Shawn Wildermuth

Author, Teacher, and Filmmaker
.NET Foundation Board Member

Things About Typed DataSet Generation I Never Noticed...

Things About Typed DataSet Generation I Never Noticed...

I have been thinking a lot about how Typed DataSets are generated and was spelunking through the code again when it got me thinking. The Typed DataSet generator doesn't really generate the code based on the .xsd, but on the DataSet. It simply loads the .xsd into a DataSet then interrogates the DataSet directly for everything (tables, columns, relationships, constraints). So if the Typed DataSet Designer cannot handle something (like relationships *without* constraints, see below), but the DataSet schema allows it...simply create the DataSet and save the .xsd file to see what it produces! This gets around some fundamental problems with the designer. It does require you start looking and understanding .xsd, but it is a useful skill to have anyway...right?

So my first relevation was how to add unconstrained relationships (no foreign key constraint, simply a way to navigate the data). Since the designer does not allow this, I looked at the .xsd and found that the DataSet handles this with a schema annotation:


<xs:schema>
  <xs:annotation>
    <xs:appinfo>
      <msdata:Relationship name="ta2t" 
        msdata:parent="titleauthor" 
        msdata:child="titles" 
        msdata:parentkey="title_id"
        msdata:childkey="title_id" />
    </xs:appinfo>
  </xs:annotation>
</xs:schema>

The five pieces of data in the msdata:Relationship element are the four pieces of data required when setting up a relationship. Pretty simple huh!

It makes me start to think of other DataSet allowable things that the Designer doesn't know about.