Expand and Load: Fetching related entities in WCF Data Service

Objective

In this post, I will show you how to retrieve data from related entities in WCF Data Service.

If you are new to this topic, please read Introduction to WCF Data service and ODATA before going through below article

Let us say, we want to fetch details from related entities Customers and Order.

clip_image001

There are two ways to fetch data from both related entities.

1. Expand

2. LoadProperty

Using LoadProperty

Program.cs

  NorthwindEntities context = new NorthwindEntities(new Uri("http://localhost:61091/WcfDataService1.svc/"));
                try
                {
                    foreach (Order o in context.Orders)
                    {
                        context.LoadProperty(o, "Customer");
                        Console.WriteLine("Customer : {0}- Order Id: {1}", o.Customer.ContactName, o.OrderID);
                    }
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex.Message);
                }
                Console.Read();
            }

In above code clip_image003 So in above code load property is being used to load data from related entities. Output clip_image005 Using Expand Program.cs

 DataServiceQuery<Order> query =
                context.Orders.Expand("Order_Details,Customer");
            try
            {
                foreach (Order order in query.Take(4))
                {
                    Console.WriteLine("Customer: {0}", order.Customer.ContactName);
                    Console.WriteLine("Order ID: {0}", order.OrderID);
                    foreach (Order_Detail item in order.Order_Details)
                    {
                        Console.WriteLine("\tProduct: {0} - Quantity: {1}",
                            item.ProductID, item.Quantity);
                    }
                }
            }
            catch (DataServiceQueryException ex)
            {
                Console.WriteLine(ex.Message);
            }
            Console.Read();

So in above code

clip_image007

In above code Orders relation is expanded to Order_detail and Customer.

clip_image009

In above code retrieving top 4th record and iterating through the records to display.

Output

clip_image011

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WebException or Remote server name could not be resolved in WCF Data Service

Objective

This article will give a brief explanation on how to handle remote server name could not resolved exception in WCF Data Service

If you are new to this topic, please read Introduction to WCF Data service and ODATA before going through below article

Let us say, there is a WCF Data Service up and running on a particular server. We access that using below code at the client side

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Services.Client;
using ConsoleApplication1.ServiceReference1;
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            DataServiceContext context = new DataServiceContext(
                                         new Uri("http://localhost:61091/WcfDataService1.svc/"));
            DataServiceQuery<Employee> query = context.CreateQuery<Employee>("Employees");
                foreach (Employee e in query)
                {
                    Console.WriteLine(e.FirstName);
                }
            Console.Read();
        }
    }
}

And output is as below,

clip_image002

Every this is fine till this point. Now let us go ahead and modify the WCF Data Service URL to a false URL

clip_image004

And URL, I am giving is false one. Server abc does not exist. Now after modification code will look like

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Services.Client;
using ConsoleApplication1.ServiceReference1;
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            DataServiceContext context = new DataServiceContext(
                                         new Uri("http://abc:61091/WcfDataService1.svc/"));
            DataServiceQuery<Employee> query = context.CreateQuery<Employee>("Employees");
                foreach (Employee e in query)
                {
                    Console.WriteLine(e.FirstName);
                }
            Console.Read();
        }
    }
}

And when you try to run, you will get the run time exception as below,

clip_image005

Now to handle this exception put the foreach statement in try catch , so no modified code will look like

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Services.Client;
using ConsoleApplication1.ServiceReference1;
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            DataServiceContext context = new DataServiceContext(
                                         new Uri("http://abc:61091/WcfDataService1.svc/"));
            DataServiceQuery<Employee> query = context.CreateQuery<Employee>("Employees");
            try
            {
                foreach (Employee e in query)
                {
                    Console.WriteLine(e.FirstName);
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            Console.Read();
        }
    }
}

And now running output will be as below,

clip_image007

Step by Step walk Through on URL routing in ASP.Net 4.0

Objective

URL Routing is new feature in ASP.Net 4.0. This article will give a walkthrough on how to work with URL Routing and an introduction of that.

URL Routing

ASP.Net 4.0 URL Routing enables mapping between search engines optimized URL to physical web Form pages.

