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Silverlight Cross Domain Web Service Access Error - This could be due to attempting to access a service in a cross-domain way without a proper cross-domain policy in place

by Admin 9. March 2010 08:46

Here is some error that most of Silverlight developers run into at some point.


An error occurred while trying to make a request to URI 
'http://nave-pc/SilverGridWeb/GridDataService.asmx'.
This could be due to attempting to access a service in a cross-domain way 
without a proper cross-domain policy in place, or a policy that is unsuitable 
for SOAP services. You may need to contact the owner of the service to publish 
a cross-domain policy file and to ensure it allows SOAP-related 
HTTP headers to be sent. This error may also be caused by using internal types 
in the web service proxy without using the InternalsVisibleToAttribute attribute. 
Please see the inner exception for more details.

I had developed cross-domain access web services for Silverlight in the past and all work like a charm. This morning I ran into this issue again while developing a new web service for a new Silverlight application. I knew that I needed to add CrossDomain.xml or ClientAccessPolicy.xml at root of my web application. So I copied those files from existing application to this new one. To my surprise it did not resolve the issue. I tried all kind of tricks and options but nothing seemed to help. Finally I decided to look at Silverlight documentation and see if there is anything new that has been done for Silverlight 3. Last time I did this was for a Silverlight 2.0 application. I could not find anything different in the description of what needed to be done. But then there was something in the sample XML file content for these files that caught my eye and looked different that what I had.


<allow-from http-request-headers="SOAPAction" >

Notice the underlined section. Previously the value in the allowed headers used to be *. Well, that does not seem to work any more. So I replaced it and everything worked fine.

There are some other important points I am going to discuss in this post. A lot of users do not seem to be clear where these cross domain policy files should be placed.

Location of CrossDomain.xml and ClientAccessPolicy.xml

As the documentation states, these should be placed at the root of the application. Although the statement is very clear but it causes lot of confusion about what is root? There are two ways you create a site in IIS, Virtual Directory and Web Application. So if you have a web site foo.com created as a web site in IIS, then the folder containing the content of this site is root of the application. So your policy files go in that folder. If you have created a virtual directory Bar under this web site where your web service is hosted, then the root of the site is still foo.com and not foo.com/bar. To verify it, open IIS log of your application and look for entries for Crossdomain.xml and ClientAccessPolicy.xml. From those entries you can figure out where those files should be located. If the caller is not finding those files, then you should 404 errors in your log file. For example here are entries from my log file.


1.17.30.170 GET /clientaccesspolicy.xml - 80 - 1.17.30.162  404 0 2 1
1.17.30.170 GET /crossdomain.xml - 80 - 1.17.30.162 404 0 2 1

This is very important. If you are hosting your web service in a web application that is created as a virtual directory in Default Web Site then you need to copy these files in wwwroot folder or whatver folder is configured to be default folder for your IIS installation. Copying policy files in your virtual directory is not going to help. You can also verify the location by looking at traffic in fiddler for your web service access.

Content for CrossDomain.xml and ClientAccessPolicy.xml

I have copied the content of these two files below. These files work for me on my my servers for cross domain access from silverlight.

ClientAccessPolicy.xml


<?xml version="1.0" encoding="utf-8"?>
 <access-policy>
  <cross-domain-access>
  <policy>
  <allow-from http-request-headers="SOAPAction ">
  <domain uri="*"/>
  </allow-from>
  <grant-to>
  <resource path="/" include-subpaths="true"/>
  </grant-to>
  </policy>
 </cross-domain-access>
</access-policy>

CrossDomain.xml


<?xml version="1.0"?>
<!DOCTYPE cross-domain-policy SYSTEM "http://www.macromedia.com/xml/dtds/cross-domain-policy.dtd">
<cross-domain-policy>
 <allow-http-request-headers-from domain="*" headers="SOAPAction,Content-Type"/>
</cross-domain-policy>

Views: 78

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Silverlight | Web Service

How to add paging to DataGrid in Silverlight

by Admin 24. February 2010 10:37

Download Sample Project (367.89 kb)

paging in silverlight datagrid

In one of my previous posts How to use DataGrid in Silverlight I showed a very simple usage where data grid was bound to a list of products. Now let us take one more step in customizing use of this data grid. When I executed my method to get list of products from AdventureWorks database, it returned me about 1000 records. And then datagrid was bound to that list, i got a huge page with grid showing all the records. I am sure at this point you are looking for way to add some kind of paging to your data grid so that user can navigate the list easily.

