Type Equivalence Embedded Interop Types

16 April 2010 brianbruff

 

Beginning with the .NET Framework version 4, the common language runtime supports embedding type information for COM types directly into managed assemblies, instead of requiring the managed assemblies to obtain type information for COM types from interop assemblies. Because the embedded type information includes only the types and members that are actually used by a managed assembly, two managed assemblies might have very different views of the same COM type. Each managed assembly has a different Type object to represent its view of the COM type. The common language runtime supports type equivalence between these different views for interfaces, structures, enumerations, and delegates.

Type equivalence means that a COM object that is passed from one managed assembly to another can be cast to the appropriate managed type in the receiving assembly.

NoteNote

Type equivalence and embedded interop types simplify the deployment of applications and add-ins that use COM components, because it is not necessary to deploy interop assemblies with the applications. Developers of shared COM components still have to create primary interop assemblies (PIAs) if they want their components to be used by earlier versions of the .NET Framework.
Type Equivalence

Equivalence of COM types is supported for interfaces, structures, enumerations, and delegates. COM types qualify as equivalent if all of the following are true:

  • The types are both interfaces, or both structures, or both enumerations, or both delegates.

  • The types have the same identity, as described in the next section.

  • Both types are eligible for type equivalence, as described in the Marking COM Types for Type Equivalence section.

Type Identity

Two types are determined to have the same identity when their scopes and identities match, in other words, if they each have the TypeIdentifierAttribute attribute, and the two attributes have matching Scope and Identifier properties. The comparison for Scope is case-insensitive.

If a type does not have the TypeIdentifierAttribute attribute, or if it has a TypeIdentifierAttribute attribute that does not specify scope and identifier, the type can still be considered for equivalence as follows:

Marking COM Types for Type Equivalence

You can mark a type as eligible for type equivalence in two ways:

.NET Concurrency

16 April 2010 brianbruff

Optimistic Concurrency

In a multiuser environment, there are two models for updating data in a database: optimistic concurrency, and pessimistic concurrency. The DataSet object is designed to encourage the use of optimistic concurrency for long-running activities such as when you are remoting data and when users are interacting with data.

Pessimistic concurrency involves locking rows at the data source to prevent users from modifying data in a way that affects other users. In a pessimistic model, when a user performs an action that causes a lock to be applied, other users cannot perform actions that would conflict with the lock until the lock owner releases it. This model is primarily used in environments where there is heavy contention for data, where the cost of protecting data with locks is less than the cost of rolling back transactions if concurrency conflicts occur.

Therefore, in a pessimistic currency model, a user who reads a row with the intention of changing it establishes a lock. Until the user has finished the update and released the lock, no one else can change that row. For this reason, pessimistic concurrency is best implemented when lock times will be short, as in programmatic processing of records. Pessimistic concurrency is not a scalable option when users are interacting with data, causing records to be locked for relatively large periods of time.

By contrast, users who use optimistic concurrency do not lock a row when reading it. When a user wants to update a row, the application must determine whether another user has changed the row since it was read. Optimistic concurrency is generally used in environments with a low contention for data. This improves performance as no locking of records is required, and locking of records requires additional server resources. Also, in order to maintain record locks, a persistent connection to the database server is required. Because this is not the case in an optimistic concurrency model, connections to the server are free to serve a larger number of clients in less time.

In an optimistic concurrency model, a violation is considered to have occurred if, after a user receives a value from the database, another user modifies the value before the first user has attempted to modify it.

 

LINQPad

16 April 2010 brianbruff

If you've not used nor know what LINQPad is...... tut tut tut

Download it form here

http://www.linqpad.net/  it will make your life easier, infact you'll wonder whatever you did without it...

So how does it help...? try it and see :-)

Declarative Ria Data and Controls

24 March 2010 brianbruff

I'm really loving this declarative approach with silverlight and wpf... (ask me why and I can't tell you ! :-)

Anyway I've just stumbled across a way of managing RiaDataContexts Declaratively
I found it on the Telerik samples.... If you've not looked at these guys controls then check them out!!

 

[code:c#]

<navigation:Page xmlns:dataFormToolkit="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data.DataForm.Toolkit"  xmlns:data="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data"
  x:Class="SiteDocs.Loler"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
  xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
  xmlns:navigation="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Navigation"
  xmlns:telerik="clr-namespace:Telerik.Windows.Controls;assembly=Telerik.Windows.Controls.GridView"
  xmlns:riaControls="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Ria"
  xmlns:e="clr-namespace:SiteDocs.Web.Services"
  xmlns:riaData="clr-namespace:System.Windows.Data;assembly=System.Windows.Controls.Ria"
  mc:Ignorable="d" d:DesignWidth="640" d:DesignHeight="480" 
  Style="{StaticResource PageStyle}"
>

  <Grid x:Name="LayoutRoot" >
    <ScrollViewer x:Name="PageScrollViewer" Style="{StaticResource PageScrollViewerStyle}" >

            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition />
                    <ColumnDefinition />
                </Grid.ColumnDefinitions>
    
    <Grid x:Name="gridLolerLeft" >
     <Grid.RowDefinitions>
      <RowDefinition />
      <RowDefinition Height="Auto"/>
     </Grid.RowDefinitions>

