MVVM Light Telling the View to play Storyboards

Sometimes you want to tell the view to play an animation (Storyboard). One simple way to do this is to define a StartStoryboardMessage class, populate this with the name of a Storyboard to play, then send it to the Messenger.

public class StartStoryboardMessage
{
    public string StoryboardName { getset; }
    public bool LoopForever { getset; }
}

In the viewmodel when you want to tell the view to play an animation:

Messenger.Default.Send(new StartStoryboardMessage { StoryboardName = "TimerFinAnimation",LoopForever=true });

The view (i.e. in the code-behind) registers for these messages:

Messenger.Default.Register<StartStoryboardMessage>(this, x => StartStoryboard(x.StoryboardName, x.LoopForever));

...

private void StartStoryboard(string storyboardName, bool loopForever)
{
    var storyboard = FindName(storyboardName) as Storyboard;
    if (storyboard != null)
    {
        if (loopForever) 
            storyboard.RepeatBehavior = RepeatBehavior.Forever;
        else
            storyboard.RepeatBehavior = new RepeatBehavior(1);
        storyboard.Begin();
    }
}

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MVVM Light Messenger Action Executing Multiple Times

With MVVM Light you can get into a situation where you code-behind's message handler gets called multiple times.

If the ctor for the view is registering for a message then the every time the view loads another subscription will be added; then when the message is sent the are effectively 2 'listeners' which end up executing the registered Action method multiple times.

One solution to this is to make sure you un-register when the view unloads.

The example below shows the code-behind for a simple settings page that registers for a DialogMessage in the ctor, and un-registers when the page is done with.

    public partial class Settings : PhoneApplicationPage
    {
        public Settings()
        {
            InitializeComponent();
            Messenger.Default.Register<DialogMessage>(this, DialogMessageHandler);
        }
        private void DialogMessageHandler(DialogMessage message)
        {
            var result = MessageBox.Show(message.Content, message.Caption, message.Button);
            
            message.ProcessCallback(result);
        }
        private void PhoneApplicationPage_Unloaded(object sender, RoutedEventArgs e)
        {
            Messenger.Default.Unregister(this);
        }
    }

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Cleaner Code in Unit Tests

One thing that can quickly become messy when writing unit tests is the creation of test objects. If the test object is a simple int, string, etc then it's not as much of a problem as when you a list or object graph you need to create.

Even using object initializers you can end up taking a lot of lines of indented code, and gets in the way of the tests.

One solution is to use a 'builder' class which will construct the object for you.

For example, rather than lots of initializer code you could write:

            _sampleData = new HistoryBuilder()
                .WithTimer(false11new DateTime(200011))
                .WithTimer(false11new DateTime(200011))
                .WithTimer(true11new DateTime(200011))
                .Build()

 You can multiple overloads of WithTimer (for example one which create adds a default Timer).

 Implementation of HistoryBuilder:

    public class HistoryBuilder
    {
        private readonly History _history;
        public HistoryBuilder()
        {
            _history = new History();
        }
        public HistoryBuilder WithTimer()
        {
            _history.Timers.Add(new Timer());
            return this;
        }
        public HistoryBuilder WithTimer(bool completed, int internalInteruptions, int externalInteruptions,
                                        DateTime time)
        {
            _history.Timers.Add(new Timer
                                    {
                                        Completed = completed,
                                        InternalInteruptionsCount = internalInteruptions,
                                        ExternalInteruptionsCount = externalInteruptions,
                                        StartedTime = time
                                    });
            return this;
        }
        public History Build()
        {
            return _history;
        }
    }

If you want to fill in the gaps in your C# knowledge be sure to check out my C# Tips and Traps training course from Pluralsight – get started with a free trial.

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MVVM Light Messenger Events Firing Multiple Times

If you register for a message in the ctor of your views code-behind, eg:

Messenger.Default.Register<DialogMessage>(this, DialogMessageHandler);

Every time you reload the view, i.e by navigating to it, the callback method (in this example DialogMessageHandler) can get called multiple times from the previous times ctor ran.

To fix this all you need to do create an event handler for the PhoneApplicationPage Unloaded and unregister the message (you can unregister more specifically using one of the other overloads):

Messenger.Default.Unregister(this);

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Introducing FeatureToggle

You can now take a first glance at my new open source project FeatureToggle

It's early days yet and I'm not quite what direction it will take.

