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Ejemplos de sintaxis de expresiones de consulta: restricción (LINQ to DataSet)

Los ejemplos de este tema demuestran cómo usar el método Where para consultar un DataSet utilizando la sintaxis de la expresión de consulta.

El FillDataSet método usado en estos ejemplos se especifica en Carga de Datos en un DataSet.

Los ejemplos de este tema usan las tablas Contact, Address, Product, SalesOrderHeader y SalesOrderDetail de la base de datos de ejemplo AdventureWorks.

Los ejemplos de este tema utilizan las siguientes instrucciones 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;

Para obtener más información, vea How to: Create a LINQ to DataSet Project In Visual Studio.

Dónde

Ejemplo

En este ejemplo se devuelven todos los pedidos en línea.

// 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()
    where order.Field<bool>("OnlineOrderFlag") == true
    select new
    {
        SalesOrderID = order.Field<int>("SalesOrderID"),
        OrderDate = order.Field<DateTime>("OrderDate"),
        SalesOrderNumber = order.Field<string>("SalesOrderNumber")
    };

foreach (var onlineOrder in query)
{
    Console.WriteLine($"Order ID: {onlineOrder.SalesOrderID} Order date: {onlineOrder.OrderDate:d} Order number: {onlineOrder.SalesOrderNumber}");
}

' 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() _
    Where order.Field(Of Boolean)("OnlineOrderFlag") = True _
    Select New With { _
        .SalesOrderID = order.Field(Of Integer)("SalesOrderID"), _
        .OrderDate = order.Field(Of DateTime)("OrderDate"), _
        .SalesOrderNumber = order.Field(Of String)("SalesOrderNumber") _
     }

For Each onlineOrder In query
    Console.Write("Order ID: " & onlineOrder.SalesOrderID)
    Console.Write(" Order date: " & onlineOrder.OrderDate)
    Console.WriteLine(" Order number: " & onlineOrder.SalesOrderNumber)
Next

Ejemplo

En este ejemplo se devuelven los pedidos en los que la cantidad de pedidos es mayor que 2 y menor que 6.

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

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

var query =
    from order in orders.AsEnumerable()
    where order.Field<Int16>("OrderQty") > 2 &&
        order.Field<Int16>("OrderQty") < 6
    select new
    {
        SalesOrderID = (int)order.Field<int>("SalesOrderID"),
        OrderQty = order.Field<Int16>("OrderQty")
    };

foreach (var order in query)
{
    Console.WriteLine($"Order ID: {order.SalesOrderID} Order quantity: {order.OrderQty}");
}

' 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("SalesOrderDetail")

Dim query = _
    From order In orders.AsEnumerable() _
    Where order.Field(Of Short)("OrderQty") > 2 And _
            order.Field(Of Short)("OrderQty") < 6 _
    Select New With _
    { _
        .SalesOrderID = order.Field(Of Integer)("SalesOrderID"), _
        .OrderQty = order.Field(Of Short)("OrderQty") _
    }

For Each order In query
    Console.Write("Order ID: " & order.SalesOrderID)
    Console.WriteLine(" Order quantity: " & order.OrderQty)
Next

Ejemplo

En este ejemplo se devuelven todos los productos de color rojo.

// 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()
    where product.Field<string>("Color") == "Red"
    select new
    {
        Name = product.Field<string>("Name"),
        ProductNumber = product.Field<string>("ProductNumber"),
        ListPrice = product.Field<Decimal>("ListPrice")
    };

foreach (var product in query)
{
    Console.WriteLine($"Name: {product.Name}");
    Console.WriteLine($"Product number: {product.ProductNumber}");
    Console.WriteLine($"List price: ${product.ListPrice}");
    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 products As DataTable = ds.Tables("Product")

Dim query = _
    From product In products.AsEnumerable() _
    Where product.Field(Of String)("Color") = "Red" _
    Select New With _
       { _
           .Name = product.Field(Of String)("Name"), _
           .ProductNumber = product.Field(Of String)("ProductNumber"), _
           .ListPrice = product.Field(Of Decimal)("ListPrice") _
       }

For Each product In query
    Console.WriteLine("Name: " & product.Name)
    Console.WriteLine("Product number: " & product.ProductNumber)
    Console.WriteLine("List price: $ " & product.ListPrice & vbNewLine)
Next

Ejemplo

En este ejemplo se usa el Where método para buscar pedidos realizados después del 1 de diciembre de 2002 y, a continuación, se usa el GetChildRows método para obtener los detalles de cada pedido.

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

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

IEnumerable<DataRow> query =
    from order in orders.AsEnumerable()
    where order.Field<DateTime>("OrderDate") >= new DateTime(2002, 12, 1)
    select order;

Console.WriteLine("Orders that were made after 12/1/2002:");
foreach (DataRow order in query)
{
    Console.WriteLine($"OrderID {order.Field<int>("SalesOrderID")} Order date: {order.Field<DateTime>("OrderDate"):d} ");
    foreach (DataRow orderDetail in order.GetChildRows("SalesOrderHeaderDetail"))
    {
        Console.WriteLine($"  Product ID: {orderDetail["ProductID"]} Unit Price {orderDetail["UnitPrice"]}");
    }
}

' 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 As IEnumerable(Of DataRow) = _
    From order In orders.AsEnumerable() _
    Where order.Field(Of DateTime)("OrderDate") >= New DateTime(2002, 12, 1) _
    Select order

Console.WriteLine("Orders that were made after 12/1/2002:")
For Each order As DataRow In query
    Console.WriteLine("OrderID {0} Order date: {1:d} ", _
        order.Field(Of Integer)("SalesOrderID"), order.Field(Of DateTime)("OrderDate"))
    For Each orderDetail As DataRow In order.GetChildRows("SalesOrderHeaderDetail")
        Console.WriteLine("  Product ID: {0} Unit Price {1}", _
            orderDetail("ProductID"), orderDetail("UnitPrice"))
    Next
Next

Consulte también