Silverlight has a control named DataPager that comes in very handy to add paging functionality to any control that you use to display lists. From the name is it obvious that this control is a pager. Following XAML shows how I added paging functionality to my datagrid.


<StackPanel x:Name="ContentStackPanel" Orientation="Vertical">
 <TextBlock x:Name="HeaderText" Style="{StaticResource HeaderTextStyle}" 
     Text="Products"/>
  <data:DataPager x:Name="ProductsPager" 
    PageSize="10" 
    DisplayMode="Numeric" 
    AutoEllipsis="True" 
    HorizontalAlignment="Left" />
  <data:DataGrid x:Name="ProductsGrid">
   <data:DataGrid.Columns>
   <data:DataGridTemplateColumn>
   <data:DataGridTemplateColumn.CellTemplate>
   <DataTemplate>
   <StackPanel>
   <Button x:Name="UpdateButton" Content="Update" 
     Click="UpdateButton_Click"></Button>
   </StackPanel>
   </DataTemplate>
   </data:DataGridTemplateColumn.CellTemplate>
   </data:DataGridTemplateColumn>
   </data:DataGrid.Columns>
   </data:DataGrid>
</StackPanel>

You can read more about different ways to customize the display of datapager from the documentation. For this discussion you can see that I have set PageSize, DisplayMode, AutoEipsis and HorizontalAlignment properties of pager and the screen shot shows how it looks. I will talk more about customization of DataPager in detail in next post. For now I just want to keep it to simple use.

PageViewCollection

This is the collection object that drives the functionality for DataPager. In general you need a collection that implements IPagedViewCollection interface. No, you do not have to do any more implementation to get DataPager to work. We already have list of products obtained from previous web service call. You can simply wrap that list into PagedViewCollection object and set it as Source for DataPager object. And then set the source for DataGrid as this PagedViewCollection object and we are all set to go. Following code shows simple change I made in code from previous sample project.


void GetProductsCompleted(object sender, GetProductsCompletedEventArgs e)
{
 _products = e.Result;
 if (null != _products)
 {
  _pagedProductsView = new PagedCollectionView(_products);
  ProductsPager.Source = _pagedProductsView;
  ProductsGrid.ItemsSource = _pagedProductsView;
 }
}

Add References

PagedViewCollection is defined in System.Windows.Data assembly. So you will need to add reference to this assembly in your Silverlight project and then add using directive for the namespace in your source code to refer to the classes in this namespace and assembly.

Adding Paging to DataGrid in Silverlight is as easy as that.

Views: 216

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DataGrid | Silverlight

How to use DataGrid in Silverlight?

by Admin 5. February 2010 07:49
DataGrid is one of the most important control when it comes to displaying tabular kind of data. We all implement rendering of such data in some of table format. Developers who has been using ASP.Net are very familiar with controls like DataGrid and GridView. Good news is that there is equivalent DataGrid control for Silverlight as well. And for most part it is used the same way as you do in ASP.Net but with different syntax and different way of customizing display of it. In this post I am going to show a very plain and simple use of DataGrid control in Silverlight and then in subsequent posts I will build on top of this post to show some more advanced uses of DataGrid control.

Silverlight Tool Kit

You may already know this and already has it on your development machine, but I will mention it for sake of completness. You are going to need Silverlight Toolkit to use DataGrid. Yes, the control is not part of core Silverlight. Microsoft has developed it as part of the tool kit that has lot of usefull controls. You can read more about this tool kit and controls on the site. For now, down the toolkit and install it on your machine.

Reference assemblies

In your Silverlight project, you will need to add reference to System.Windows.Controls.Data assembly. This is the assembly where DataGrid control is defined. Now you can include DataGrid control on your XAML file. If you tried to add mark up like below on your page, you are going to get error telling you that DataGrid is not recoganized.


<DataGrid x:Name="MyGrid" />

You have to treat DataGrid control like a UserControl in ASP.Net where you have to specify a tag prefix and assembly on top of your page to indicate use of that control. In Silverllight you do this my including xml namespace tag for that silverlight control. In my case I have the following xmlns entry on my XAML file.


xmlns:data="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data"

This tells the application that I am going to use prefix data for the controls that are present in assembly System.Windows.Controls.Data. Based on this you can now add the following like of mark up on XAML file to include DataGrid on your page.


