Simple LINQ Projection Example

Here is a simple example using LINQ projection. It takes a List<string> that include space-delimited strings, queries them and then project into an IEnumerable<Person>. I then loop through the output sequence and write the results to the console.

class Program
    {
        static void Main(string[] args)
        {
            List<string> people = new List<string>
                { "Joe Smith 20", "Jim Jackson 30", "Jason Suzuki 40" };
            IEnumerable<Person> query =
                from p in people
                select new Person
                {
                    FirstName = p.Split(' ')[0],
                    LastName = p.Split(' ')[1],
                    Age = Convert.ToInt32(p.Split(' ')[2])
                };
            foreach (Person p in query)
            {
                Console.WriteLine("First Name:\t{0}\r\nLastName:\t{1}\r\nAge:\t\t{2}",
                    p.FirstName, p.LastName, p.Age);
            }
        }
    }

    public class Person
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public int Age { get; set; }
    }

The Albahari Brothers Rock!

I recently ordered two books and wanted to give a quick plug to the Albahari brothers. They have provided a great service to C# programmers by writing two excellent books that cover an incredible amount of material with examples in a very few pages. Unlike many technical books these are thorough, concise, and believe it or not, portable! I have many other books that have far more pages and simply don't measure up in explaining or providing good examples. I should also mention that they have also written the new O'Reilly C# In A Nutshell book. I own the older version, but find it more of a reference book and am less likely to throw it in my backpack.

In addition, they have written a lightweight tool that allows you to learn and write ad-hoc LINQ expressions. You can even connect to a SQL Server and write SQL queries as well. What's more, they have included all of the code samples from their books. (See screenshot below)

	C# 3.0 Pocket Reference: Instant Help for C# 3.0 Programmers Authors: Joseph Albahari and Ben Albahari Publisher: O'Reilly Publish Date: 02/26/2008 Pages: 172 Current Amazon Price: $10.19 (Used - $7.79)
	LINQ Pocket Reference: The Concise Reference to LINQ via C# 3.0 Authors: Joseph Albahari and Ben Albahari Publisher: O'Reilly Publish Date: 02/26/2008 Pages: 242 Current Amazon Price: $10.19 (Used - $8.00)
	LINQPad Authors: Joseph Albahari and Ben Albahari Free Download!

GridView + DetailsView + LinqDataSource + ModalPopupExtender - Hello World Example

I recently found a limitation when using a GridView, DetailsView, LinqDataSource, and ModalPopupExtender that prevented any records other than the first to be displayed in the DetailsView shown in the ModalPopupExtender. Although I am told that this can be alleviated by using an UpdatePanel, I was working in an extranet environment using Juniper VPN which doesn't like UpdatePanels or at least rewrites the HTML in such a way that prevents an UpdatePanel from working properly. In order to get this to work, all you need to do is hook up the RowCommand and RowDataBound events of the GridView so that a CommandArgument is created and then subsequently used in a Linq query when the item is clicked. You will need SQLExpress with the Northwind sample database and a Linq to SQL Classes (dbml) file that point to the Products table to get this to work.

For amusement, you can read about my struggles in the ASP.NET Forum here: http://forums.asp.net/p/1224034/2195642.aspx Also, a special thanks from the tiredblogger with his post which got me on the right track. http://tiredblogger.wordpress.com/2007/09/16/using-a-modal-popup-to-modify-linq-gridviews/

Without further ado, the code:

ASPX

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Test.aspx.cs" Inherits="LinqTester.Test" EnableEventValidation="false" %>

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>Untitled Page</title>
    <style type="text/css">
        .modalBackground
        {
            background-color: Black;
            filter: alpha(opacity=80);
            opacity: 0.8;
        }
    </style>
</head>
<body>
    <form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager1" runat="server" />
    <div style="text-align: center;">
        <table>
            <tr>
                <td style="text-align: left;">
                    <asp:GridView ID="GridView1" runat="server" AllowPaging="True" DataKeyNames="ProductID"
                        AllowSorting="True" AutoGenerateColumns="False" DataSourceID="LinqDataSource1"
                        OnRowDataBound="GridView1_RowDataBound"
                        onrowcommand="GridView1_RowCommand">
                        <Columns>
                            <asp:BoundField DataField="ProductName" HeaderText="ProductName" ReadOnly="True"
                                SortExpression="ProductName" />
                            <asp:BoundField DataField="QuantityPerUnit" HeaderText="QuantityPerUnit" ReadOnly="True"
                                SortExpression="QuantityPerUnit" />
                            <asp:BoundField DataField="ProductID" HeaderText="ProductID" ReadOnly="True" SortExpression="ProductID" />
                            <asp:TemplateField>
                                <ItemTemplate>
                                    <asp:LinkButton ID="Details" runat="server" CommandName="ShowDetails" Text="Details"></asp:LinkButton>
                                </ItemTemplate>
                            </asp:TemplateField>
                        </Columns>
                    </asp:GridView>
                </td>
            </tr>
        </table>
    </div>
    <asp:Panel ID="UpdateRecordPanel" runat="server" CssClass="" Style="display:none">
        <asp:DetailsView ID="DetailsView1" runat="server" AutoGenerateRows="False" DataSourceID="LinqDataSource2"
            Height="50px" Width="125px" BackColor="White">
            <Fields>
                <asp:BoundField DataField="ProductName" HeaderText="ProductName" ReadOnly="True"
                    SortExpression="ProductName" />
                <asp:BoundField DataField="QuantityPerUnit" HeaderText="QuantityPerUnit" ReadOnly="True"
                    SortExpression="QuantityPerUnit" />
                <asp:BoundField DataField="UnitPrice" HeaderText="UnitPrice" ReadOnly="True" SortExpression="UnitPrice" />
                <asp:BoundField DataField="UnitsInStock" HeaderText="UnitsInStock" ReadOnly="True"
                    SortExpression="UnitsInStock" />
                <asp:BoundField DataField="UnitsOnOrder" HeaderText="UnitsOnOrder" ReadOnly="True"
                    SortExpression="UnitsOnOrder" />
                <asp:BoundField DataField="ReorderLevel" HeaderText="ReorderLevel" ReadOnly="True"
                    SortExpression="ReorderLevel" />
                <asp:CheckBoxField DataField="Discontinued" HeaderText="Discontinued" ReadOnly="True"
                    SortExpression="Discontinued" />
            </Fields>
        </asp:DetailsView>
        <asp:Button ID="CancelPopupButton" runat="server" Text="Cancel" />
    </asp:Panel>

