Method-Based voorbeelden van querysyntaxis: Aggregate Operators (LINQ to DataSet)

Artikel
04/02/2025

De voorbeelden in dit onderwerp laten zien hoe de Aggregate, Average, Count, LongCount, Max, Min en Sum operators worden gebruikt om een query uit te voeren op een DataSet en gegevens te aggregeren met behulp van de methode-queriesyntaxis.

De FillDataSet methode die in deze voorbeelden wordt gebruikt, wordt opgegeven in Gegevens laden in een DataSet-.

In de voorbeelden in dit onderwerp worden de tabellen Contact, Adres, Product, SalesOrderHeader en SalesOrderDetail gebruikt in de voorbeelddatabase AdventureWorks.

In de voorbeelden in dit onderwerp worden de volgende using/Imports verklaringen gebruikt:

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

Voor meer informatie, zie Hoe te: Een LINQ naar DataSet-project maken in Visual Studio:.

Samenvoegen

Voorbeeld

In dit voorbeeld wordt de methode #D0 gebruikt om de eerste vijf contactpersonen op te halen uit de #D1 tabel en een door komma's gescheiden lijst met de achternamen te maken.

// 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)

Gemiddeld

Voorbeeld

In dit voorbeeld wordt de Average-methode gebruikt om de gemiddelde lijstprijs van de producten te vinden.

// 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 ${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)

Voorbeeld

In dit voorbeeld wordt de Average-methode gebruikt om de gemiddelde lijstprijs van de producten van elke stijl te vinden.

// 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: {product.Style} Average list price: {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

Voorbeeld

In dit voorbeeld wordt de methode Average gebruikt om het gemiddelde verschuldigde bedrag te vinden.

// 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 {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)

Voorbeeld

In dit voorbeeld wordt de Average methode gebruikt om het gemiddelde totaal te berekenen voor elke contact-ID.

// 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 = {order.Category} \t Average TotalDue = {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

Voorbeeld

In dit voorbeeld wordt de Average methode gebruikt om orders op te halen met gemiddelde TotalDue voor elke contactpersoon.

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

Aantal

Voorbeeld

In dit voorbeeld wordt de methode #D0 gebruikt om het aantal producten in de tabel #D1 te retourneren.

// 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 {numProducts} products.");

' 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.")

Voorbeeld

In dit voorbeeld wordt de Count-methode gebruikt om een lijst met contact-id's te retourneren en het aantal bestellingen dat elk heeft.

// 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 = {contact.CustomerID} \t OrderCount = {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

Voorbeeld

In dit voorbeeld worden producten gegroepeerd op kleur en wordt de Count-methode gebruikt om het aantal producten in elke kleurgroep te retourneren.

// 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 = {product.Color} \t ProductCount = {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

Voorbeeld

In dit voorbeeld wordt het aantal contactpersonen als een lang geheel getal geteld.

// 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 {numberOfContacts} Contacts");

' 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

Voorbeeld

In dit voorbeeld wordt de Max-methode gebruikt om het grootste verschuldigde totaal op te halen.

// 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 {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)

Voorbeeld

In dit voorbeeld wordt de Max methode gebruikt om het grootste totaal op te halen voor elke contact-ID.

// 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 = {order.Category} \t Maximum TotalDue = {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

Voorbeeld

In dit voorbeeld wordt de Max methode gebruikt om de orders op te halen met de grootste TotalDue voor elke contactpersoon-id.

// 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($"ContactID: {orderGroup.Category}");
    foreach (var order in orderGroup.CheapestProducts)
    {
        Console.WriteLine($"MaxTotalDue {order.Field<decimal>("TotalDue")} for SalesOrderID {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

Minuut

Voorbeeld

In dit voorbeeld wordt de Min methode gebruikt om het kleinste verschuldigde totaal op te halen.

// 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 {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)

Voorbeeld

In dit voorbeeld wordt de methode #D0 gebruikt om het kleinste totaalbedrag op te halen voor elke contact-ID.

// 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 = {order.Category} \t Minimum TotalDue = {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

Voorbeeld

In dit voorbeeld wordt de Min-methode gebruikt om de orders op te halen met het kleinste verschuldigde totaal voor elke contactpersoon.

// 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($"ContactID: {orderGroup.Category}");
    foreach (var order in orderGroup.smallestTotalDue)
    {
        Console.WriteLine($"Minimum TotalDue {order.Field<decimal>("TotalDue")} for SalesOrderID {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

Som

Voorbeeld

In dit voorbeeld wordt de methode #D0 gebruikt om het totale aantal orderhoeveelheden in de tabel #D1 op te halen.

// 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 {totalOrderQty} OrderQty.");

Voorbeeld

In dit voorbeeld wordt de Sum methode gebruikt om het totale verschuldigde bedrag voor elke contact ID op te halen.

// 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 = {order.Category} \t TotalDue sum = {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

Zie ook

Gegevens laden in een DataSet
LINQ-voorbeelden met DataSet
Overzicht van Standard-queryoperators (C#)
Visual Basic: Overzicht van standaardquery-operators

Delen via

Method-Based voorbeelden van querysyntaxis: Aggregate Operators (LINQ to DataSet)

Samenvoegen

Voorbeeld

Gemiddeld

Voorbeeld

Voorbeeld

Voorbeeld

Voorbeeld

Voorbeeld

Aantal

Voorbeeld

Voorbeeld

Voorbeeld

LongCount

Voorbeeld

Max

Voorbeeld

Voorbeeld

Voorbeeld

Minuut

Voorbeeld

Voorbeeld

Voorbeeld

Som

Voorbeeld

Voorbeeld

Zie ook

Aanvullende resources