Method-Based Query Syntax Examples: Conversion Operators (LINQ to DataSet)

The examples in this topic demonstrate how to use the ToTSource>, ToDictionary, and ToList<TSource> methods to immediately execute a query expression.

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 following using/Imports statements:

Option Explicit On

Imports System
Imports System.Linq
Imports System.Linq.Expressions
Imports System.Collections.Generic
Imports System.Data
Imports System.Data.SqlClient
Imports System.Data.Common
Imports System.Globalization

using System;
using System.Linq;
using System.Linq.Expressions;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Data.Common;
using System.Globalization;

For more information, see How to: Create a LINQ to DataSet Project In Visual Studio.

ToArray

Example

This example uses the ToTSource> method to immediately evaluate a sequence into an array.

' 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 products As DataTable = ds.Tables("Product")

Dim productsArray = products.AsEnumerable().ToArray()

Dim query = _
        From product In productsArray _
        Select product _
        Order By product.Field(Of Decimal)("ListPrice") Descending

Console.WriteLine("Every price From highest to lowest:")
For Each product In query
    Console.WriteLine(product.Field(Of Decimal)("ListPrice"))
Next

// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);

DataTable products = ds.Tables["Product"];

IEnumerable<DataRow> productsArray = products.AsEnumerable().ToArray();

IEnumerable<DataRow> query =
    from product in productsArray
    orderby product.Field<Decimal>("ListPrice") descending
    select product;

Console.WriteLine("Every price from highest to lowest:");
foreach (DataRow product in query)
{
    Console.WriteLine(product.Field<Decimal>("ListPrice"));
}

ToDictionary

Example

This example uses the ToDictionary method to immediately evaluate a sequence and a related key expression into a dictionary.

' 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 products As DataTable = ds.Tables("Product")

Dim scoreRecordsDict = products.AsEnumerable(). _
    ToDictionary(Function(record) record.Field(Of String)("Name"))

Console.WriteLine("Top Tube's ProductID: {0}", _
    scoreRecordsDict("Top Tube")("ProductID"))

// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);

DataTable products = ds.Tables["Product"];


var scoreRecordsDict = products.AsEnumerable().
    ToDictionary(record => record.Field<string>("Name"));
Console.WriteLine("Top Tube's ProductID: {0}",
    scoreRecordsDict["Top Tube"]["ProductID"]);

ToList

Example

This example uses the ToList<TSource> method to immediately evaluate a sequence into a List<T>, where T is of type DataRow.

' 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 products As DataTable = ds.Tables("Product")

Dim productList = products.AsEnumerable().ToList()

Dim query = _
    From product In productList _
    Select product _
    Order By product.Field(Of String)("Name")

Console.WriteLine("The sorted name list:")

For Each product In query
    Console.WriteLine(product.Field(Of String)("Name").ToLower(CultureInfo.InvariantCulture))
Next

// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);

DataTable products = ds.Tables["Product"];

IEnumerable<DataRow> productList = products.AsEnumerable().ToList();

IEnumerable<DataRow> query =
    from product in productList
    orderby product.Field<string>("Name")
    select product;

Console.WriteLine("The product list, ordered by product name:");
foreach (DataRow product in query)
{
    Console.WriteLine(product.Field<string>("Name").ToLower(CultureInfo.InvariantCulture));
}

See Also

Concepts

Loading Data Into a DataSet

Standard Query Operators Overview

Other Resources

LINQ to DataSet Examples