<data:DataGrid 
  x:Name="CommentsGrid" 
  Height="300" 
  AutoGenerateColumns="True" 
  IsReadOnly="True">
</data:Grid>

Attach To Data Source

Now that we have included DataGrid control on the page, we need to attach it to some data source to show some results. Very much like ASP.Net, you will attach an enumeration to this control. The difference is that here it is done through property name ItemSource. Following line of code shows how it is done for silverlight DataGrid control.


List _unmoderatedComments = new List();

void BindGrid()
{
 CommentsGrid.ItemsSource = _unmoderatedComments;
}

As you can see that DataGrid is bound to a List of Comment objects. So far so good, very much like your ASP.Net DataGrid or GridView.

Columns to Display

In the mark of DataGrid above, I have explcitly set AutoGenerateColumn property to true. This actually is default value. What this means is that when DataGrid is bound to the collection, it will generate column for each data field or property for the objects in the collection and display them. Thsi is same behavior you see in ASP.Net data grid.

Explcitly specifying Columns

When you are dealing with some real application most of the time you control the columns you want to display and how you want to display them. Silverlight DataGrid does allow you to do so. Fisrt, you will set AutoGenerateColumns property to false. Following mark up shows how you will specify the columns that you want to display.


<data:DataGrid x:Name="CommentsGrid" Height="300" 
  AutoGenerateColumns="False" IsReadOnly="True">
 <data:DataGrid.CellStyle>
  <Style TargetType="data:DataGridCell">
  <Setter Property="VerticalAlignment" Value="Top"></Setter>
  </Style>
 </data:DataGrid.CellStyle>
 <data:DataGrid.Columns>
  <data:DataGridTextColumn Header="Comment Date" 
    Binding="{Binding CommentDate}"></data:DataGridTextColumn>
  <data:DataGridTextColumn Header="Comment Text" Binding="{Binding Text}">
  <data:DataGridTextColumn.ElementStyle>
  <Style TargetType="TextBlock">
   <Setter Property="TextWrapping" Value="Wrap"/>
  </Style>
  </data:DataGridTextColumn.ElementStyle>
 </data:DataGridTextColumn>
 <data:DataGridTemplateColumn>
  <data:DataGridTemplateColumn.CellTemplate>
   <DataTemplate>
    <StackPanel Orientation="Horizontal">
     <Button x:Name="ApprovedButton" Content="Approved" 
       Click="ApprovedButton_Click" Height="30" Margin="3"></Button>
     <Button x:Name="DeleteButton" Content="Delete" 
        Click="DeleteButton_Click" Height="30" Margin="3"></Button>
     <Button x:Name="SpamButton" Content="Mark Spam" 
       Click="SpamButton_Click" Height="30" Margin="3"></Button>
   </StackPanel>
   </DataTemplate>
  </data:DataGridTemplateColumn.CellTemplate>
 </data:DataGridTemplateColumn>
 </data:DataGrid.Columns>
</data:DataGrid>

You will need to add Columns section under your DataGrid control definition and then specify each column that you would want to display. And to bind the column to particular property or field, you will use Binding property. For this post I am going to keep the dicussion to simple binding of the column to property of the object. I will discuss more advanced use in subsequent posts. You can see it is very similar to how you are used to doing things in ASP.Net.

And to accomodate more customized view of the column, you will use DataGridTemplateColumn where you can layout the template of the view of that column. This is also similar to template column in ASP.Net.

More...

For this post I am going to leave this discussion to this simple display of data. I will be discussing more about use of Silverlight DataGrid in subsequent posts. This post should get you started with use of it now.

Views: 598

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DataGrid | Silverlight

How to add pushpin and datagrid to Bing Map Silverlight control

by Admin 6. January 2010 07:58
Bing map silverlight control sdk

In one of my earlier posts Convert IP Addresss To Geo Location, I discussed how you can query a web service or database to get geo-location of that internet service provider. Now what do you do with that geo-location or spatial information. For one of the current Data Visualization projects I am working on, I had to show these locations on the map as well. The application is a Silverlight application so obvious choice was to find a control or component that I could drop in silverlight. And you pretty much have the answer, Use Bing Map Silverlight Control.

