Exemplos de sintaxe da consulta com base em método: Divisão (LINQ
Os exemplos neste tópico demonstram como usar Skip, SkipWhile, Take, e métodos de TakeWhile para ver DataSet usando a sintaxe da expressão de consulta.
O método FillDataSet usado nesses exemplos é especificado em Carregar dados em um DataSet.
Os exemplos neste tópico usam as tabelas Contact, Address, Product, SalesOrderHeader e SalesOrderDetail no banco de dados de exemplo AdventureWorks.
Os exemplos deste tópico usam as seguintes instruções using/Imports:
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
Para obter mais informações, consulte Como criar um projeto do LINQ to DataSet no Visual Studio.
Ignorar
Exemplo
Este exemplo usa o método de Skip para obter mas todos os cinco primeiros contatos da tabela de Contact .
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable contacts = ds.Tables["Contact"];
IEnumerable<DataRow> allButFirst5Contacts = contacts.AsEnumerable().Skip(5);
Console.WriteLine("All but first 5 contacts:");
foreach (DataRow contact in allButFirst5Contacts)
{
Console.WriteLine("FirstName = {0} \tLastname = {1}",
contact.Field<string>("FirstName"),
contact.Field<string>("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 contacts As DataTable = ds.Tables("Contact")
Dim allButFirst5Contacts = contacts.AsEnumerable().Skip(5)
Console.WriteLine("All but first 5 contacts:")
For Each contact In allButFirst5Contacts
Console.Write("FirstName = {0} ", contact.Field(Of String)("FirstName"))
Console.WriteLine(vbTab & " LastName = " & contact.Field(Of String)("LastName"))
Next
Exemplo
Este exemplo usa o método de Skip para obter todos mas os dois primeiros endereços em Seattle.
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable addresses = ds.Tables["Address"];
DataTable orders = ds.Tables["SalesOrderHeader"];
var query = (
from address in addresses.AsEnumerable()
from order in orders.AsEnumerable()
where address.Field<int>("AddressID") == order.Field<int>("BillToAddressID")
&& address.Field<string>("City") == "Seattle"
select new
{
City = address.Field<string>("City"),
OrderID = order.Field<int>("SalesOrderID"),
OrderDate = order.Field<DateTime>("OrderDate")
}).Skip(2);
Console.WriteLine("All but first 2 orders in Seattle:");
foreach (var order in query)
{
Console.WriteLine("City: {0} Order ID: {1} Total Due: {2:d}",
order.City, order.OrderID, order.OrderDate);
}
' 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 addresses As DataTable = ds.Tables("Address")
Dim orders As DataTable = ds.Tables("SalesOrderHeader")
Dim query = ( _
From address In addresses.AsEnumerable() _
From order In orders.AsEnumerable() _
Where (address.Field(Of Integer)("AddressID") = _
order.Field(Of Integer)("BillToAddressID")) _
And address.Field(Of String)("City") = "Seattle" _
Select New With _
{ _
.City = address.Field(Of String)("City"), _
.OrderID = order.Field(Of Integer)("SalesOrderID"), _
.OrderDate = order.Field(Of DateTime)("OrderDate") _
}).Skip(2)
Console.WriteLine("All but first 2 orders in Seattle:")
For Each addOrder In query
Console.Write("City: " & addOrder.City)
Console.Write(" Order ID: " & addOrder.OrderID)
Console.WriteLine(" Order date: " & addOrder.OrderDate)
Next
SkipWhile
Exemplo
Este exemplo usa OrderBy e métodos de SkipWhile para retornar produtos da tabela de Product com um custo de tabela maior que 300,00.
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable products = ds.Tables["Product"];
IEnumerable<DataRow> skipWhilePriceLessThan300 =
products.AsEnumerable()
.OrderBy(listprice => listprice.Field<decimal>("ListPrice"))
.SkipWhile(product => product.Field<decimal>("ListPrice") < 300.00M);
Console.WriteLine("Skip while ListPrice is less than 300.00:");
foreach (DataRow product in skipWhilePriceLessThan300)
{
Console.WriteLine(product.Field<decimal>("ListPrice"));
}
' 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 skipWhilePriceLessThan300 As IEnumerable(Of DataRow) = _
products.AsEnumerable() _
.OrderBy(Function(listprice) listprice.Field(Of Decimal)("ListPrice")) _
.SkipWhile(Function(product) product.Field(Of Decimal)("ListPrice") < 300D)
Console.WriteLine("First ListPrice less than 300.00:")
For Each product As DataRow In skipWhilePriceLessThan300
Console.WriteLine(product.Field(Of Decimal)("ListPrice"))
Next
Take
Exemplo
Este exemplo usa o método de Take para obter apenas os cinco primeiros contatos da tabela de Contact .
