<ExtensionAttribute()>
Public Overloads Shared Function Contains( _
   ByVal source As IEntityScalarQuery, _
   ByVal item As Object, _
   Optional ByVal userCallback As Action(Of EntityScalarQueryOperation(Of Boolean)), _
   Optional ByVal userState As Object _
) As EntityScalarQueryOperation(Of Boolean)

Dim source As IEntityScalarQuery
Dim item As Object
Dim userCallback As Action(Of EntityScalarQueryOperation(Of Boolean))
Dim userState As Object
Dim value As EntityScalarQueryOperation(Of Boolean)
 
value = EntityScalarAsyncExtensions.Contains(source, item, userCallback, userState)

[ExtensionAttribute()]
public static EntityScalarQueryOperation<bool> Contains( 
   IEntityScalarQuery source,
   object item,
   Action<EntityScalarQueryOperation<bool>> userCallback,
   object userState
)

[ExtensionAttribute()]
public:
static EntityScalarQueryOperation<bool>^ Contains( 
   IEntityScalarQuery^ source,
   Object^ item,
   Action<EntityScalarQueryOperation<bool>^>^ userCallback,
   Object^ userState
) 

public void AsyncAny() {
  var op = _entityManager.Employees.AsScalarAsync().Any();
  op.Completed += (o, e) => {
    bool result = e.Result;
  }
}