The next thing I'd like to upload are some sample projects in WPF, WP7, ASP, etc so as to illustrate how to use FeatureToggle but also to help drive the design from the point of the consumer.

More info of the idea of feature toggle can be found at Martin Fowler's site.

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Comparing 2 Locations in Windows Phone 7

If you are using Microsoft.Phone.Controls.Maps.Platform.Location in your WP7 application and you want to see if 2 Locations refer to the same place (i.e. the same altitude, latitude and longitude are all equal) then using Location.Equals or == will not work.

This is because Location inherits from Object and doesn't override Equals method, which results in a simple reference equality check.

The extension method below can be used instead:

using Microsoft.Phone.Controls.Maps.Platform;
namespace DontCodeTired
{
    public static class LocationExtensionMethods
    {
        public static bool IsSamePlaceAs(this Location me, Location them)
        {
            return me.Latitude == them.Latitude &&
                   me.Longitude == them.Longitude &&
                   me.Altitude == them.Altitude;
        }
    }
}

 

Example usage:

    [TestFixture]
    public class LocationExtensionMethodsTest
    {
        [Test]
        public void ShouldRecogniseWhenTwoLocationsReferToTheSamePlace()
        {
            var l1 = new Location {Latitude = double.MinValue, Longitude = double.MaxValue};
            var l2 = new Location { Latitude = double.MinValue, Longitude = double.MaxValue };
            Assert.IsTrue(l1.IsSamePlaceAs(l2));
        }
        [Test]
        public void ShouldRecogniseWhenTwoLocationsReferToDifferentPlacess()
        {
            var l1 = new Location { Latitude = double.MinValue - double.MinValue, Longitude = double.MaxValue };
            var l2 = new Location { Latitude = double.MinValue, Longitude = double.MaxValue };
            Assert.IsFalse(l1.IsSamePlaceAs(l2));
        }
    }

 

 

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Improved GridView & ListView Row Selection in ASP.NET 4.0

Previous versions of GridView and ListView selection behaviour operating in a potentially confusing way to the user. For example, if the third row was selected and then page 2 was selected, the third row on page 2 would also be selected. ASP.NET 4 fixes this by adding the EnablePersistedSelection and DataKeyNames properties to provide what MSDN calls "Persisted Selection".

To make selection work more as expected simple set EnablePersistedSelection="True" on the GridView or ListView and set the DataKeyNames property to the unique\primary key\property of the underlying databound object\row\etc.

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Controlling HTML IDs in ASP.NET 4.0 Webforms

ASP.NET 4 introduces more control over how client-side IDs are rendered by ASP.NET controls. By default ASP.NET 4 will render client IDs in the same way as ASP.NET 3.5 and earlier.

To change the way IDs are generated, the ClientIDMode property can be set - this can either be done on individual controls or at the page level in the @Page directive.

The default ClientIDMode value for controls is Inherit and the default for the Page is AutoID - if we change ClientIDMode at the Page level, the controls on that page will inherit the setting.

The options for ClientIDMode are:

  • AutoID: (Page default) generates IDs the same way as prior versions. Use for backward compatibility or when you don't care about what IDs are generated.
  • Inherit: (Control default): uses the value from the parent container.
  • Static: always sets the client-side ID to the same as the server-side ID property. Use to guarantee the client-side ID of a control - may result in duplicate IDs on the client which may cause problems if you have JavaScript looking for the control by ID.
  • Predictable: Can be used for content inside a databound GridView or ListView to append the unique id/key of the bound object (e.g. the primary key of a databound database record).

The following snippets of HTML output shows how the different settings change client-side IDs when a Label control called "NumberInStockLabel" is used inside a databound ListView.

AutoID, No ClientIDRowSuffix Specified

<td><span id="AutoIDListView_ctrl0_NumberInStockLabel">22</span></td>

Predictable, ClientIDRowSuffix=ProductID

<td><span id="PredictableListView_NumberInStockLabel_44">22</span></td>

The 44 at the end of the ID is the ProductID property from the underlying databound item.

Predictable, No ClientIDRowSuffix Specified

<td><span id="PredictableListViewNoClientIDRowSuffix_NumberInStockLabel_0">22</span></td>

The 0 at the end of the ID is a simple sequential number generated by ASP.NET, this is because we have not specified a value for ClientIDRowSuffix; subsequent rows would end _1 _2 _3 etc.

