Datasheet

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Chapter 1: Project LINQ

XQuery, or Extensible Stylesheet Language Transformations (XSLT). For example, to read an XML

document using existing technology, you would need to do something like the following:

XmlTextReader rdr = new XmlTextReader("C:

Employees.Xml");

while (rdr.Read())

{

XmlNodeType nt = rdr.NodeType;

Switch (nt)

{

case XmlNodeType.Element:

break;

case XmlNodeType.Attribute:

break;

case XmlNodeType.Comment:

break;

case XmlNodeType.Whitespace:

break;

}

That’s a lot of code just to read an XML document (and it isn’t even complete). Writing XML isn’t any

less confusing, as illustrated here:

XmlTextWriter wrt = new XmlTextWriter("C:

Employees.Xml");

wrt.WriteStartDocument;

wrt.WriteComment("This is an example");

wrt.WriteStartElement("Employees");

wrt.WriteStartElement("Employee");

wrt.WriteStartElement("FirstName");

wrt.WriteString("Scott");

wrt.WriteEndElement();

Visually, you don’t know if this will work until you compile the project. Likewise, it is hard to see what

the resulting XML will look like.

XML is great and its use continues to grow; you can expect it to be around for a long time. Yet, truth be

told, XML is still hard to work with.

In dealing with these hurdles, Microsoft considered two paths. The ﬁrst path would have required the

company to build speciﬁc XML or relational data features into each programming language and run-time.

That would be a major undertaking and an even bigger hassle to maintain. The second option was to add

more general-purpose query capabilities into the .NET Framework—in other words, a framework of

all-purpose querying facilities built into the .NET Framework that both C# and VB.NET could easily take

advantage of.

Luckily, Microsoft chose the later option, creating a uniﬁed query experience across objects, XML,

collections, and data. It accomplished that by taking query set operations, transforms, and constructs and

bringing them to the surface, making them high-level concepts within the .NET Framework (for example,