Transforming XML containing namespaces

Whenever I get the task of transforming some XML to some other XML using XSL and namespaces are involved it is always a struggle for some reason. And I've experienced that I'm not the only one having problems with that.

Most examples of XML transformation that I stumble over on the web deals with transforming XML to HTML and almost never use namespaces. Therefore I've decided to write a little article where I describe how to transform from XML to XML including the usage of namespaces.

The task

I want to transform an XML document containing information about CDs from one format into another using XSL. The source XML will use one namespace and the output XML another.

Source XML document

This is the source XML document that I want to transform. Notice that it uses the "http://schemas.maze-dev.blogspot.com/2010/catalog" namespace.

<?xml version="1.0" encoding="ISO-8859-1"?>
<catalog xmlns="http://schemas.maze-dev.blogspot.com/2010/catalog">
   <name>Absolute Whatever Vol. 1</name>
   <cd>
       <title>Empire Burlesque</title>
       <artist>Bob Dylan</artist>
       <country>USA</country>
       <company>Columbia</company>
       <price>10.90</price>
       <year>1985</year>
   </cd>
   <cd>
       <title>Hide your heart</title>
       <artist>Bonnie Tyler</artist>
       <country>UK</country>
       <company>CBS Records</company>
       <price>9.90</price>
       <year>1988</year>
   </cd>
   <cd>
       <title>Greatest Hits</title>
       <artist>Dolly Parton</artist>
       <country>USA</country>
       <company>RCA</company>
       <price>9.90</price>
       <year>1982</year>
   </cd>
</catalog>

XSL transformation document

This is the transformation document. The xmlns:xsl="http://www.w3.org/1999/XSL/Transform" defines the standard 'xsl' transform namespace. However, the interesting part is xmlns="http://schemas.maze-dev.blogspot.com/2010/archive" which defines the output namespace (i.e. namespace in output XML) and xmlns:cat="http://schemas.maze-dev.blogspot.com/2010/catalog" which defines the namespace 'cat' used to reference elements in the input XML. The attribute exclude-result-prefixes="cat" states that the 'cat' namespace should not be included in the output XML.

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0" 
        xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
        xmlns="http://schemas.maze-dev.blogspot.com/2010/archive"
        xmlns:cat="http://schemas.maze-dev.blogspot.com/2010/catalog" exclude-result-prefixes="cat">
    <xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>

    <xsl:template match="/">
        <archive>
            <xsl:apply-templates select="cat:catalog"/>
        </archive>
    </xsl:template>
    <xsl:template match="cat:catalog">
        <name><xsl:value-of select="cat:name"/></name>
        <xsl:apply-templates select="cat:cd"/>
    </xsl:template>
    <xsl:template match="cat:cd">
        <album>
            <title>Title: <xsl:value-of select="cat:title"/></title>
            <artist>Artist: <xsl:value-of select="cat:artist"/></artist>
        </album>
    </xsl:template>
</xsl:stylesheet>

Output XML document

This is the output XML document. Notice that it uses the "http://schemas.maze-dev.blogspot.com/2010/archive" namespace that was specified in the XSL document.

<?xml version="1.0" encoding="UTF-8"?>
<archive xmlns="http://schemas.maze-dev.blogspot.com/2010/archive">
    <name>Absolute Whatever Vol. 1</name>
    <album>
        <title>Title: Empire Burlesque</title>
        <artist>Artist: Bob Dylan</artist>
    </album>
    <album>
        <title>Title: Hide your heart</title>
        <artist>Artist: Bonnie Tyler</artist>
    </album>
    <album>
        <title>Title: Greatest Hits</title>
        <artist>Artist: Dolly Parton</artist>
    </album>
</archive>

So basically, that's it. Hope somebody finds it useful.

"Specified Cast is Not Valid" - LinqToSql error on submit

While working on a project using LinqToSql I got the error "Specified Cast is Not Valid" when calling SubmitChanges.

After searching a bit on the web I found out the error is due to a problem in .NET Framework 3.5. Luckily there is a hotfix that addresses this problem. Here are some articles about the problem:

http://connect.microsoft.com/VisualStudio/feedback/details/351358/invalidcastexception-on-linq-db-submit-with-non-integer-key

http://rexcitations.wordpress.com/2009/08/15/specified-cast-is-not-valid-error-using-linq-with-foreign-keys/

http://www.mha.dk/category/SQLDatabase.aspx

The first article is very specific:

"When database contains two tables, both with automatic integer primary keys, and a relationship between a unique char field in one and a non-unique char field in the other, inserting new rows into the second table fails on submit with InvalidCastException."