In this post I am going to discuss some of the following topics.

  • How to use Bing Silverlight Map Control?
  • How to add push pins to bing map?
  • How to add legends or some text to Silverlight Bing Map?
  • How to add regular silverlight controls on Bing Map control?

The documentation for Bing Map Silverlight control is still maturing and lacks lot of details. So most of the discussion in this post is based on personal experience and conversations I had through news groups and forums.

Set up development enviroment

Before you can start developing your silverlight application using Bing Map Silverlight control, you will need to do following things.

  • Create a developer account at Bing portal
  • As part of registration process, you will also be required to a credential key that is used with each request that you send to Bing web service to access data.
  • Download Bing Map Control SDK and install on your development machine.

Create Project and lets roll

Microsoft has provided a good walk through on Creating a Basic Application Using the Silverlight Map Control. I will strongly recomment going through it if its first time for you in Bing Map development.

Adding PushPin to Bing Map

Now that you have a vanilla implementation of map showing in your application. Next I want to add indicztors on the map to show location of internet service providers for which I have geo corodinates. There are few ways you can do. The most basic thing that you need to keep in mind is that Bing Map control is like any other silverlight control and can act as a container for other silverlight control. That means that I can just draw any shapes or objects at given corodinates. Well, you got it. Bing Map SDK provides some of these indicator controls out of the box. And one of them is PushPin. So what you need to do is crate instances of PushPin objects, set their longitude and latitude and add them as children of map control. Following code snippet shows how I added a collection of PushPin objects to my map control.

foreach(var loc in locations)
{
	var pp = new Pushpin() 
	  {Location = new Location(loc.Latitude, loc.Longitude)};
	UserLocationsMap.Children.Add(pp);
}

Adding DataGrid to Bing Map

Next task I had to do was to provide some summary of the data on the map itself. More precisely, I wanted to show how many service provides from each country I have in my database. For demo purposes I just needed to show name and count. I decided to add a DataGrid to map to show this data. Later on I am going to handle click events in this grid to have some interaction with the map as well. Since I already knew where I wanted to place the grid and what columns needed to be shown, I could just add this through XAML file itself. Following XAML snippet from the application shows how I have added a text block and data grid to Bing Map control as children.


<m:Map CredentialsProvider="xxxxxxxxxx" Name="UserLocationsMap">
 <m:Map.Children>
  <o:ShadowText x:Name="MapTitleText" ForegroundTop="Black" ForegroundBottom="Orange"
      Text="ISP Locations" FontFamily="Verdana" FontSize="24"
      HorizontalAlignment="Left" Margin="20,75,50,10"/>
	<StackPanel x:Name="CountryListPanel" Margin="20,250,50,10" Orientation="Vertical">
	 <data:DataGrid x:Name="CountryCountGrid" Width="150" Height="250"
	   AutoGenerateColumns="False" HorizontalAlignment="Left">
	  <data:DataGrid.Columns>
	   <data:DataGridTextColumn Header="Country" Width="SizeToHeader" Binding="{Binding Name}" />
	   <data:DataGridTextColumn Header="Count" Width="SizeToHeader" Binding="{Binding Count}" />
	  </data:DataGrid.Columns>
	 </data:DataGrid>
	</StackPanel>
	</m:Map.Children>
</m:Map>

Postioning on Map control

This is something you will have to play very close attention to. There is a difference between how controls or objects placed on map control. You must have noticed that when I added PushPin to map, I used longitude and latitude to position them on the map. But when I added DataGrid and ShadowText controls, I used Margin to control the placement. Most of the indiccator or layer objects that are provided in Bing Map SDK use gro-location values (longitude and latitude) to place object. But when you add regular silverlight controls on map, then you will control the position using Margin relative to origin of map control.

Views: 1162

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Silverlight | Bing Map

How to send data from Javascript on page to Silverlight control

by Admin 1. August 2009 05:08

Download Demo Project

I have been discussing use of jQuery to send AJAX request to server to get some data every X number of seconds to get server time and calculate some latency numbers. Now it is time to add some color to it. The numbers that I am getting is great and provide some useful information. But having a visual of how these numbers are varying with time will enhance utility of these statistics. So I decided to add some charts to show these latency numbers are varying with time. In this article I am going to show how you can pass the data obtained from server using AJAX request to a Silverlight application hosted on the page. This silverlight application uses charting control from Silverlight toolkit. Lets see how all this fits together to get this to work.

