Enumerable.SelectMany<TSource, TResult> Method (IEnumerable<TSource>, Func<TSource, Int32, IEnumerable<TResult>>)

Type Parameters

• TSource
  The type of the elements of source.

• TResult
  The type of the elements of the sequence returned by selector.

Parameters

• source
  Type: System.Collections.Generic.IEnumerable<TSource>
  A sequence of values to project.

• selector
  Type: System.Func<TSource, Int32, IEnumerable<TResult>>
  A transform function to apply to each source element; the second parameter of the function represents the index of the source element.

Return Value

Type: System.Collections.Generic.IEnumerable<TResult>
An IEnumerable<T> whose elements are the result of invoking the one-to-many transform function on each element of an input sequence.

Structure PetOwner
   Public Name As String
   Public Pets() As String
End Structure

Sub SelectManyEx2()
   ' Create an array of PetOwner objects.
   Dim petOwners() As PetOwner = _
       {New PetOwner With _
        {.Name = "Higa, Sidney", .Pets = New String() {"Scruffy", "Sam"}}, _
        New PetOwner With _
        {.Name = "Ashkenazi, Ronen", .Pets = New String() {"Walker", "Sugar"}}, _
        New PetOwner With _
        {.Name = "Price, Vernette", .Pets = New String() {"Scratches", "Diesel"}}, _
        New PetOwner With _
        {.Name = "Hines, Patrick", .Pets = New String() {"Dusty"}}}

   ' Project the items in the array by appending the index 
   ' of each PetOwner to each pet's name in that petOwner's 
   ' array of pets.
   Dim query As IEnumerable(Of String) = _
       petOwners.SelectMany(Function(petOwner, index) _
                                petOwner.Pets.Select(Function(pet) _
                                                         index.ToString() + pet))

   Dim output As New System.Text.StringBuilder
   For Each pet As String In query
      output.AppendLine(pet)
   Next

   ' Display the output.
   outputBlock.Text &= output.ToString() & vbCrLf
End Sub

      class PetOwner
      {
         public string Name { get; set; }
         public List<string> Pets { get; set; }
      }

      public static void SelectManyEx2()
      {
         PetOwner[] petOwners = 
                 { new PetOwner { Name="Higa, Sidney", 
                       Pets = new List<string>{ "Scruffy", "Sam" } },
                   new PetOwner { Name="Ashkenazi, Ronen", 
                       Pets = new List<string>{ "Walker", "Sugar" } },
                   new PetOwner { Name="Price, Vernette", 
                       Pets = new List<string>{ "Scratches", "Diesel" } },
                   new PetOwner { Name="Hines, Patrick", 
                       Pets = new List<string>{ "Dusty" } } };

         // Project the items in the array by appending the index 
         // of each PetOwner to each pet's name in that petOwner's 
         // array of pets.
         IEnumerable<string> query =
             petOwners.SelectMany((petOwner, index) =>
                                      petOwner.Pets.Select(pet => index + pet));

         foreach (string pet in query)
         {
            outputBlock.Text += pet + "\n";
         }
      }

      // This code produces the following output:
      //
      // 0Scruffy
      // 0Sam
      // 1Walker
      // 1Sugar
      // 2Scratches
      // 2Diesel
      // 3Dusty