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

Artikel
04/06/2023

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.

Die in diesen Beispielen verwendete FillDataSet-Methode wird unter Laden von Daten in ein DataSet beschrieben.

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

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

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

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

Aggregat

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.
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);

' 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)

Average

Beispiel

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

// 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);

' 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)

Beispiel

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

// 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);
}

' 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

Beispiel

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

// 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);

' 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)

Beispiel

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

// 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);
}

' 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

Beispiel

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

// 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("");
}

' 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

Anzahl

Beispiel

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

// 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);

' 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.")

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.
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);
}

' 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

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.

// 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);
}

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

LongCount

Beispiel

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

// 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);

' 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)

Max

Beispiel

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

// 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);

' 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)

Beispiel

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

// 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);
}

' 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

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.
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"));
    }
}

' 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

Min

Beispiel

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

// 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);

' 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)

Beispiel

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

// 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);
}

' 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

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.
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("Minimum TotalDue {0} for SalesOrderID {1}: ",
            order.Field<decimal>("TotalDue"),
            order.Field<Int32>("SalesOrderID"));
    }
    Console.WriteLine("");
}

' 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("Minimum TotalDue {0} for SalesOrderID {1} ", _
            order.Field(Of Decimal)("TotalDue"), _
            order.Field(Of Int32)("SalesOrderID"))
    Next
    Console.WriteLine("")
Next

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.
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);
}

' 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

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

Aggregat

Beispiel

Average

Beispiel

Beispiel

Beispiel

Beispiel

Beispiel

Anzahl

Beispiel

Beispiel

Beispiel

LongCount

Beispiel

Max

Beispiel

Beispiel

Beispiel

Min

Beispiel

Beispiel

Beispiel

Sum

Beispiel

Beispiel

Siehe auch

Zusätzliche Ressourcen