This is a bit too specific as to the usage of int and char, because the error occurs in other situations as well which can be seen in the second article. Here the error occurs using GUID and int. And to top that up, in my own situation the error occurred using int and long.

The third article has a link from which to download a hotfix to solve the problem.

If you want to obtain the hotfix in a more official way you can use this link:

http://support.microsoft.com/hotfix/KBHotfix.aspx?kbnum=963657&kbln=en-us

DataGridView with Typed DataSet

I was recently working on an assignment creating a Windows Forms application with a DataGridView being fed data from some object collection, and NOT (as is the case with virtually all samples that can be found on the Internet) using the SqlDataAdapter.

Even though this is a pretty simple task once you've found out how to do it, I did find it a bit tricky to get to work. So here's how it can be done.

1. Start Visual Studio and create a new Windows Forms application.
2. Add a DataSet to the project by right-clicking on the project and selecting Add -> New Item and selecting the DataSet template naming it ContactDataSet. This should bring up the DataSet designer.
3. Add a new DataTable to the designer area using the Toolbox. Name it Contact and add some columns to table (see details such as column data types in the sample code)
   
4. Add a new class to the project and name it Address:
   

   
   public class Address
   {
       public long Id { get; set; }
       public string Street { get; set; }
       public int HouseNumber { get; set; }
       public string PostalCode { get; set; }
       public string PostalDistrict { get; set; }
   }
   

   
   
5. Add another new class to the project and name it Contact:
   

   
   public class Contact
   {
       public long Id { get; set; }
       public string FirstName { get; set; }
       public string LastName { get; set; }
       public int? Age { get; set; }
       public Address Address { get; set; }
   }
   

   
   


6. In Form1.cs add this private member:
   

   
   private ContactDataSet _contactDataSet = new ContactDataSet();
   

   
   


7. Also in Form1.cs add this method for generating a collection of test data:
   

   
   private IList<Contact> GenerateData()
   {
       IList<Contact> contactList = new List<Contact>();
       contactList.Add(new Contact
       {
           Id = 1,
           FirstName = "Peter",
           LastName = "Jackson",
           Age = 53,
           Address = new Address
           {
               Street = "Long Road",
               HouseNumber = 173,
               PostalCode = "12345",
               PostalDistrict = "Fake Town"
           }
       });
       contactList.Add(new Contact
       {
           Id = 2,
           FirstName = "Pavlov",
           LastName = "Ivanowich",
           Address = new Address
           {
               Street = "Park Avenue",
               HouseNumber = 1011,
               PostalCode = "98765",
               PostalDistrict = "Imaginaryville"
           }
       });
       contactList.Add(new Contact
       {
           Id = 3,
           FirstName = "Onslow",
           LastName = "Bucket",
       });
       return contactList;
   }
   

   
   
8. Furthermore, add this method for filling the DataSet with data from a collection:
   

   
   private void FillDataSet(IList<Contact> contactList)
   {
       foreach (Contact contact in contactList)
       {
           ContactDataSet.ContactRow row = _contactDataSet.Contact.NewContactRow();
           row.FirstName = contact.FirstName;
           row.LastName = contact.LastName;
           if (contact.Age.HasValue)
           {
               row.Age = contact.Age.Value;
           }
           if (contact.Address != null)
           {
               row.Street = contact.Address.Street;
               row.HouseNumber = contact.Address.HouseNumber;
               row.PostalCode = contact.Address.PostalCode;
               row.PostalDistrict = contact.Address.PostalDistrict;
           }
           _contactDataSet.Contact.AddContactRow(row);
       }
   
       // OK, so we have filled in the data we want to start up with.
       // We must now call AcceptChanges so that this data isn't change-tracked.
       _contactDataSet.AcceptChanges();
   }
   

   
   
9. Go to the Form Designer and add a BindingSource and name it contactBindingSource. Set the ContactDataSet as DataSource and Contact as DataMember.
10. In the Form Designer also add a DataGridView and set contactBindingSource as DataSource.
    
11. In the Form1.cs add this code in the Load event handler:
    

    
    IList<Contact> contactList = GenerateData();
    FillDataSet(contactList);
    
    contactBindingSource.DataSource = _contactDataSet;
    

    
    
12. Run the application. The DataGridView should now display the test data.