Element Operators Query Expression Syntax Examples (LINQ to DataSet)
The examples in this topic demonstrate how to use the First and ElementAt<TSource> methods to get DataRow elements from a DataSet using the query expression syntax.
The FillDataSet method used in these examples is specified in Loading Data Into a DataSet.
The examples in this topic use the Contact, Address, Product, SalesOrderHeader, and SalesOrderDetail tables in the AdventureWorks sample database.
The examples in this topic use the using/Imports statements found in Query Expression Examples (LINQ to DataSet).
For more information, see How to: Create a LINQ to DataSet Project In Visual Studio.
ElementAt
Example
This example uses the ElementAt<TSource> method to retrieve the fifth address where PostalCode == "M4B 1V7".
' Fill the DataSet.
Dim ds As New DataSet()
ds.Locale = CultureInfo.InvariantCulture
' See the FillDataSet method in the Loading Data Into a DataSet topic.
FillDataSet(ds)
Dim addresses As DataTable = ds.Tables("Address")
Dim fifthAddress = ( _
From address In addresses.AsEnumerable() _
Where address.Field(Of String)("PostalCode") = "M4B 1V7" _
Select address.Field(Of String)("AddressLine1")).ElementAt(5)
Console.WriteLine("Fifth address where PostalCode = 'M4B 1V7': " & _
fifthAddress)
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable addresses = ds.Tables["Address"];
var fifthAddress = (
from address in addresses.AsEnumerable()
where address.Field<string>("PostalCode") == "M4B 1V7"
select address.Field<string>("AddressLine1"))
.ElementAt(5);
Console.WriteLine("Fifth address where PostalCode = 'M4B 1V7': {0}",
fifthAddress);
First
Example
This example uses the First method to return the first contact whose first name is 'Brooke'.
' Fill the DataSet.
Dim ds As New DataSet()
ds.Locale = CultureInfo.InvariantCulture
' See the FillDataSet method in the Loading Data Into a DataSet topic.
FillDataSet(ds)
Dim contacts As DataTable = ds.Tables("Contact")
Dim query = ( _
From contact In contacts.AsEnumerable() _
Where contact.Field(Of String)("FirstName") = "Brooke" _
Select contact).First()
Console.WriteLine("ContactID: " & query.Field(Of Integer)("ContactID"))
Console.WriteLine("FirstName: " & query.Field(Of String)("FirstName"))
Console.WriteLine("LastName: " & query.Field(Of String)("LastName"))
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable contacts = ds.Tables["Contact"];
DataRow query = (
from contact in contacts.AsEnumerable()
where (string)contact["FirstName"] == "Brooke"
select contact)
.First();
Console.WriteLine("ContactID: " + query.Field<int>("ContactID"));
Console.WriteLine("FirstName: " + query.Field<string>("FirstName"));
Console.WriteLine("LastName: " + query.Field<string>("LastName"));
See Also
Concepts
Standard Query Operators Overview