How to: Bind Objects to Windows Form Controls (Entity Framework)

Articolo
04/21/2009

Object Services enables you to bind Windows Form controls such as a ComboBox or DataGridView to an EntityCollection or to an ObjectQuery result. We recommend that you not bind controls directly to an ObjectQuery. Instead, bind controls to the result of the Execute method. For more information, see Binding Objects to Controls (Entity Framework).

The example in this topic is based on the Adventure Works Sales Model. To run the code in this example, you must have already added the AdventureWorks Sales Model to your project and configured your project to use the Entity Framework. To do this, complete the procedures in How to: Manually Configure an Entity Framework Project and How to: Manually Define an Entity Data Model (Entity Framework).

Example

The following example is from a Windows Form. When the form is loaded, an ObjectResult of SalesOrderHeader objects is returned by calling the Execute method of the ObjectQuery. This result is bound to a combo box. When an order is selected, the related EntityCollection of SalesOrderDetail objects is bound to a DataGridView control.

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

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")

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

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

        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;

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");

                // Display the PO number in the combo box.
                this.ordersListBox.DisplayMember = "PurchaseOrderNumber";

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

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How to: Bind Objects to Windows Form Controls (Entity Framework)

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