Cómo enlazar objetos a controles de Windows Forms (Entity Framework)

Servicios de objeto permite enlazar controles de formularios Windows Forms como ComboBox o DataGridView a EntityCollection o al resultado de ObjectQuery. We recommend that you not bind controls directly to an ObjectQuery. En su lugar, enlace controles al resultado del método Execute. Para obtener más información, vea Enlazar objetos a controles (Entity Framework).

El ejemplo de este tema se basa en el modelo AdventureWorks Sales. Para ejecutar el código de este ejemplo, debe haber agregado ya el modelo AdventureWorks Sales al proyecto y haber configurado el proyecto para usar Entity Framework. Para ello, complete los procedimientos de Cómo configurar manualmente un proyecto de Entity Framework y Cómo definir manualmente un modelo Entity Data Model (Entity Framework).

Ejemplo

El ejemplo siguiente es de un formulario de Windows Forms. Cuando se carga el formulario, se devuelve un ObjectResult de objetos SalesOrderHeader llamando al método Execute de ObjectQuery. Este resultado se enlaza a un cuadro combinado. Cuando se selecciona un pedido, la EntityCollection relacionada de objetos SalesOrderDetail se enlaza a un control DataGridView.

Imports System
Imports System.Collections.Generic
Imports System.Collections
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Linq
Imports System.Text
Imports System.Windows.Forms
Imports System.Data.Objects
Imports System.Data.Objects.DataClasses
Imports AdventureWorksModel

Public Class Main
    Public Sub New()
        ' Initializes the designer-generated controls.
        InitializeComponent()
    End Sub
    Private context As AdventureWorksEntities
    Private customerId As Integer = 277
    Private Sub Main_Load(ByVal sender As System.Object, _
                           ByVal e As System.EventArgs) _
                           Handles MyBase.Load
        ' Initialize the object context.
        context = New AdventureWorksEntities()
        Try
            ' Create a query for orders that includes line items.
            Dim orderQuery As ObjectQuery(Of SalesOrderHeader) = _
            context.SalesOrderHeader _
                    .Where("it.CustomerID = @customerId", _
                    New ObjectParameter("customerId", customerId)) _
            .Include("SalesOrderDetail")

            ' Bind the combo box to the ObjectResult of SalesOrderHeader 
            ' that is returned when the query is executed.
            Me.ordersListBox.DataSource = orderQuery.Execute(MergeOption.AppendOnly)

            ' Display the PO number in the combo box.
            Me.ordersListBox.DisplayMember = "PurchaseOrderNumber"

        Catch ex As EntitySqlException
            MessageBox.Show(ex.Message)
        End Try
    End Sub
    Private Sub ordersListBox_SelectedIndexChanged(ByVal sender As System.Object, _
                                                    ByVal e As System.EventArgs) _
                                                    Handles ordersListBox.SelectedIndexChanged
        ' Get the currently selected SalesOrderHeader object.
        Dim order As SalesOrderHeader = CType(Me.ordersListBox.SelectedItem,  _
        SalesOrderHeader)

        ' Bind the items for this order to the DataGridView.
        lineItemsDataGrid.DataSource = order.SalesOrderDetail
    End Sub

    Private Sub saveButton_Click(ByVal sender As System.Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles saveButton.Click
        ' Get the current order. 
        Dim order As SalesOrderHeader = CType(ordersListBox.SelectedItem,  _
            SalesOrderHeader)

        Try
            ' Save changes in the object context.
            context.SaveChanges(True)

        Catch ex As OptimisticConcurrencyException
            ' Resolve the concurrently conflict by refreshing the 
            ' object context before saving changes. 
            context.Refresh(RefreshMode.ClientWins, order.SalesOrderDetail)

            ' Resave changes in the object context.
            context.SaveChanges(True)
        Catch ex As Exception
            MessageBox.Show(ex.InnerException.Message, "An error has occured")
        Finally
            ' Refresh the latest data from the database.
            context.Refresh(RefreshMode.StoreWins, order)
            Me.Refresh()
        End Try
    End Sub
End Class

using System;
using System.Collections.Generic;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.Objects;
using System.Data.Objects.DataClasses;
using AdventureWorksModel;

namespace Microsoft.Samples.Edm
{
    public partial class Main : Form
    {
        private AdventureWorksEntities context;
        private int customerId = 277;

        public Main()
        {
            // Initializes the designer-generated controls.
            InitializeComponent();
        }
        
        private void Main_Load(object sender, EventArgs e)
        {
            // Initialize the object context.
            context = new AdventureWorksEntities();
            try
            {
                // Create a query for orders that includes line items.
                ObjectQuery<SalesOrderHeader> orderQuery = context.SalesOrderHeader
                    .Where("it.CustomerID = @customerId", 
                    new ObjectParameter("customerId", customerId))
                    .Include("SalesOrderDetail");

                // Bind the combo box to the ObjectResult of SalesOrderHeader 
                // that is returned when the query is executed.
                this.ordersListBox.DataSource = orderQuery.Execute(MergeOption.AppendOnly);

                // Display the PO number in the combo box.
                this.ordersListBox.DisplayMember = "PurchaseOrderNumber";
            }
            catch (EntitySqlException ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

        private void ordersListBox_SelectedIndexChanged(object sender, EventArgs e)
        {
            // Get the currently selected SalesOrderHeader object.
            SalesOrderHeader order = (SalesOrderHeader)this.ordersListBox.SelectedItem;

            // Bind the items for this order to the DataGridView.
            lineItemsDataGrid.DataSource = order.SalesOrderDetail;
        }

        private void saveButton_Click(object sender, EventArgs e)
        {
            // Get the current order.    
            SalesOrderHeader order = (SalesOrderHeader)ordersListBox.SelectedItem;

            try
            {
                // Save changes in the object context.
                context.SaveChanges(true);
            }
            catch (OptimisticConcurrencyException)
            {
                // Resolve the concurrently conflict by refreshing the 
                // object context before saving changes. 
                context.Refresh(RefreshMode.ClientWins, order.SalesOrderDetail);

                // Resave changes in the object context.
                context.SaveChanges(true);
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.InnerException.Message, "An error has occured");
            }
            finally
            {
                //  Refresh the latest data from the database.
                context.Refresh(RefreshMode.StoreWins, order);
                this.Refresh();
            }
        }
    }
}

Vea también

Tareas

Cómo enlazar objetos a controles de Windows Presentation Foundation (Entity Framework)
Cómo agregar un objeto como origen de datos del proyecto (Entity Framework)

Conceptos

Enlazar objetos a controles (Entity Framework)
Enlazar datos de entidad a controles (escenarios de aplicación)