Enumerable.ToDictionary<TSource, TKey> Method (IEnumerable<TSource>, Func<TSource, TKey>)

Type Parameters

• TSource
  The type of the elements of source.

• TKey
  The type of the key returned by keySelector.

Parameters

• source
  Type: System.Collections.Generic.IEnumerable<TSource>
  An IEnumerable<T> to create a Dictionary<TKey, TValue> from.

• keySelector
  Type: System.Func<TSource, TKey>
  A function to extract a key from each element.

Return Value

Type: System.Collections.Generic.Dictionary<TKey, TSource>
A Dictionary<TKey, TValue> that contains keys and values.

   Structure Package
      Public Company As String
      Public Weight As Double
      Public TrackingNumber As Long
   End Structure

   Sub ToDictionaryEx1()
      ' Create a list of Package values.
      Dim packages As New List(Of Package)(New Package() _
           {New Package With _
            {.Company = "Coho Vineyard", .Weight = 25.2, .TrackingNumber = 89453312L}, _
            New Package With _
            {.Company = "Lucerne Publishing", .Weight = 18.7, .TrackingNumber = 89112755L}, _
            New Package With _
            {.Company = "Wingtip Toys", .Weight = 6.0, .TrackingNumber = 299456122L}, _
            New Package With _
            {.Company = "Adventure Works", .Weight = 33.8, .TrackingNumber = 4665518773L}})

      ' Create a Dictionary that contains Package values, 
      ' using TrackingNumber as the key.
      Dim dict As Dictionary(Of Long, Package) = _
          packages.ToDictionary(Function(p) p.TrackingNumber)

      ' Display the results.
      Dim output As New System.Text.StringBuilder
      For Each kvp As KeyValuePair(Of Long, Package) In dict
         output.AppendLine("Key " & kvp.Key & ": " & _
                           kvp.Value.Company & ", " & _
                           kvp.Value.Weight & " pounds")
      Next
      outputBlock.Text &= output.ToString() & vbCrLf
   End Sub

   ' This code produces the following output:
   '
   ' Key 89453312: Coho Vineyard, 25.2 pounds
   ' Key 89112755: Lucerne Publishing, 18.7 pounds
   ' Key 299456122: Wingtip Toys, 6 pounds
   ' Key 4665518773: Adventure Works, 33.8 pounds

      class Package
      {
         public string Company { get; set; }
         public double Weight { get; set; }
         public long TrackingNumber { get; set; }
      }

      public static void ToDictionaryEx1()
      {
         List<Package> packages =
             new List<Package>
                     { new Package { Company = "Coho Vineyard", Weight = 25.2, TrackingNumber = 89453312L },
                       new Package { Company = "Lucerne Publishing", Weight = 18.7, TrackingNumber = 89112755L },
                       new Package { Company = "Wingtip Toys", Weight = 6.0, TrackingNumber = 299456122L },
                       new Package { Company = "Adventure Works", Weight = 33.8, TrackingNumber = 4665518773L } };

         // Create a Dictionary of Package objects, 
         // using TrackingNumber as the key.
         Dictionary<long, Package> dictionary =
             packages.ToDictionary(p => p.TrackingNumber);

         foreach (KeyValuePair<long, Package> kvp in dictionary)
         {
            outputBlock.Text += String.Format(
                "Key {0}: {1}, {2} pounds",
                kvp.Key,
                kvp.Value.Company,
                kvp.Value.Weight) + "\n";
         }
      }

      /*
       This code produces the following output:

       Key 89453312: Coho Vineyard, 25.2 pounds
       Key 89112755: Lucerne Publishing, 18.7 pounds
       Key 299456122: Wingtip Toys, 6 pounds
       Key 4665518773: Adventure Works, 33.8 pounds
      */