Beispiele für die methodenbasierte Abfragesyntax: Aggregierungsoperatoren (LINQ to DataSet)

Artikel
08/21/2008

Aktualisiert: November 2007

In den Beispielen in diesem Thema wird gezeigt, wie Sie mithilfe der Operatoren Aggregate, Average, Count, LongCount, Max, Min und Sum und der methodenbasierten Abfragesyntax ein DataSet abfragen und Daten aggregieren können.

Informationen zur FillDataSet-Methode, die in diesen Beispielen verwendet wird, finden Sie unter Laden von Daten in ein 'DataSet'.

In den Beispielen in diesem Thema wird auf die Tabellen Contact, Address, Product, SalesOrderHeader und SalesOrderDetail in der AdventureWorks-Beispieldatenbank zurückgegriffen.

Die Beispiele in diesem Thema beziehen sich auf die folgenden using/Imports-Anweisungen:

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;

Weitere Informationen dazu finden Sie unter Gewusst wie: Erstellen eines LINQ to DataSet-Projekts in Visual Studio.

Aggregate

Beispiel

In diesem Beispiel wird die Aggregate-Methode verwendet, um die ersten 5 Kontakte aus der Contact-Tabelle abzurufen und eine Liste der Nachnamen zu erstellen, in der die einzelnen Einträge durch Kommas voneinander getrennt sind.

' 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 IEnumerable(Of DataRow) = _
    ds.Tables("Contact").AsEnumerable()

Dim nameList As String = _
        contacts.Take(5).Select(Function(contact) contact.Field(Of String)("LastName")). _
            Aggregate(Function(workingList, next1) workingList + "," + next1)

Console.WriteLine(nameList)

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

IEnumerable<DataRow> contacts = ds.Tables["Contact"].AsEnumerable();

string nameList =
    contacts.Take(5).Select(contact => contact.Field<string>("LastName")).Aggregate((workingList, next) => workingList + "," + next);

Console.WriteLine(nameList);

Average

Beispiel

In diesem Beispiel wird die Average-Methode verwendet, um den durchschnittlichen Listenpreis der Produkte zu ermitteln.

' 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 IEnumerable(Of DataRow) = _
    ds.Tables("Product").AsEnumerable()

Dim averageListPrice As Decimal = _
    products.Average(Function(product) product. _
            Field(Of Decimal)("ListPrice"))

Console.WriteLine("The average list price of all the products is $" & _
    averageListPrice)

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

var products = ds.Tables["Product"].AsEnumerable();

Decimal averageListPrice =
    products.Average(product => product.Field<Decimal>("ListPrice"));

Console.WriteLine("The average list price of all the products is ${0}",
    averageListPrice);

Beispiel

In diesem Beispiel wird die Average-Methode verwendet, um den durchschnittlichen Listenpreis der Produkte für die einzelnen Stile zu ermitteln.

' 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 IEnumerable(Of DataRow) = _
    ds.Tables("Product").AsEnumerable()

Dim query = _
    From product In products _
    Group product By style = product.Field(Of String)("Style") Into g = Group _
    Select New With _
        { _
            .Style = style, _
            .AverageListPrice = g.Average(Function(product) _
                    product.Field(Of Decimal)("ListPrice")) _
        }

For Each product In query
    Console.WriteLine("Product style: {0} Average list price: {1}", _
        product.Style, product.AverageListPrice)
Next

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

var products = ds.Tables["Product"].AsEnumerable();

var query = from product in products
            group product by product.Field<string>("Style") into g
            select new
            {
                Style = g.Key,
                AverageListPrice =
                    g.Average(product => product.Field<Decimal>("ListPrice"))
            };

foreach (var product in query)
{
    Console.WriteLine("Product style: {0} Average list price: {1}",
        product.Style, product.AverageListPrice);
}

Beispiel

In diesem Beispiel wird die Average-Methode verwendet, um den durchschnittlichen fälligen Gesamtbetrag zu ermitteln.