Bridge between Javascript and Silverlight component

In one of earlier posts, How to setup communication between silverlight applications, I discussed how you set this bridge up. The sample project for that article was done using Silverlight 2. The mechanism to set up the communication bridge has not changed in Silverlight 3. So all those concepts still apply for this project as well. The following code snippets shows declaration of a method decorated with ScriptableMember attribute to let silverlight framework know that this methos is to be exposed to javascript. And in constructor of the page, HtmlPage.RegisterScriptableObject method is called to register the class to be exposed to javascript. I do not want to expose all my properties, fields and methods to javascript. So I have not added scriptable attribute on class itself. I want to control what is exposed and what is not.


public MainPage()
{
	InitializeComponent();
	HtmlPage.RegisterScriptableObject("ClockDataClient", this);
	SetupChartDisplay();
}
		
[ScriptableMember]
public void PutNewClockData(string xtx, string data)
{
	AddDataPointToPlot(data);
}

This completes what needed to be done from silverlight application to expose its end points to javascript. Now we are going to see what is done on pages to communicate to silverlight control.

Setting up the page

First thing you need on the page is to include your Silverlight control. On Default.aspx you will find the following declaration of object tag that will host the control.


<object id="clockDisplayPlugin" data="data:application/x-silverlight-2," 
  type="application/x-silverlight-2" width="100%" height="100%">
<param name="source" value="ClientBin/ClockLatency.xap"/>
<param name="onError" value="onSilverlightError" />
<param name="onLoad" value="onLoadClockDisplay" />
<param name="background" value="white" />
<param name="minRuntimeVersion" value="3.0.40624.0" />
<param name="autoUpgrade" value="true" />
<a href="http://go.microsoft.com/fwlink/?LinkID=149156&v=3.0.40624.0" style="text-decoration:none">
  <img src="http://go.microsoft.com/fwlink/?LinkId=108181" alt="" style="border-style:none"/>
</a>
</object>

All this code was generated by wizard when I added test paste to my project. I added a new param declaration to handle load event. This event is fired when Silverlight control has been loaded. On lets see what all javascript is required to send message to silverlight control.


function onLoadClockDisplay(sender, args) {
 objClockDisplay = sender.getHost();
}

function sendLatencyData(data) {
 if (null != objClockDisplay) {
  objClockDisplay.Content.ClockDataClient.PutNewClockData("", data);
 }
}

As you can see, in load event handler I saved the reference to Silverlight control object. Then from my ajax request code, every time I got the data from server, I call sendLatencyData method. This method calls PutNewClockData method that I exposed from control using ScriptableMember attribute. This call constitutes of four parts.

objClockDisplay.Content.ClockDataClient.PutNewClockData

objClockDisplay is reference to our silverlight plugin. Content is the property on plug-in object through which control's methods are exposed. ClockDataClient is the key that was used to register the class as scriptable in our control. PutNewClockData is the name of the method.

Setting up charting control in Silverlight component

I used charting control from Silverlight Toolkit for my project. I decided to use column chart to display latency numbers over time. In silverlight application project, I added the following XAML on MainPage.


<chartingToolkit:Chart Title="Clock Latency" x:Name="latencyChart" BorderThickness="2">
 <chartingToolkit:Chart.Series>
  <chartingToolkit:ColumnSeries Title="Latency" DependentValueBinding="{Binding Latency}" AnimationSequence="Simultaneous" />
 </chartingToolkit:Chart.Series>
</chartingToolkit:Chart>

In code behind i created a collection to save data sent from javascript and attached the column series to that collection. I only keep last 11 entries in the collection.


void SetupChartDisplay()
{
 ColumnSeries cs = latencyChart.Series[0] as ColumnSeries;
 foreach(var lItem in cs.LegendItems)
 {
  lItem.Visibility = System.Windows.Visibility.Collapsed;
 }

 latencyChart.Width = 500;
 (latencyChart.Series[0] as DataPointSeries).ItemsSource = DynamicCollectionItemsSource;
}

You can see it was pretty simple to set this whole up and get javascript to send data to silverlight control and render the charts using those numbers.

Click to see demo

Views: 1379

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JavaScript | JQuery | Silverlight