) Constructor (Member count) 8
// (Key) Property (Member count) 2
// (Key) Field (Member count) 1

Remarks

The key of an IGrouping<TKey,TElement> represents the attribute that is common to each value in the IGrouping<TKey,TElement>.

Applies to