' 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 orders As DataTable = ds.Tables("SalesOrderHeader")

Dim averageTotalDue As Decimal = orders.AsEnumerable(). _
    Average(Function(order) order.Field(Of Decimal)("TotalDue"))
Console.WriteLine("The average TotalDue is {0}.", _
    averageTotalDue)

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

DataTable orders = ds.Tables["SalesOrderHeader"];

Decimal averageTotalDue = orders.AsEnumerable().
    Average(order => order.Field<decimal>("TotalDue"));
Console.WriteLine("The average TotalDue is {0}.",
    averageTotalDue);

Beispiel

In diesem Beispiel wird die Average-Methode verwendet, um für jede Kontakt-ID den durchschnittlichen fälligen Gesamtbetrag zu ermitteln.

' 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 orders As DataTable = ds.Tables("SalesOrderHeader")

Dim query = _
    From order In orders.AsEnumerable() _
    Group order By contactID = order.Field(Of Int32)("ContactID") Into g = Group _
    Select New With _
    { _
        .Category = contactID, _
        .averageTotalDue = g.Average(Function(order) order. _
                Field(Of Decimal)("TotalDue")) _
    }

For Each order In query
    Console.WriteLine("ContactID = {0} " & vbTab & _
        " Average TotalDue = {1}", order.Category, _
        order.averageTotalDue)
Next

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

DataTable orders = ds.Tables["SalesOrderHeader"];

var query =
    from order in orders.AsEnumerable()
    group order by order.Field<Int32>("ContactID") into g
    select new
    {
        Category = g.Key,
        averageTotalDue =
            g.Average(order => order.Field<decimal>("TotalDue"))
    };

foreach (var order in query)
{
    Console.WriteLine("ContactID = {0} \t Average TotalDue = {1}",
        order.Category,
        order.averageTotalDue);
}

Beispiel

In diesem Beispiel wird die Average-Methode verwendet, um die Aufträge mit dem durchschnittlichen TotalDue-Wert für jeden Kontakt abzurufen.

' 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 orders As DataTable = ds.Tables("SalesOrderHeader")

Dim query = _
    From order In orders.AsEnumerable() _
    Group order By contactID = order.Field(Of Int32)("ContactID") Into g = Group _
    Let averageTotalDue = g.Average(Function(order) order.Field(Of Decimal)("TotalDue")) _
    Select New With _
    { _
        .Category = contactID, _
        .CheapestProducts = g.Where(Function(order) order. _
                Field(Of Decimal)("TotalDue") = averageTotalDue) _
    }

For Each orderGroup In query
    Console.WriteLine("ContactID: " & orderGroup.Category)
    For Each order In orderGroup.CheapestProducts
        Console.WriteLine("Average total due for SalesOrderID {1} is: {0}", _
            order.Field(Of Decimal)("TotalDue"), _
            order.Field(Of Int32)("SalesOrderID"))
    Next
    Console.WriteLine("")
Next

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

DataTable orders = ds.Tables["SalesOrderHeader"];

var query =
    from order in orders.AsEnumerable()
    group order by order.Field<Int32>("ContactID") into g
    let averageTotalDue = g.Average(order => order.Field<decimal>("TotalDue"))
    select new
    {
        Category = g.Key,
        CheapestProducts =
            g.Where(order => order.Field<decimal>("TotalDue") ==
                        averageTotalDue)
    };


foreach (var orderGroup in query)
{
    Console.WriteLine("ContactID: {0}", orderGroup.Category);
    foreach (var order in orderGroup.CheapestProducts)
    {
        Console.WriteLine("Average total due for SalesOrderID {1} is: {0}",
            order.Field<decimal>("TotalDue"),
            order.Field<Int32>("SalesOrderID"));
    }
    Console.WriteLine("");
}

Count

Beispiel

In diesem Beispiel wird die Count-Methode verwendet, um die Anzahl der Produkte in der Product-Tabelle zu ermitteln.

' 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 numProducts = products.AsEnumerable().Count()

Console.WriteLine("There are " & numProducts & " products.")

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

var products = ds.Tables["Product"].AsEnumerable();

int numProducts = products.Count();

Console.WriteLine("There are {0} products.", numProducts);

Beispiel

In diesem Beispiel wird die Count-Methode verwendet, um eine Liste der Kontakt-IDs und der jeweiligen Anzahl von Aufträgen zu erstellen.