                    <riaControls:DomainDataSource x:Name="DomainDataSource1" AutoLoad="True" QueryName="GetLolers" PageSize="10">
                        <riaControls:DomainDataSource.DomainContext>
                            <e:LolerContext />
                        </riaControls:DomainDataSource.DomainContext>
                        <riaControls:DomainDataSource.FilterDescriptors>
                            <riaData:FilterDescriptorCollection LogicalOperator="Or" />
                        </riaControls:DomainDataSource.FilterDescriptors>
                    </riaControls:DomainDataSource>

                    <telerik:RadGridView x:Name="RadGridView1" ItemsSource="{Binding Data, ElementName=DomainDataSource1}"
                             Filtering="RadGridView1_Filtering" IsBusy="{Binding IsBusy, ElementName=DomainDataSource1}" />
           <telerik:RadDataPager x:Name="RadDataPager1" Grid.Row="1" Source="{Binding Data, ElementName=DomainDataSource1}" DisplayMode="FirstLastPreviousNextNumeric, Text" IsTotalItemCountFixed="True"/>

    
    </Grid>

                </Grid>
    </ScrollViewer>
  </Grid>

</navigation:Page>

[/code]

Expression blend visual states

23 March 2010 brianbruff

A few people have asked me what's the easiest way of doing transitions on Silverlight.

One of the easiest ways has to be to use the VisualStateManager with Expression Blend, see screen show for sample logged in state.
If you don't know how to use this tool then start watching a few vids!

 

To change between states you can use this code..

 

 

[code:c#]

if (WebContext.Current.User.IsAuthenticated)
{
    VisualStateManager.GoToState(this, (WebContext.Current.Authentication is WindowsAuthentication) ? "windowsAuth" : "LoggedIn", true);
}
else
{
    VisualStateManager.GoToState(this, "LoggedOut", true);
}


[/code]

Providing Security in RIA services

23 March 2010 brianbruff

If you wish to prevent clients accessing your data

[code:c#]

[RequiresAuthentication]
[EnableClientAccess()]
public class LolerService : LinqToSqlDomainService<LolerModelDataContext>

[/code]

Popups in wpf

17 March 2010 brianbruff

Here is come code to show a popup in wpf, i've nothing in the popup at the moment, just a gradient background and border.

[code:c#]

<Popup Name="popup1" 
   Width="{Binding ElementName=bdrCalendar, Path=ActualWidth, Converter={StaticResource MarginValueConverter}}"
   Height="150"
   Placement="Center"
   PopupAnimation="Scroll"
   AllowsTransparency="True"
   PlacementTarget="{Binding ElementName=bdrCalendar}"
   MouseDown="popup1_MouseDown" >
 <ctrls:PopupContent />
</Popup>

 

[/code]

 

 

 

RIA Services

15 March 2010 brianbruff

Over the w/end I was helping a mate with his Data-driven Silverlight app.

I was gobsmacked that his developer spent days and weeks writing plumbing code, hand coding infrastructure code and even worse my friend had to pay for it.
Being able to focus on the business needs is important so having a development platform that better enables that focus and increased productivity is an absolute must.

The solution to this problem is codenamed Alexandria i.e. .NET RIA Services, this technology provides a set of server components and ASP.NET extensions that ease the n-tier development process, making your applications almost as easy to develop as if they were running on a single tier, In addition, services such as authentication, roles and profile management are provided. The combination of client and server enhancements to Silverlight 3 and ASP.NET along with the addition of .NET RIA Services, streamline the end-to-end experience of developing data-driven Web applications also known as Rich Internet Applications, or RIAs.

I’m not going to show you how to do it as there are many-many training resources available but a good place to start is here: http://silverlight.net/getstarted/riaservices/

So if you find yourself writing needless plumbing code for a DAL in Silverlight, then spend some time figuring RIA services out!
(Spend some get some diesel for that digger and opposed to grabbing a shovel and diving in!!)

 

 

Filtering data in Silverlight

06 March 2010 brianbruff

Ever want to filter data in Silverlight? here's a simple example that uses a lambda expression to search on name (case sensitive)

 

[code:c#]

ComboBox cbx = ((ComboBox)sender);

ICollectionView dataView =
            CollectionViewSource.GetDefaultView(this.DataContext);
if (!string.IsNullOrEmpty(cbx.Text))
    dataView.Filter = f => ((Job)f).Name.Contains(cbx.Text);
else
    dataView.Filter = null;

[/code]

Cocoa Is My Girlfriend

03 March 2010 brianbruff

Tonight I've stumbled across an interesting Blog on cimgf.

http://www.cimgf.com/2010/02/12/accessing-the-cloud-from-cocoa-touch/#more-909

It's been many years since I wrote PHP, so I'd naturally use asp.net serverside (or if i had a pc powerfull enough I'd use the new REST capabilities of Sharepoint 2010 server).

I've been dying to have a play with Azures for sometime now but I'm always either snowed under with work or playing with some other technology, I remember reading that Azures (storage at least) has a REST API, and with the launch of the iPhone on the Vodafone network at the end of this month I've been looking into what's involved in writing objective C (and some mono stuff) so it seems I may finally get to have a play :-)