メソッド ベースのクエリ構文例:集合演算子 (LINQ to DataSet)

このトピックの例では、Distinct、Except、Intersect、Union の各演算子を使用して、データ行の集合に対して値ベースの比較操作を実行する方法を示します。DataSet へのデータの読み込み。DataRowComparer について詳しくは、「DataRow の比較」をご覧ください。

これらの例で使用されている FillDataSet メソッドは、「DataSet へのデータの読み込み」で指定されています。

このトピックの例には、AdventureWorks サンプル データベースの Contact、Address、Product、SalesOrderHeader、SalesOrderDetail の各テーブルが使用されています。

このトピックの例には、次の using/Imports ステートメントが使用されています。

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Globalization;
using System.Linq;
using System.Windows.Forms;

Option Explicit On

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

詳細については、Visual Studio で LINQ to DataSet プロジェクトを作成する」を参照してください。

Distinct

例

この例では、Distinct メソッドを使用してシーケンス内の重複する要素を削除します。

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

List<DataRow> rows = new List<DataRow>();

DataTable contact = ds.Tables["Contact"];

// Get 100 rows from the Contact table.
IEnumerable<DataRow> query = (from c in contact.AsEnumerable()
                              select c).Take(100);

DataTable contactsTableWith100Rows = query.CopyToDataTable();

// Add 100 rows to the list.
foreach (DataRow row in contactsTableWith100Rows.Rows)
    rows.Add(row);

// Create duplicate rows by adding the same 100 rows to the list.
foreach (DataRow row in contactsTableWith100Rows.Rows)
    rows.Add(row);

DataTable table =
    System.Data.DataTableExtensions.CopyToDataTable<DataRow>(rows);

// Find the unique contacts in the table.
IEnumerable<DataRow> uniqueContacts =
    table.AsEnumerable().Distinct(DataRowComparer.Default);

Console.WriteLine("Unique contacts:");
foreach (DataRow uniqueContact in uniqueContacts)
{
    Console.WriteLine(uniqueContact.Field<Int32>("ContactID"));
}

' 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 rows As List(Of DataRow) = New List(Of DataRow)

Dim contacts As DataTable = ds.Tables("Contact")

' Get 100 rows from the Contact table.
Dim query = ( _
    From c In contacts.AsEnumerable() _
    Select c).Take(100)

Dim contactsTableWith100Rows = query.CopyToDataTable()

' Add 100 rows to the list.
For Each row In contactsTableWith100Rows.Rows
    rows.Add(row)
Next

' Create duplicate rows by adding the same 100 rows to the list.
For Each row In contactsTableWith100Rows.Rows
    rows.Add(row)
Next

Dim table = _
        System.Data.DataTableExtensions.CopyToDataTable(Of DataRow)(rows)

' Find the unique contacts in the table.
Dim uniqueContacts = _
    table.AsEnumerable().Distinct(DataRowComparer.Default)

Console.WriteLine("Unique contacts:")
For Each uniqueContact In uniqueContacts
    Console.WriteLine(uniqueContact.Field(Of Integer)("ContactID"))
Next

除く

例

この例では、最初のテーブルにのみ存在し、かつ 2 つ目のテーブルには存在しない連絡先だけを、Except メソッドを使用して取得します。

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

DataTable contactTable = ds.Tables["Contact"];

// Create two tables.
IEnumerable<DataRow> query1 = from contact in contactTable.AsEnumerable()
                              where contact.Field<string>("Title") == "Ms."
                              select contact;

IEnumerable<DataRow> query2 = from contact in contactTable.AsEnumerable()
                              where contact.Field<string>("FirstName") == "Sandra"
                              select contact;

DataTable contacts1 = query1.CopyToDataTable();
DataTable contacts2 = query2.CopyToDataTable();

// Find the contacts that are in the first
// table but not the second.
var contacts = contacts1.AsEnumerable().Except(contacts2.AsEnumerable(),
                                               DataRowComparer.Default);

Console.WriteLine("Except of employees tables");
foreach (DataRow row in contacts)
{
    Console.WriteLine("Id: {0} {1} {2} {3}",
        row["ContactID"], row["Title"], row["FirstName"], row["LastName"]);
}

' 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 contactTable As DataTable = ds.Tables("Contact")

Dim query1 = _
    From contact In contactTable.AsEnumerable() _
    Where contact.Field(Of String)("Title") = "Ms." _
    Select contact

Dim query2 = _
    From contact In contactTable.AsEnumerable() _
    Where contact.Field(Of String)("FirstName") = "Sandra" _
    Select contact