' 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() _
    Select New With _
    { _
        .ContactID = contact.Field(Of Integer)("ContactID"), _
        .OrderCount = contact.GetChildRows("SalesOrderContact").Count() _
    }

For Each contact In query
    Console.Write("CustomerID = " & contact.ContactID)
    Console.WriteLine(vbTab & "OrderCount = " & contact.OrderCount)
Next

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

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

var query = from contact in contacts.AsEnumerable()
            select new
            {
                CustomerID = contact.Field<int>("ContactID"),
                OrderCount =
                    contact.GetChildRows("SalesOrderContact").Count()
            };

foreach (var contact in query)
{
    Console.WriteLine("CustomerID = {0} \t OrderCount = {1}",
        contact.CustomerID,
        contact.OrderCount);
}

Beispiel

In diesem Beispiel werden die Produkte nach ihrer Farbe gruppiert. Anschließend wird die Count-Methode verwendet, um die Anzahl der Produkte in jeder Farbgruppe abzurufen.

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 query = _
    From product In products.AsEnumerable() _
    Group product By color = product.Field(Of String)("Color") Into g = Group _
    Select New With {.Color = color, .ProductCount = g.Count()}

For Each product In query
    Console.WriteLine("Color = {0} " & vbTab & "ProductCount = {1}", _
        product.Color, _
        product.ProductCount)
Next

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

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

var query =
    from product in products.AsEnumerable()
    group product by product.Field<string>("Color") into g
    select new { Color = g.Key, ProductCount = g.Count() };

foreach (var product in query)
{
    Console.WriteLine("Color = {0} \t ProductCount = {1}",
        product.Color,
        product.ProductCount);
}

LongCount

Beispiel

In diesem Beispiel wird die Anzahl der Kontakte als lange ganze Zahl abgerufen.

' 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 numberOfContacts = contacts.AsEnumerable().LongCount()

Console.WriteLine("There are {0} Contacts", numberOfContacts)

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


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

long numberOfContacts = contacts.AsEnumerable().LongCount();
Console.WriteLine("There are {0} Contacts", numberOfContacts);

Max

Beispiel

In diesem Beispiel wird die Max-Methode verwendet, um den größten fälligen Gesamtbetrag zu ermitteln.

' 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 orders As DataTable = ds.Tables("SalesOrderHeader")

Dim maxTotalDue As Decimal = orders.AsEnumerable(). _
    Max(Function(w) w.Field(Of Decimal)("TotalDue"))
Console.WriteLine("The maximum TotalDue is {0}.", maxTotalDue)

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

DataTable orders = ds.Tables["SalesOrderHeader"];

Decimal maxTotalDue = orders.AsEnumerable().
    Max(w => w.Field<decimal>("TotalDue"));
Console.WriteLine("The maximum TotalDue is {0}.",
    maxTotalDue);

Beispiel

In diesem Beispiel wird die Max-Methode verwendet, um für jede Kontakt-ID den größten fälligen Gesamtbetrag zu ermitteln.

' 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 orders As DataTable = ds.Tables("SalesOrderHeader")

Dim query = _
   From order In orders.AsEnumerable() _
   Group order By contactID = order.Field(Of Int32)("ContactID") Into g = Group _
   Select New With _
   { _
       .Category = contactID, _
       .maxTotalDue = _
           g.Max(Function(order) order.Field(Of Decimal)("TotalDue")) _
   }
For Each order In query
    Console.WriteLine("ContactID = {0} " & vbTab & _
        " Maximum TotalDue = {1}", _
        order.Category, order.maxTotalDue)
Next

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

DataTable orders = ds.Tables["SalesOrderHeader"];

var query =
    from order in orders.AsEnumerable()
    group order by order.Field<Int32>("ContactID") into g
    select new
    {
        Category = g.Key,
        maxTotalDue =
            g.Max(order => order.Field<decimal>("TotalDue"))
    };

foreach (var order in query)
{
    Console.WriteLine("ContactID = {0} \t Maximum TotalDue = {1}",
        order.Category, order.maxTotalDue);
}

Beispiel

In diesem Beispiel wird die Max-Methode verwendet, um für jede Kontakt-ID die Aufträge mit dem größten TotalDue-Wert abzurufen.