For example

http://localhost:36774/Products/All URL will be mapped to http://localhost:36774/AllProduct.aspx

Here the first URL is more search engine optimized. Using the routing engine ASP.Net 4.0 perform URL mapping.

Follow the below steps to see how to work with URL routing

Step 1

a. Open Visual studio

b. Create new project

c. Select ASP.Net Web Application from Web tab

d. Give any name of the project. I am giving RoutingDemo for purpose of this article.

clip_image002

Step 2

a. Right click on the project

b. Add a new folder

clip_image003

c. Give any name of your choice to the folder. I am giving name Model for purpose of this article

clip_image004

So after creating a new folder, you can see Model folder in solution explorer.

Step 3

a. Right click on Model folder and select Add new item

clip_image005

b. From Data tab select Linq to SQL classes . Give any name of your choice. I am giving name here NorthWindProduct for purpose of this article

clip_image007

c. Click on Server Explorer

clip_image008

d. From the Server Explorer , right click on Data Connections and select add connection

clip_image009

e. Below pop window will come.

clip_image010

Give data base server name at first. Select the authentication mode, you use to connect to your database and then select NorthWind data base. After giving these three fields click OK.

f. From Server explorer, expand the NorthWind database connection. From table tab select Product and drag it in design surface

clip_image011

g. After dragging on the design surface NorthWindProduct.dbml file as below

clip_image012

h. In solution explorer you can see inside Model folder three files. There is a NorthWindProductDataContext class inside RoutingDemo.Model name space , we will be using as data context

clip_image013

Step 4

We want to navigate to two different pages.

1. Select all Products (AllProduct.aspx) : This page will display all the Products

2. Select a particular product on basis of Product name. (ParticularProduct.aspx): This page will display product detail of given product name.

Step 4a

a. Right click on site.master in solution explorer. And add a content page

clip_image014

b. Now in solution explorer , you can notice you have WebForm.aspx

clip_image015

c. Right click on WebForm.aspx and rename this to AllProduct.aspx

clip_image016

After renaming the name, you will have AllProduct.aspx in solution explorer.

clip_image017

Step 4B

Follow the steps exactly the same as step 4A and add one more web form. Give name of this form as ParticularProduct.aspx instead of AllProduct.aspx. So now in solution explorer you can see two web forms has been added.

clip_image018

Step 4C

a. Open AllProduct.aspx

b. Drag GridView from Data tab of tool box and put it on AllProduct.aspx

clip_image019

So, in design AllPrduct.aspx will look as below,

clip_image021

AllProduct.aspx will look like below,

    <%@ Page Title="" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true" 
        CodeBehind="AllProduct.aspx.cs" Inherits="RoutingDemo.WebForm1" %>

    <asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" runat="server">

    </asp:Content>

   <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

   <asp:GridView ID="GridView1" runat="server"> 
   </asp:GridView>

  </asp:Content>

Now we need to write code to fetch data from LINQ to SQL class

AllProduct.aspx.cs

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Web;
    using System.Web.UI;
    using System.Web.UI.WebControls;
    using RoutingDemo.Model;
    namespace RoutingDemo
    {
        public partial class WebForm1 : System.Web.UI.Page
        {
            protected void Page_Load(object sender, EventArgs e)
            {
                GridView1.DataSource = Products;
                GridView1.DataBind();
            }
            private List<Product> _Product= null ;
            protected List<Product> Products
            {
                get
                {
                    if (_Product == null)
                    {
                        NorthWindProduct_DataContext context = new NorthWindProduct_DataContext();
                        return context.Products.ToList();
                    }
                    return _Product;
                }
            }
        }
    }

Explanation of Code

1. Put the namespace

clip_image022

2. Crated a protected property. In getter, I am checking for data member. If it is null, then I am creating instance of NorthWindProduct and fetching all the products.

clip_image024

3. On page load putting the property as data source of grid view.

clip_image025

Step 4D

a. Open ParticularProduct.aspx

b. Drag GridView from Data tab of tool box and put it on ParticularProduct.aspx

clip_image019[1]