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable contacts = ds.Tables["Contact"];
IEnumerable<DataRow> first5Contacts = contacts.AsEnumerable().Take(5);
Console.WriteLine("First 5 contacts:");
foreach (DataRow contact in first5Contacts)
{
Console.WriteLine("Title = {0} \t FirstName = {1} \t Lastname = {2}",
contact.Field<string>("Title"),
contact.Field<string>("FirstName"),
contact.Field<string>("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 contacts As DataTable = ds.Tables("Contact")
Dim first5Contacts = contacts.AsEnumerable().Take(5)
Console.WriteLine("First 5 contacts:")
For Each contact In first5Contacts
Console.Write("Title = " & contact.Field(Of String)("Title"))
Console.Write(vbTab & "FirstName = " & contact.Field(Of String)("FirstName"))
Console.WriteLine(vbTab & "LastName = " & contact.Field(Of String)("LastName"))
Next
Exemplo
Este exemplo usa o método de Take para obter os três primeiros endereços em Seattle.
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable addresses = ds.Tables["Address"];
DataTable orders = ds.Tables["SalesOrderHeader"];
var query = (
from address in addresses.AsEnumerable()
from order in orders.AsEnumerable()
where address.Field<int>("AddressID") == order.Field<int>("BillToAddressID")
&& address.Field<string>("City") == "Seattle"
select new
{
City = address.Field<string>("City"),
OrderID = order.Field<int>("SalesOrderID"),
OrderDate = order.Field<DateTime>("OrderDate")
}).Take(3);
Console.WriteLine("First 3 orders in Seattle:");
foreach (var order in query)
{
Console.WriteLine("City: {0} Order ID: {1} Total Due: {2:d}",
order.City, order.OrderID, order.OrderDate);
}
' 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 addresses As DataTable = ds.Tables("Address")
Dim orders As DataTable = ds.Tables("SalesOrderHeader")
Dim query = ( _
From address In addresses.AsEnumerable() _
From order In orders.AsEnumerable() _
Where (address.Field(Of Integer)("AddressID") = _
order.Field(Of Integer)("BillToAddressID")) _
And address.Field(Of String)("City") = "Seattle" _
Select New With _
{ _
.City = address.Field(Of String)("City"), _
.OrderID = order.Field(Of Integer)("SalesOrderID"), _
.OrderDate = order.Field(Of DateTime)("OrderDate") _
}).Take(3)
Console.WriteLine("First 3 orders in Seattle:")
For Each order In query
Console.Write("City: " & order.City)
Console.Write(" Order ID: " & order.OrderID)
Console.WriteLine(" Order date: " & order.OrderDate)
Next
TakeWhile
Exemplo
Este exemplo usa OrderBy e TakeWhile para retornar produtos da tabela de Product com um custo de tabela menor que 300,00.
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable products = ds.Tables["Product"];
IEnumerable<DataRow> takeWhileListPriceLessThan300 =
products.AsEnumerable()
.OrderBy(listprice => listprice.Field<decimal>("ListPrice"))
.TakeWhile(product => product.Field<decimal>("ListPrice") < 300.00M);
Console.WriteLine("First ListPrice less than 300:");
foreach (DataRow product in takeWhileListPriceLessThan300)
{
Console.WriteLine(product.Field<decimal>("ListPrice"));
}
' 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 takeWhileListPriceLessThan300 As IEnumerable(Of DataRow) = _
products.AsEnumerable() _
.OrderBy(Function(listprice) listprice.Field(Of Decimal)("ListPrice")) _
.TakeWhile(Function(product) product.Field(Of Decimal)("ListPrice") < 300D)
Console.WriteLine("First ListPrice less than 300.00:")
For Each product As DataRow In takeWhileListPriceLessThan300
Console.WriteLine(product.Field(Of Decimal)("ListPrice"))
Next