Dim contacts1 = query1.CopyToDataTable()
Dim contacts2 = query2.CopyToDataTable()

' Find the contacts that are in the first
' table but not the second.
Dim contacts = contacts1.AsEnumerable().Except(contacts2.AsEnumerable(), _
                                              DataRowComparer.Default)

Console.WriteLine("Except of employees tables")

For Each row In contacts
    Console.WriteLine("Id: {0} {1} {2} {3}", _
            row("ContactID"), row("Title"), row("FirstName"), row("LastName"))
Next

交差

例

この例では、両方のテーブルに存在する連絡先を Intersect メソッドを使用して取得します。

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

DataTable contactTable = ds.Tables["Contact"];

// Create two tables.
IEnumerable<DataRow> query1 = from contact in contactTable.AsEnumerable()
                              where contact.Field<string>("Title") == "Ms."
                              select contact;

IEnumerable<DataRow> query2 = from contact in contactTable.AsEnumerable()
                              where contact.Field<string>("FirstName") == "Sandra"
                              select contact;

DataTable contacts1 = query1.CopyToDataTable();
DataTable contacts2 = query2.CopyToDataTable();

// Find the intersection of the two tables.
var contacts = contacts1.AsEnumerable().Intersect(contacts2.AsEnumerable(),
                                                    DataRowComparer.Default);

Console.WriteLine("Intersection of contacts tables");
foreach (DataRow row in contacts)
{
    Console.WriteLine("Id: {0} {1} {2} {3}",
        row["ContactID"], row["Title"], row["FirstName"], row["LastName"]);
}

' 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 contactTable As DataTable = ds.Tables("Contact")

Dim query1 = _
    From contact In contactTable.AsEnumerable() _
    Where contact.Field(Of String)("Title") = "Ms." _
    Select contact

Dim query2 = _
    From contact In contactTable.AsEnumerable() _
    Where contact.Field(Of String)("FirstName") = "Sandra" _
    Select contact

Dim contacts1 = query1.CopyToDataTable()
Dim contacts2 = query2.CopyToDataTable()

Dim contacts = contacts1.AsEnumerable() _
    .Intersect(contacts2.AsEnumerable(), DataRowComparer.Default)

Console.WriteLine("Intersect of employees tables")

For Each row In contacts
    Console.WriteLine("Id: {0} {1} {2} {3}", _
            row("ContactID"), row("Title"), row("FirstName"), row("LastName"))
Next

和集合

例

この例では、Union メソッドを使用して、2 つのテーブルのいずれかから一意の連絡先を取得します。

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

// Create two tables.
DataTable contactTable = ds.Tables["Contact"];
IEnumerable<DataRow> query1 = from contact in contactTable.AsEnumerable()
                              where contact.Field<string>("Title") == "Ms."
                              select contact;

IEnumerable<DataRow> query2 = from contact in contactTable.AsEnumerable()
                              where contact.Field<string>("FirstName") == "Sandra"
                              select contact;

DataTable contacts1 = query1.CopyToDataTable();
DataTable contacts2 = query2.CopyToDataTable();

// Find the union of the two tables.
var contacts = contacts1.AsEnumerable().Union(contacts2.AsEnumerable(),
                                                DataRowComparer.Default);

Console.WriteLine("Union of contacts tables:");
foreach (DataRow row in contacts)
{
    Console.WriteLine("Id: {0} {1} {2} {3}",
        row["ContactID"], row["Title"], row["FirstName"], row["LastName"]);
}

' 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 contactTable As DataTable = ds.Tables("Contact")

Dim query1 = _
    From contact In contactTable.AsEnumerable() _
    Where contact.Field(Of String)("Title") = "Ms." _
    Select contact

Dim query2 = _
    From contact In contactTable.AsEnumerable() _
    Where contact.Field(Of String)("FirstName") = "Sandra" _
    Select contact

Dim contacts1 = query1.CopyToDataTable()
Dim contacts2 = query2.CopyToDataTable()

Dim contacts = contacts1.AsEnumerable().Union(contacts2.AsEnumerable(), _
                                              DataRowComparer.Default)

Console.WriteLine("Union of employees tables")
For Each row In contacts
    Console.WriteLine("Id: {0} {1} {2} {3}", _
            row("ContactID"), row("Title"), row("FirstName"), row("LastName"))
Next

関連項目

• DataSet へのデータの読み込み
• LINQ to DataSet の例
• 標準クエリ演算子の概要 (C#)
• 標準クエリ演算子の概要 (Visual Basic)