So, in design ParticularProduct.aspx will look as below,

clip_image026

ParticularProduct.aspx will look like below,

   <%@ Page Title="" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true"  
CodeBehind="ParticularProduct.aspx.cs" Inherits="RoutingDemo.WebForm2" %>

   <asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" runat="server">

    </asp:Content>

    <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

    <asp:GridView ID="GridView1" runat="server">

   </asp:GridView>

   </asp:Content>

Now we need to write code to fetch data from LINQ to SQL class

ParticularProduct.aspx.cs


using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using RoutingDemo.Model;
namespace RoutingDemo
{
    public partial class WebForm2 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            GridView1.DataSource = new Model.Product[] { Products };
            GridView1.DataBind();
        }
        private Product _Product = null;
        protected Product Products
        {
            get
            {
                if (_Product == null)
                {
                    string prdName = Page.RouteData.Values["Name"] as string;
                    NorthWindProduct_DataContext context = new NorthWindProduct_DataContext();
                    return context.Products.Where(prd => prd.ProductName.Equals(prdName)).SingleOrDefault();
                }
                return _Product;
            }
        }
    }
}

Explanation of Code

1. Put the namespace

clip_image022[1]

2. Crated a protected property. In getter, I am checking for data member. If it is null, then I am creating instance of NorthWindProduct and fetching product with the given name

clip_image028

Here Name is the parameter name in the Route URL.

Step 5

Now open Global.asax

clip_image030

When you click on Global.ascx.cs . You will get below default code

clip_image031

Now we need to add

1. Name space

clip_image032

2. Method

clip_image034

In first mapPageRoute

All Product -> name of the rule in Global.ascx

Products/All -> Routing URL

~/AllProduct.aspx -> Name of the physical aspx file.

In second mapPageRoute

Selected Product -> name of the rule in Global.ascx

Products/Selected/ {name} -> Routing URL where name is the parameter

~/ParticularProduct.aspx -> name of the physical file

3. Call the above created method in application start

clip_image035

Global.ascx.cs

Step 6

Step 6a

Now open default.aspx

1. Drag two buttons from tool box and put on the page

2. Drag a text box and put on the page

3. Attach button click handler for both the button

Default.aspx

    <%@ Page Title="Home Page" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true"

    CodeBehind="Default.aspx.cs" Inherits="RoutingDemo._Default" %>

   <asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">
    </asp:Content>

   

   <asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">

  

   <h2>

  

  Welcome to ASP.NET 4.0 Routing Feature

  

  </h2>

  

  <asp:Button ID="btnAllProducts" runat="server" Text="All Products"

  

  Width="129px" onclick="btnAllProducts_Click" /><br />

  

   <asp:Button ID="btnSelectedProduct" runat="server" Text="Select Product"

  

   onclick="btnSelectedProduct_Click" />

  

   <asp:TextBox ID="txtSearch" runat="server" Width="167px"></asp:TextBox>

  

   </asp:Content>

  

Step 6b

On click event of btnAllProducts

clip_image037

There is no input parameter.

On click event of btnSelectedProduct

clip_image039

Here input parameter to navigate is in txtSearch text box.

Default.aspx.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace RoutingDemo
{
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
           // txtSearch.Text = "";
        }
        protected void btnAllProducts_Click(object sender, EventArgs e)
        {
            Response.RedirectToRoute("All Product");
        }
        protected void btnSelectedProduct_Click(object sender, EventArgs e)
        {
            Response.RedirectToRoute("Selected Product", new { name = txtSearch.Text });
        }
    }
}


Run the application

clip_image041

If you notice the above output and URL in address bar, it is

http://localhost:36774/Default.aspx

Now on clicking of All Products

clip_image043

Now if you see the URL in address bar

http://localhost:36774/Products/All

And this URL is search engine optimized URL.

In the same way when you click on Select Product button it will navigate to

http://localhost:36774/Products/Selected/Chai

Chai is the product name.

Conclusion

In this article, we saw what Routing mapping feature of ASP.Net 4.0. I hope this article was useful. Thanks for reading. Happy coding.