C# 5.0 Programmer's Reference

770 ❘ Appendix J LINQ
(continued)
Function
Nodes
NodesAfterSelf
NodesBeforeSelf
Returns
IEnumerable containing the nodes that are immediate children
of the element. These include all nodes such as XElement
and XText.
IEnumerable containing the sibling nodes of the element that
come after this element.
IEnumerable containing the sibling nodes of the element that
come before this element.
LINQ to ADO.NET
LINQ to ADO.NET provides tools that enable you to apply LINQ-style queries to objects used by
ADO.NET to store and interact with relational data. LINQ to ADO.NET includes three components:
LINQ to SQL, LINQ to Entities, and LINQ to DataSet.
Building and managing SQL Server databases and the Entity Framework are topics too large to
cover in this book, so LINQ to SQL and LINQ to Entities are not described in more detail here.
For more information, consult the online help or Microsoft’s website.
LINQ to DataSet lets a program use LINQ-style queries to select data from DataSet objects.
For example, suppose the testScoresDataSet object contains tables named Students and
TestScores. Then the following code gets references to the DataTable objects that represent
the tables.
DataTable studentsTable = testScoresDataSet.Tables["Students"];
DataTable scoresTable = testScoresDataSet.Tables["TestScores"];
You can then use LINQ to query the DataTable table objects. For example, the following code selects
the names of students with LastName before "F" alphabetically.
var namesBeforeFQuery =
from student in studentsTable.AsEnumerable()
where (student.Field("LastName").CompareTo("F") < 0)
orderby student.Field("LastName")
select new
{
FirstName = student.Field("FirstName"),
LastName = student.Field("LastName")
};
namesBeforeDDataGrid.DataSource = namesBeforeFQuery.ToList();
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