Thursday, 24 May 2012

C# Programming : Grouping data using a LINQ query In LINQ To Objects

You can also perform Grouping in LINQ to Objects using a LINQ Query.
This LINQ query uses the group keyword to group the Books data by pages.
Additionally, because a group action does not naturally result in any output, the query creates a custom query projection using the techniques discussed earlier.

Using LINQ to do this grouping enables you to significantly reduce the lines of code required.
This is also improve the readability and clarity of the code.

C# Example :
    public class Books
    {
        public string Title { get; set; }
        public string ISBN { get; set; }
        public DateTime ReleaseDate { get; set; }
        public int Pages { get; set; }
    }

    protected void Page_Load(object sender, EventArgs e)
    {
        var bookslist = GetBooksList();
        //var query = from bl in bookslist select bl;
        var query = from bl in bookslist
               group bl by bl.Pages into g
                    select new {Pages= g.Key,Count=g.Count() };
        this.gvBooks.DataSource = query;
        this.gvBooks.DataBind();
    }
    public List<Books> GetBooksList()
    {
        return new List<Books> {
                        new Books { Title="ASP.NET",ISBN="asp1",ReleaseDate= DateTime.Parse( "11/11/2010") ,Pages=200},
                        new Books { Title="C#.NET",ISBN="c#2",ReleaseDate= DateTime.Parse( "10/11/2010") ,Pages=500},
                        new Books { Title="VB.NET",ISBN="vb3",ReleaseDate= DateTime.Parse( "5/5/2009") ,Pages=400},
                        new Books { Title="SQL Server",ISBN="sql4",ReleaseDate= DateTime.Parse( "6/9/2010"),Pages=300 },
                        new Books { Title="JAVA",ISBN="java5",ReleaseDate= DateTime.Parse( "8/5/2011"),Pages=400 }
        
        };

    }

VB.net Example :
    Public Class Books
        Public Property Title() As String
        Public Property ISBN As String
        Public Property ReleaseDate As Date
        Public Property Pages As Integer
    End Class
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Dim bookslist = GetBooksList()
        'Dim query = From bl In bookslist _
        '            Select bl
        Dim query = From bl In bookslist _
                    Group By bl.Pages Into g = Group, Count()
        gvBooks.DataSource = query
        gvBooks.DataBind()
    End Sub
    Public Function GetBooksList() As List(Of Books)
        Dim lstBooks As New List(Of Books) From { _
                                New Books With {.Title = "ASP.NET", .ISBN = "asp1", .ReleaseDate = DateTime.Parse("11/11/2010"), .Pages = 200}, _
                                New Books With {.Title = "C#.NET", .ISBN = "c#2", .ReleaseDate = DateTime.Parse("10/11/2010"), .Pages = 500}, _
                                New Books With {.Title = "VB.NET", .ISBN = "vb3", .ReleaseDate = DateTime.Parse("5/5/2009"), .Pages = 400}, _
                                New Books With {.Title = "SQL Server", .ISBN = "sql4", .ReleaseDate = DateTime.Parse("6/9/2010"), .Pages = 300}, _
                                New Books With {.Title = "JAVA", .ISBN = "java5", .ReleaseDate = DateTime.Parse("8/5/2011"), .Pages = 400}}

        Return lstBooks
    End Function

4 comments:

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    ReplyDelete
    Replies
    1. Hi,
      Thanks for your valuable comments.

      Delete
  2. Replies
    1. Hi Marek,
      Thanks for your valuable comments.

      Delete