Understanding Iterators, Part 2: Listing 2

The Visual Basic lambda iterator method.

Public Sub CategoryClickLambda(CategoryName As String)
    Dim iL As New IteratorsDemo.IteratorsLayer
    lstCoursesAndModules.Items.Clear()
    Dim courseCount = 0
    Dim moduleCount = 0

    Dim svcUri As Uri = New Uri("http://www.pluralsight-training.net/odata/")
    Dim provider = New PluralsightService.CourseProvider(svcUri)
    Dim CourseModulesLambda =
        Iterator Function() As IEnumerable(Of CourseWithModules)
            Dim courses = iL.GetCoursesForCategory(CategoryName)
            For Each course In courses
                Dim courseWithModules = New CourseWithModules _
                    With {.Course = course, .Modules = iL.GetModulesForCourse(course.Name)}
                Yield courseWithModules
            Next
        End Function

    For Each item In CourseModulesLambda()
        lstCoursesAndModules.Items.Add(String.Empty)
        Dim CourseLine = String.Format("    {0}  ({1})", item.Course.Title, item.Course.Name)
        lstCoursesAndModules.Items.Add(CourseLine)
        courseCount += 1

        For Each moduleItem In item.Modules
            Dim ModuleLine = String.Format("        {0}  ({1})", moduleItem.Title, moduleItem.VideoLength)
            lstCoursesAndModules.Items.Add(ModuleLine)
            moduleCount += 1
        Next
        Application.DoEvents()
    Next

    Dim header = String.Format("There are {0} Courses With {1} Modules For Category {2}", courseCount, moduleCount, CategoryName)
    lstCoursesAndModules.Items.Insert(0, header)
  End Sub

About the Author

Joe Kunk is a Microsoft MVP in Visual Basic, three-time president of the Greater Lansing User Group for .NET, and developer for Dart Container Corporation of Mason, Michigan. He's been developing software for over 30 years and has worked in the education, government, financial and manufacturing industries. Kunk's co-authored the book "Professional DevExpress ASP.NET Controls" (Wrox Programmer to Programmer, 2009). He can be reached via email at joekunk@gmail.com.