Static, No ClientIDRowSuffixSpecified

<td><span id="NumberInStockLabel">22</span></td>

The id is exactly the same as the one we set in markup; subsequent rows would all have exactly the same id.

Complete Source Markup

<%@ Page Language="C#" AutoEventWireup="true"
CodeBehind="Products.aspx.cs"
Inherits="clientIDs.Products"
ViewStateMode="Disabled" %>

<!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 runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>


        <asp:ObjectDataSource ID="odsProducts" runat="server"
            SelectMethod="GetProducts"
            TypeName="clientIDs.MockProductDB" />


        <h3>ListView, AutoID, No ClientIDRowSuffix</h3>
        <table>
            <tr>
                <th>Product ID</th>
                <th>Description</th>
                <th>Stock</th>
            </tr>
            <asp:ListView ID="AutoIDListView" runat="server"
                DataSourceID="odsProducts"
                ClientIDMode="AutoID"
                ClientIDRowSuffix="ProductID">
                <ItemTemplate>
                    <tr>
                        <td><%# Eval("ProductID") %></td>
                        <td><%# Eval("Description")%></td>
                        <td><asp:Label ID="NumberInStockLabel" runat="server" Text='<%# Eval("NumberInStock") %>' /></td>
                    </tr>
                </ItemTemplate>
            </asp:ListView>
        </table>



        <h3>ListView, Predictable, ClientIDRowSuffix=ProductID</h3>
        <table>
            <tr>
                <th>Product ID</th>
                <th>Description</th>
                <th>Stock</th>
            </tr>
            <asp:ListView ID="PredictableListView" runat="server"
                DataSourceID="odsProducts"
                ClientIDMode="Predictable"
                ClientIDRowSuffix="ProductID">
                <ItemTemplate>
                    <tr>
                        <td><%# Eval("ProductID") %></td>
                        <td><%# Eval("Description")%></td>
                        <td><asp:Label ID="NumberInStockLabel" runat="server" Text='<%# Eval("NumberInStock") %>' /></td>
                    </tr>
                </ItemTemplate>
            </asp:ListView>
        </table>



         <h3>ListView, Predictable, No ClientIDRowSuffix set</h3>
        <table>
            <tr>
                <th>Product ID</th>
                <th>Description</th>
                <th>Stock</th>
            </tr>
            <asp:ListView ID="PredictableListViewNoClientIDRowSuffix" runat="server"
                DataSourceID="odsProducts"
                ClientIDMode="Predictable">
                <ItemTemplate>
                    <tr>
                        <td><%# Eval("ProductID") %></td>
                        <td><%# Eval("Description")%></td>
                        <td><asp:Label ID="NumberInStockLabel" runat="server" Text='<%# Eval("NumberInStock") %>' /></td>
                    </tr>
                </ItemTemplate>
            </asp:ListView>
        </table>





        <h3>ListView, Static, No ClientIDRowSuffix set</h3>
        <table>
            <tr>
                <th>Product ID</th>
                <th>Description</th>
                <th>Stock</th>
            </tr>
            <asp:ListView ID="StaticListView" runat="server"
                DataSourceID="odsProducts"
                ClientIDMode="Static">
                <ItemTemplate>
                    <tr>
                        <td><%# Eval("ProductID") %></td>
                        <td><%# Eval("Description")%></td>
                        <td><asp:Label ID="NumberInStockLabel" runat="server" Text='<%# Eval("NumberInStock") %>' /></td>
                    </tr>
                </ItemTemplate>
            </asp:ListView>
        </table>



    </div>
    </form>
</body>
</html>

 

Complete HTML Output

 
 
