Enumerable.Count<TSource> Method (IEnumerable<TSource>, Func<TSource, Boolean>)

Type Parameters

• TSource
  The type of the elements of source.

Parameters

• source
  Type: System.Collections.Generic.IEnumerable<TSource>
  A sequence that contains elements to be tested and counted.

• predicate
  Type: System.Func<TSource, Boolean>
  A function to test each element for a condition.

Return Value

Type: System.Int32
A number that represents how many elements in the sequence satisfy the condition in the predicate function.

   Structure Pet
      Public Name As String
      Public Vaccinated As Boolean
   End Structure

   Sub CountEx2()
      ' Create an array of Pet objects.
      Dim pets() As Pet = {New Pet With {.Name = "Barley", .Vaccinated = True}, _
                           New Pet With {.Name = "Boots", .Vaccinated = False}, _
                           New Pet With {.Name = "Whiskers", .Vaccinated = False}}

      Try
         ' Count the number of Pets in the array where the Vaccinated property is False.
         Dim numberUnvaccinated As Integer = _
             pets.Count(Function(p) p.Vaccinated = False)
         ' Display the output.
         outputBlock.Text &= "There are " & numberUnvaccinated & " unvaccinated animals." & vbCrLf
      Catch e As OverflowException
         outputBlock.Text &= "The count is too large to store as an Int32. Try using LongCount() instead." & vbCrLf
      End Try

   End Sub

   ' This code produces the following output:
   '
   ' There are 2 unvaccinated animals.

      class Pet
      {
         public string Name { get; set; }
         public bool Vaccinated { get; set; }
      }

      public static void CountEx2(System.Windows.Controls.TextBlock outputBlock)
      {
         Pet[] pets = { new Pet { Name="Barley", Vaccinated=true },
                            new Pet { Name="Boots", Vaccinated=false },
                            new Pet { Name="Whiskers", Vaccinated=false } };

         try
         {
            int numberUnvaccinated = pets.Count(p => p.Vaccinated == false);
            outputBlock.Text += String.Format("There are {0} unvaccinated animals.", numberUnvaccinated) + "\n";
         }
         catch (OverflowException)
         {
            outputBlock.Text += "The count is too large to store as an Int32." + "\n";
            outputBlock.Text += "Try using the LongCount() method instead." + "\n";
         }
      }

      // This code produces the following output:
      //
      // There are 2 unvaccinated animals.