Question

I am looking at several XSD files that use msdata:Ordinal for the elements within a sequence. I can’t seem to find anywhere what this is used and/or in what circumstances this would be needed. Can somebody help me out with an explanation and example?

Answer 1

I was wondering the same thing. *.xsd files generated by xsd.exe or using DataSet.WriteXmlSchema tend to have this attribute, as defined in msdata.xsd in your “<VS folder>\Microsoft Visual Studio *\Xml\Schemas” folder:

...
    <xs:attribute name="Ordinal" type="xs:integer">
    </xs:attribute>
...

The attribute is used to define ordinal position of a column, which is useful for mapping the xsd schema to a DataSet.
See: Deriving DataSet Relational Structure from XML Schema (XSD), Using XML in a DataSet

This article briefly talked about it:

An extra attribute named Ordinal has been created. As always, it is a
part of the msdata space, with a value of 0 for the first column, and
1 for the second column. This is by virtue of each column being
assigned a number starting with zero and then, progressively
increasing it by one.