Tag: .NET

System.Lazy

Lazy loading isn't a new concept, it's a pattern that been around for a while to improve the performance of your apps by only loading objects when they are going to be used. For example if you have an object that contains a property of a list of customers then you only really need to populate it when you access the property not when the object was initially created, as it may never be used. At the same time though you don't want to be going off to the database every time access the property. So the simple solution is to have another private variable that stores if the customers property is populated or not and then check that in the property's get to determine if the data needs to be loaded or not.

Well now in .NET 4, lazy loading has been built into the framework with System.Lazy. Instead of the above all you need to do now is write something like this...

Lazy<Customers> _customers = new Lazy<Customers>();

What this will do is create you a customers object but only run the constructor when you actually access the objects Value property which will be of type Customers. e.g.

_customers.Value.CustomerData

It's that simple, but can get even better. The constructor may not be the only thing you want to run when you access the property the first time. In this case you would write something like...

_customers = new Lazy<Customers>(() =>
        {
            // Write any other initialization stuff in here
            return new Customers();
        });

I must point out though while as great as this is, it does have some limitations so you probably won't want to use it in all scenarios.

For more information check out the Lazy initialization page on MSDN

Introduction to Real Time Search

The Real Time Search this article relates to is a dll that comes included in the Web Client Software Factory one of Microsoft's patterns and practices downloads. What it can do and what this example will demonstrate is adding the ability cause a post back that will refresh an update panel as the users types into a search box. This can give a great effect and make a web app really user friendly in scenarios like searching photo's, emails or any general list.

First late me state though that this is in no way the most optimal way program. In most scenarios you could built a better result using something like JSON as their will be a lot less data transfer, which is also a general reason to avoid update panels. However this is also very quick and very easy to implement, not to mention if you've ever used update panels before you already know 90% of what's needed. This can also only work in situations where you have a good search that is going to return the result quickly, rather than leaving the user sitting there trying to work out why nothing's happening and where the search button has gone.

Implementing Real Time Search

For this example I will be filtering a table from a DB based on the search criteria and refreshing a Grid View with the results. I will be using a normal C# Web Site project with the Adventure Works sample DB from Microsoft. DB connection will be done using LINQ to EntityFramework, however there is no need to use this it is just my preference for the example.

First off set up you're website and db and make sure both are working with no problems. As results will be displayed in an Update Panel, get one of these along with a script manager added to your page, so it looks something like this:

1<form id="form1" runat="server">
2<div>
3<asp:ScriptManager ID="ScriptManager1" runat="server">
4</asp:ScriptManager>
5<asp:UpdatePanel ID="UpdatePanel1" runat="server">
6<ContentTemplate></ContentTemplate>
7</asp:UpdatePanel>
8</div>
9</form>

Next let's get the search working in the normal method, so I'm going to create my Entity Model and add a textbox and gridview to show the results. Again you can connect and show your results however you want. You should now have something like this in your aspx file:

1<form id="form1" runat="server">
2<div>
3<asp:ScriptManager ID="ScriptManager1" runat="server">
4</asp:ScriptManager>
5

6<asp:TextBox ID="txtSearch" runat="server" OnTextChanged="TextChanged" Text=""></asp:TextBox>
7

8<asp:UpdatePanel ID="UpdatePanel1" runat="server">
9<ContentTemplate>
10

11<asp:LinqDataSource ID="LinqDataSource1" runat="server" onselecting="LinqDataSource1_Selecting">
12</asp:LinqDataSource>
13

14<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataSourceID="LinqDataSource1">
15<Columns>
16<asp:BoundField DataField="ProductID" HeaderText="ProductID"
17ReadOnly="True" SortExpression="ProductID" />
18<asp:BoundField DataField="Name" HeaderText="Name"
19ReadOnly="True" SortExpression="Name" />
20<asp:BoundField DataField="ProductNumber" HeaderText="ProductNumber" ReadOnly="True" SortExpression="ProductNumber" />
21<asp:BoundField DataField="Color" HeaderText="Color"
22ReadOnly="True" SortExpression="Color" />
23<asp:BoundField DataField="SafetyStockLevel" HeaderText="SafetyStockLevel"
24ReadOnly="True" SortExpression="SafetyStockLevel" />
25<asp:BoundField DataField="ReorderPoint" HeaderText="ReorderPoint"
26ReadOnly="True" SortExpression="ReorderPoint" />
27</Columns>
28</asp:GridView>
29</ContentTemplate>
30

31</asp:UpdatePanel>
32</div>
33</form>

And this in your code behind:

1protected void LinqDataSource1_Selecting(object sender, LinqDataSourceSelectEventArgs e)
2{
3Model.AdventureWorks2008Entities AdventureWorkds = new Model.AdventureWorks2008Entities();
4var products = from p in AdventureWorkds.Product
5where p.Name.Contains(txtSearch.Text)
6select p;
7e.Result = products;
8}

Next its time to add the Real Time Search. Make sure you have the dll downloaded (you may need to compile the download to get it) and add it to your bin folder. Add the following to your page in the relevant places:

1<%@ Register Assembly="RealTimeSearch" Namespace="RealTimeSearch" TagPrefix="cc1" %>
2

3<cc1:RealTimeSearchMonitor ID="RealTimeSearchMonitor1" runat="server" AssociatedUpdatePanelID="UpdatePanel1">
4<ControlsToMonitor>
5<cc1:ControlMonitorParameter EventName="TextChanged" TargetID="txtSearch" />
6</ControlsToMonitor>
7</cc1:RealTimeSearchMonitor>

Important things to notice here are the AssociatedUpdatePanelId which tells the control what it has to refresh and the controls to monitor section which sets what the control to watch is called and the event name that will be fired when the post back is created. You will now need to corresponding control in your code behind like so:

1protected void TextChanged(object sender, EventArgs e)
2{
3GridView1.DataBind();
4}

Run the site and  you should find that the grid view now updates as you type (all be it with a slight delay).

To improve you can add other controls like update progress to show something happening which will help with any delays in displaying the results.

Visual Studio 2010 – Snippet Support

This week I have been playing around with the Beta 1 of Visual Studio 2010 and one thing I have to say I like is the new Snippet Support. We're all used to using it's InteliSense support allowing us to only type <aso:Bu and then hit space if we wanted to add a .NET button control to the page, but Snippets takes that a step further. Have a look at this example of adding a MultiView control to the page.

Adding A MultiView Control

The normal method would be to type <asp:Multi and then hit space to complete the word, followed by adding an ID, runat etc. All of which would be made easier with the current InteliSense support. Now though you can just type <mu and the Multiview snippet will be highlighted.

Hit tab and the word will be completed as below.

Hit tab again though and all the other stuff you were about to type is entered for you.

An auto ID is given, the runat and activeviewindex properties are also written for you along with the first view automatically added.

Snippet support isn't just limited to .NET controls either, it will also work with HTML markup and JavaScript.

HTML Example

In this HTML example of an "A" tag you can see as simple as an "A" tag may be, snippets can save you time even here by automatically writing the whole thing, and then recognising that you will want to change the values of the two sections and thus makes that even easier by then letting you tab between the two sections.

So there you have it, we can now all wonder how we ever survived having to write the first couple of letters of each word, when really all we ever needed to do was write the first couple of letters of the main tag and have the rest written for us.