    <cc1:ModalPopupExtender ID="ModalPopupExtender1" runat="server"
        BackgroundCssClass="modalBackground"
        CancelControlID="CancelPopupButton"
        PopupControlID="UpdateRecordPanel"
        TargetControlID="HiddenButton" >
    </cc1:ModalPopupExtender>

    <asp:Button ID="HiddenButton" runat="server" Style="display:none" />   

    <asp:LinqDataSource ID="LinqDataSource1" runat="server" ContextTypeName="LinqTester.Data.NorthwindDataContext"
        Select="new (ProductName, QuantityPerUnit, ProductID)" TableName="Products">
    </asp:LinqDataSource>
    <asp:LinqDataSource ID="LinqDataSource2" runat="server" ContextTypeName="LinqTester.Data.NorthwindDataContext"
        Select="new (ProductName, QuantityPerUnit, UnitPrice, UnitsInStock, UnitsOnOrder, ReorderLevel, Discontinued)"
        TableName="Products" Where="ProductID == @ProductID">
        <WhereParameters>
            <asp:ControlParameter ControlID="GridView1" Name="ProductID" PropertyName="SelectedValue"
                DefaultValue="1" Type="Int32" />
        </WhereParameters>
    </asp:LinqDataSource>
    </form>
</body>
</html>

ASPX.CS

using System;
using System.Collections;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using AjaxControlToolkit;

namespace LinqTester
{
    public partial class Test : System.Web.UI.Page
    {
        protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
        {
            if (e.Row.RowType != DataControlRowType.Header && e.Row.RowType != DataControlRowType.Footer && e.Row.RowType != DataControlRowType.Pager)
            {
                LinkButton lb = e.Row.FindControl("Details") as LinkButton;
                if (lb != null)
                {
                    lb.CommandArgument = ((TableCell)e.Row.Controls[2]).Text;
                }
            }
        }

        protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
        {
            if (e.CommandName == "ShowDetails")
            {
                ProductDetails productDetails = GetProductDetails(Convert.ToInt32(e.CommandArgument));
                DetailsView1.Rows[0].Cells[1].Text = productDetails.ProductName;
                DetailsView1.Rows[1].Cells[1].Text = productDetails.Quantity;
                DetailsView1.Rows[2].Cells[1].Text = productDetails.UnitPrice.ToString();
                DetailsView1.Rows[3].Cells[1].Text = productDetails.UnitsInStock.ToString();
                DetailsView1.Rows[4].Cells[1].Text = productDetails.UnitsOnOrder.ToString();
                DetailsView1.Rows[5].Cells[1].Text = productDetails.ReorderLevel.ToString();
                DetailsView1.Rows[6].Cells[1].Text = productDetails.Discontinued.ToString();
                ModalPopupExtender1.Show();
            }
        }

        private ProductDetails GetProductDetails(int productId)
        {
            LinqTester.Data.NorthwindDataContext northwind = new LinqTester.Data.NorthwindDataContext();
            List productDetails = (from p in northwind.Products
                                             where p.ProductID == productId
                                             select new ProductDetails
                                             {
                                                 ProductName = p.ProductName,
                                                 Quantity = p.QuantityPerUnit,
                                                 UnitPrice = p.UnitPrice.HasValue == true ? 0 : (int)p.UnitPrice,
                                                 UnitsInStock = p.UnitsInStock.HasValue == true ? 0 : (int)p.UnitsInStock,
                                                 UnitsOnOrder = p.UnitsOnOrder.HasValue == true ? 0 : (int)p.UnitsOnOrder,
                                                 ReorderLevel = p.ReorderLevel.HasValue == true ? 0 : (int)p.ReorderLevel,
                                                 Discontinued = p.Discontinued
                                             }).ToList();
            return productDetails[0];
        }      
    }

    public class ProductDetails
    {
        public string ProductName { get; set; }
        public string Quantity { get; set; }
        public decimal UnitPrice { get; set; }
        public int UnitsInStock { get; set; }
        public int UnitsOnOrder { get; set; }
        public int ReorderLevel { get; set; }
        public bool Discontinued { get; set; }
    }

}