<!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><title>
 
</title></head>
<body>
    <form method="post" action="Products.aspx" id="form1">
<div class="aspNetHidden">
<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwUKLTkwMjEwMjAxN2QYBAUOU3RhdGljTGlzdFZpZXcPFCsADmRkZGRkZGQ8KwAEAAIEZGRkZgL/////D2QFJlByZWRpY3RhYmxlTGlzdFZpZXdOb0NsaWVudElEUm93U3VmZml4DxQrAA5kZGRkZGRkPCsABAACBGRkZGYC/////w9kBRNQcmVkaWN0YWJsZUxpc3RWaWV3DxQrAA5kZGRkZGRkPCsABAACBGQVAQlQcm9kdWN0SUQUKwAEFCsAAQIsFCsAAQIDFCsAAQLIIhQrAAECYGYC/////w9kBQ5BdXRvSURMaXN0Vmlldw8UKwAOZGRkZGRkZDwrAAQAAgRkFQEJUHJvZHVjdElEFCsABBQrAAECLBQrAAECAxQrAAECyCIUKwABAmBmAv////8PZBoTurOO0ZN1r5PaB5cscPKdDFEGlp47JvHGSM55AYQ9" />
</div>
 
    <div>
       
 
 
 
 
        <h3>ListView, AutoID, No ClientIDRowSuffix</h3>
        <table>
            <tr>
                <th>Product ID</th>
                <th>Description</th>
                <th>Stock</th>
            </tr>
           
                    <tr>
                        <td>44</td>
                        <td>product 1</td>
                        <td><span id="AutoIDListView_ctrl0_NumberInStockLabel">22</span></td>
                    </tr>
               
                    <tr>
                        <td>3</td>
                        <td>product 2</td>
                        <td><span id="AutoIDListView_ctrl1_NumberInStockLabel">11</span></td>
                    </tr>
               
                    <tr>
                        <td>4424</td>
                        <td>product 3</td>
                        <td><span id="AutoIDListView_ctrl2_NumberInStockLabel">1</span></td>
                    </tr>
               
                    <tr>
                        <td>96</td>
                        <td>product 4</td>
                        <td><span id="AutoIDListView_ctrl3_NumberInStockLabel">0</span></td>
                    </tr>
               
        </table>
 
 
 
        <h3>ListView, Predictable, ClientIDRowSuffix=ProductID</h3>
        <table>
            <tr>
                <th>Product ID</th>
                <th>Description</th>
                <th>Stock</th>
            </tr>
           
                    <tr>
                        <td>44</td>
                        <td>product 1</td>
                        <td><span id="PredictableListView_NumberInStockLabel_44">22</span></td>
                    </tr>
               
                    <tr>
                        <td>3</td>
                        <td>product 2</td>
                        <td><span id="PredictableListView_NumberInStockLabel_3">11</span></td>
                    </tr>
               
                    <tr>
                        <td>4424</td>
                        <td>product 3</td>
                        <td><span id="PredictableListView_NumberInStockLabel_4424">1</span></td>
                    </tr>
               
                    <tr>
                        <td>96</td>
                        <td>product 4</td>
                        <td><span id="PredictableListView_NumberInStockLabel_96">0</span></td>
                    </tr>
               
        </table>
 
 
 
         <h3>ListView, Predictable, No ClientIDRowSuffix set</h3>
        <table>
            <tr>
                <th>Product ID</th>
                <th>Description</th>
                <th>Stock</th>
            </tr>
           
                    <tr>
                        <td>44</td>
                        <td>product 1</td>
                        <td><span id="PredictableListViewNoClientIDRowSuffix_NumberInStockLabel_0">22</span></td>
                    </tr>
               
                    <tr>
                        <td>3</td>
                        <td>product 2</td>
                        <td><span id="PredictableListViewNoClientIDRowSuffix_NumberInStockLabel_1">11</span></td>
                    </tr>
               
                    <tr>
                        <td>4424</td>
                        <td>product 3</td>
                        <td><span id="PredictableListViewNoClientIDRowSuffix_NumberInStockLabel_2">1</span></td>
                    </tr>
               
                    <tr>
                        <td>96</td>
                        <td>product 4</td>
                        <td><span id="PredictableListViewNoClientIDRowSuffix_NumberInStockLabel_3">0</span></td>
                    </tr>
               
        </table>
 
 
 
 
 
        <h3>ListView, Static, No ClientIDRowSuffix set</h3>
        <table>
            <tr>
                <th>Product ID</th>
                <th>Description</th>
                <th>Stock</th>
            </tr>
           
                    <tr>
                        <td>44</td>
                        <td>product 1</td>
                        <td><span id="NumberInStockLabel">22</span></td>
                    </tr>
               
                    <tr>
                        <td>3</td>
                        <td>product 2</td>
                        <td><span id="NumberInStockLabel">11</span></td>
                    </tr>
               