' 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 orders As DataTable = ds.Tables("SalesOrderHeader")

Dim query = _
    From order In orders.AsEnumerable() _
    Group order By contactID = order.Field(Of Int32)("ContactID") Into g = Group _
    Let maxTotalDue = g.Max(Function(order) order.Field(Of Decimal)("TotalDue")) _
    Select New With _
    { _
        .Category = contactID, _
        .CheapestProducts = _
            g.Where(Function(order) order. _
                    Field(Of Decimal)("TotalDue") = maxTotalDue) _
    }

For Each orderGroup In query
    Console.WriteLine("ContactID: " & orderGroup.Category)
    For Each order In orderGroup.CheapestProducts
        Console.WriteLine("MaxTotalDue {0} for SalesOrderID {1} ", _
            order.Field(Of Decimal)("TotalDue"), _
            order.Field(Of Int32)("SalesOrderID"))
    Next
Next

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

DataTable orders = ds.Tables["SalesOrderHeader"];

var query =
    from order in orders.AsEnumerable()
    group order by order.Field<Int32>("ContactID") into g
    let maxTotalDue = g.Max(order => order.Field<decimal>("TotalDue"))
    select new
    {
        Category = g.Key,
        CheapestProducts =
            g.Where(order => order.Field<decimal>("TotalDue") ==
                        maxTotalDue)
    };


foreach (var orderGroup in query)
{
    Console.WriteLine("ContactID: {0}", orderGroup.Category);
    foreach (var order in orderGroup.CheapestProducts)
    {
        Console.WriteLine("MaxTotalDue {0} for SalesOrderID {1}: ",
            order.Field<decimal>("TotalDue"),
            order.Field<Int32>("SalesOrderID"));
    }
}

Min

Beispiel

In diesem Beispiel wird die Min-Methode verwendet, um den kleinsten fälligen Gesamtbetrag zu ermitteln.

' 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 orders As DataTable = ds.Tables("SalesOrderHeader")

Dim smallestTotalDue As Decimal = orders.AsEnumerable(). _
    Min(Function(totalDue) totalDue.Field(Of Decimal)("TotalDue"))

Console.WriteLine("The smallest TotalDue is {0}.", smallestTotalDue)

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

DataTable orders = ds.Tables["SalesOrderHeader"];

Decimal smallestTotalDue = orders.AsEnumerable().
    Min(totalDue => totalDue.Field<decimal>("TotalDue"));
Console.WriteLine("The smallest TotalDue is {0}.",
    smallestTotalDue);

Beispiel

In diesem Beispiel wird die Min-Methode verwendet, um für jede Kontakt-ID den kleinsten fälligen Gesamtbetrag zu ermitteln.

' 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 orders As DataTable = ds.Tables("SalesOrderHeader")

Dim query = _
    From order In orders.AsEnumerable() _
    Group order By contactID = order.Field(Of Int32)("ContactID") Into g = Group _
    Select New With _
    { _
       .Category = contactID, _
       .smallestTotalDue = g.Min(Function(order) _
                order.Field(Of Decimal)("TotalDue")) _
    }

For Each order In query
    Console.WriteLine("ContactID = {0} " & vbTab & _
        "Minimum TotalDue = {1}", order.Category, order.smallestTotalDue)
Next

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

DataTable orders = ds.Tables["SalesOrderHeader"];

var query =
    from order in orders.AsEnumerable()
    group order by order.Field<Int32>("ContactID") into g
    select new
    {
        Category = g.Key,
        smallestTotalDue =
            g.Min(order => order.Field<decimal>("TotalDue"))
    };

foreach (var order in query)
{
    Console.WriteLine("ContactID = {0} \t Minimum TotalDue = {1}",
        order.Category, order.smallestTotalDue);
}

Beispiel

In diesem Beispiel wird die Min-Methode verwendet, um für jeden Kontakt die Aufträge mit dem kleinsten fälligen Gesamtbetrag zu ermitteln.

