Exemples de syntaxe d'expression de requête : opérateurs d'agrégation (LINQ to DataSet)
Article
Les exemples de cette rubrique montrent comment utiliser les méthodes Average, Count, Max, Min et Sum pour interroger un DataSet et agréger les données à l'aide de la syntaxe d'expression de requête.
Les exemples de cette rubrique utilisent les tables Contact, Address, Product, SalesOrderHeader et SalesOrderDetail de l'exemple de base de données AdventureWorks.
Les exemples de cette rubrique utilisent les instructions using/Imports suivantes :
C#
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Globalization;
using System.Linq;
using System.Windows.Forms;
Cet exemple utilise la méthode Average pour trouver le prix moyen courant des produits de chaque style.
C#
// 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
selectnew
{
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
Exemple
Cet exemple utilise Average pour obtenir le montant total moyen dû de chaque ID de contact.
C#
// 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
selectnew
{
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
Exemple
Cet exemple utilise Average pour obtenir les commandes avec la moyenne de TotalDue pour chaque contact.
C#
// 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"))
selectnew
{
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
Count
Exemple
Cet exemple utilise Count pour retourner une liste d'ID de contact et le nombre de commandes de chaque ID de contact.
C#
// 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()
selectnew
{
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
Exemple
Cet exemple regroupe les produits par couleur et utilise Count pour retourner le nombre de produits dans chaque groupe de couleur.
C#
// 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
selectnew { 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
Max
Exemple
Cet exemple utilise la méthode Max pour obtenir le montant total dû le plus élevé pour chaque ID de contact.
C#
// 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
selectnew
{
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
Exemple
Cet exemple utilise la méthode Max pour obtenir les commandes présentant le TotalDue le plus élevé pour chaque ID de contact.
C#
// 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"))
selectnew
{
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
Exemple
Cet exemple utilise la méthode Min pour obtenir le montant total dû le plus bas pour chaque ID de contact.
C#
// 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
selectnew
{
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
Exemple
Cet exemple utilise la méthode Min pour obtenir les commandes présentant le montant total dû le plus bas pour chaque ID de contact.
C#
// 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"))
selectnew
{
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
Exemple
Cet exemple utilise la méthode Sum pour obtenir le montant total dû de chaque ID de contact.
C#
// 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
selectnew
{
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
Apprenez à écrire des requêtes avancées dans le langage de requête Kusto (KQL) en utilisant les fonctions d’agrégation, l’opérateur render et des variables.