                    <tr>
                        <td>4424</td>
                        <td>product 3</td>
                        <td><span id="NumberInStockLabel">1</span></td>
                    </tr>
               
                    <tr>
                        <td>96</td>
                        <td>product 4</td>
                        <td><span id="NumberInStockLabel">0</span></td>
                    </tr>
               
        </table>
 
 
 
    </div>
    </form>
</body>
</html>

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URL Routing in ASP.Net 4 Web Forms

ASP.Net 4 simplifies the routing experience introduced in ASP.NET 3.5 SP1. Routing allows the use of more meaningful or 'friendly' URLs (which may also benefit search engine ranking).

For example, rather than .../ShowCountryDetails.aspx?country=australia routing could be enabled so the url looked like .../countries/australia

Defining Routes

You can define routes using the MapPageRoute method of the RouteCollection class. The code below is an extract from Global.asax.cs, the method RegisterRoutes is called from application start, and it's here that a route is registered:

protected void Application_Start(object sender, EventArgs e)
{
    RegisterRoutes(RouteTable.Routes);
}



void RegisterRoutes(RouteCollection routes)
{
    /*  Create a routing which maps SayHello to ShowGreeting.aspx
        and defines 2 parameters, greeting and name. */
    routes.MapPageRoute("ShowGreetingRoute",
        "SayHello/{greeting}/{name}",
        "~/ShowGreeting.aspx");
}
 

Accessing URL Param Values In Markup

When routing is in use, RouteValue expressions can be used in markup:

<asp:Literal Text="<%$RouteValue:greeting%>" runat="server" />

Accessing URL Param Values In Code

In code we can use Page.RouteData to get the values of any routed URL parameter values; we can either check for a null before calling ToString() or as in the following example use ContainsKey to check first (in practice you wouldn't use 'magic' string literals for "greeting", rather you'd define these as constants, etc.):

string greetingText = "no greeting text specified";
       
if (Page.RouteData.Values.ContainsKey("greeting"))
        greetingText = Page.RouteData.Values["greeting"].ToString();

Creating Routed URLs in Markup

We can create routed URLs in markup by using RouteUrl expressions:

<asp:HyperLink ID="declarativeLinkToRoutedPage"
    NavigateUrl="<%$RouteUrl:greeting=bonjour, name=Bob, routename=ShowGreetingRoute%>"
    Text="Say hello to Bob in French" runat="server" />

Creating Routed URLs in Code

Instead of setting NavigateUrl using RouteUrl in markup, we could set it in code RouteValueDictionary & VirtualPathData:

/// <summary>
/// Example of setting a Hyperlink's NavigateUrl in code
/// </summary>
private void SetHyperlinkNavigateUrlProperty()
{
    RouteValueDictionary routeParamValues = new RouteValueDictionary
    {
        {"greeting", "goodnight"},
        {"name", "Fred"}
    };

    VirtualPathData vpd = RouteTable.Routes.GetVirtualPath(null, routeParamValues);

    linkSetInCodeToRoutedPage.NavigateUrl = vpd.VirtualPath;
}

Using Routed Values as Parameters in Bound Data Sources

We can define RouteParameter in a data source that is being bound to.

The following markup shows a DetailsView being bound to an ObjectDataSource. The SelectParameters collection defines a RouteParameter which will pass the value of the 'name' URL routed parameter to the GetPersonsAge method of the MockDataBase class.

<asp:ObjectDataSource ID="odsPersonsAge" runat="server"
    SelectMethod="GetPersonsAge" TypeName="ASPNET4Routing.MockDataBase">
    <SelectParameters>
        <asp:RouteParameter Name="name" RouteKey="name" Type="String" />
    </SelectParameters>
</asp:ObjectDataSource>
      
<asp:DetailsView ID="DetailsView1" runat="server" DataSourceID="odsPersonsAge"
                AutoGenerateRows="true" /> 

<asp:ObjectDataSource ID="odsPersonsAge" runat="server"
    SelectMethod="GetPersonsAge" TypeName="ASPNET4Routing.MockDataBase">
    <SelectParameters>
        <asp:RouteParameter Name="name" RouteKey="name" Type="String" />
    </SelectParameters>
</asp:ObjectDataSource>

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