' 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 orders As DataTable = ds.Tables("SalesOrderHeader")

Dim query = _
    From order In orders.AsEnumerable() _
    Group order By contactID = order.Field(Of Int32)("ContactID") Into g = Group _
    Let minTotalDue = g.Min(Function(order) order.Field(Of Decimal)("TotalDue")) _
    Select New With _
    { _
       .Category = contactID, _
       .smallestTotalDue = g.Where(Function(order) order. _
            Field(Of Decimal)("TotalDue") = minTotalDue) _
    }

For Each orderGroup In query
    Console.WriteLine("ContactID: " & orderGroup.Category)
    For Each order In orderGroup.smallestTotalDue
        Console.WriteLine("Mininum TotalDue {0} for SalesOrderID {1} ", _
            order.Field(Of Decimal)("TotalDue"), _
            order.Field(Of Int32)("SalesOrderID"))
    Next
    Console.WriteLine("")
Next

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

DataTable orders = ds.Tables["SalesOrderHeader"];

var query =
    from order in orders.AsEnumerable()
    group order by order.Field<Int32>("ContactID") into g
    let minTotalDue = g.Min(order => order.Field<decimal>("TotalDue"))
    select new
    {
        Category = g.Key,
        smallestTotalDue =
            g.Where(order => order.Field<decimal>("TotalDue") ==
                        minTotalDue)
    };


foreach (var orderGroup in query)
{
    Console.WriteLine("ContactID: {0}", orderGroup.Category);
    foreach (var order in orderGroup.smallestTotalDue)
    {
        Console.WriteLine("Mininum TotalDue {0} for SalesOrderID {1}: ",
            order.Field<decimal>("TotalDue"),
            order.Field<Int32>("SalesOrderID"));
    }
    Console.WriteLine("");
}

Sum

Beispiel

In diesem Beispiel wird die Sum-Methode verwendet, um die Gesamtzahl der Bestellmengen in der SalesOrderDetail-Tabelle abzurufen.

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


DataTable orders = ds.Tables["SalesOrderDetail"];

double totalOrderQty = orders.AsEnumerable().
    Sum(o => o.Field<Int16>("OrderQty"));
Console.WriteLine("There are a total of {0} OrderQty.",
    totalOrderQty);

Beispiel

In diesem Beispiel wird die Sum-Methode verwendet, um für jede Kontakt-ID den fälligen Gesamtbetrag zu ermitteln.

' 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 orders As DataTable = ds.Tables("SalesOrderHeader")

Dim query = _
    From order In orders.AsEnumerable() _
    Group order By contactID = order.Field(Of Int32)("ContactID") Into g = Group _
    Select New With _
       { _
           .Category = contactID, _
           .TotalDue = g.Sum(Function(order) order. _
                Field(Of Decimal)("TotalDue")) _
       }

For Each order In query
    Console.WriteLine("ContactID = {0} " & vbTab & "TotalDue sum = {1}", _
        order.Category, order.TotalDue)
Next

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

DataTable orders = ds.Tables["SalesOrderHeader"];

var query =
    from order in orders.AsEnumerable()
    group order by order.Field<Int32>("ContactID") into g
    select new
    {
        Category = g.Key,
        TotalDue = g.Sum(order => order.Field<decimal>("TotalDue")),
    };
foreach (var order in query)
{
    Console.WriteLine("ContactID = {0} \t TotalDue sum = {1}",
        order.Category, order.TotalDue);
}

Siehe auch

Konzepte

Laden von Daten in ein 'DataSet'

Übersicht über Standardabfrageoperatoren

Weitere Ressourcen

LINQ to DataSet-Beispiele

Freigeben über

Beispiele für die methodenbasierte Abfragesyntax: Aggregierungsoperatoren (LINQ to DataSet)

Aggregate

Beispiel

Average

Beispiel

Beispiel

Beispiel

Beispiel

Beispiel

Count

Beispiel

Beispiel

Beispiel

LongCount

Beispiel

Max

Beispiel

Beispiel

Beispiel

Min

Beispiel

Beispiel

Beispiel

Sum

Beispiel

Beispiel

Siehe auch

Konzepte

Weitere Ressourcen

Zusätzliche Ressourcen