本主题提供有关如何提供现有 EntityConnection 以供对象上下文使用的示例。 有关更多信息，请参见连接字符串（实体框架）。
本主题中的示例基于 AdventureWorks 销售模型。 若要运行本示例中的代码，必须已将 AdventureWorks 销售模型添加到您的项目中，并将项目配置为使用实体框架。 为此，请完成如何：使用实体数据模型向导（实体框架） 中的过程。
示例
本示例创建一个 EntityConnection，它将被传递到长时间运行的 ObjectContext 的构造函数中。 此连接以手动方式建立。 EntityConnection 和 ObjectContext 均以手动方式释放。
' Define the order ID for the order we want.
Dim orderId As Integer = 43680
' Create an EntityConnection.
Dim conn As New EntityConnection("name=AdventureWorksEntities")
' Create a long-running context with the connection.
Dim context As New AdventureWorksEntities(conn)
Try
' Explicitly open the connection.
If conn.State <> ConnectionState.Open Then
conn.Open()
End If
' Execute a query to return an order.
Dim order As SalesOrderHeader = context.SalesOrderHeaders.Where("it.SalesOrderID = @orderId", _
New ObjectParameter("orderId", orderId)).Execute(MergeOption.AppendOnly).First()
' Change the status of the order.
order.Status = 1
' You do not have to call the Load method to load the details for the order,
' because lazy loading is set to true
' by the constructor of the AdventureWorksEntities object.
' With lazy loading set to true the related objects are loaded when
' you access the navigation property. In this case SalesOrderDetails.
' Delete the first item in the order.
context.DeleteObject(order.SalesOrderDetails.First())
' Save changes.
If 0 < context.SaveChanges() Then
Console.WriteLine("Changes saved.")
End If
' Create a new SalesOrderDetail object.
' You can use the static CreateObjectName method (the Entity Framework
' adds this method to the generated entity types) instead of the new operator:
' SalesOrderDetail.CreateSalesOrderDetail(1, 0, 2, 750, 1, (decimal)2171.2942, 0, 0,
' Guid.NewGuid(), DateTime.Today));
Dim detail = New SalesOrderDetail With
{
.SalesOrderID = 0,
.SalesOrderDetailID = 0,
.OrderQty = 2,
.ProductID = 750,
.SpecialOfferID = 1,
.UnitPrice = CDec(2171.2942),
.UnitPriceDiscount = 0,
.LineTotal = 0,
.rowguid = Guid.NewGuid(),
.ModifiedDate = DateTime.Now
}
order.SalesOrderDetails.Add(detail)
' Save changes again.
If 0 < context.SaveChanges() Then
Console.WriteLine("Changes saved.")
End If
Catch ex As InvalidOperationException
Console.WriteLine(ex.ToString())
Finally
' Explicitly dispose of the context and the connection.
context.Dispose()
conn.Dispose()
// Define the order ID for the order we want.
int orderId = 43680;
// Create an EntityConnection.
EntityConnection conn =
new EntityConnection("name=AdventureWorksEntities");
// Create a long-running context with the connection.
AdventureWorksEntities context =
new AdventureWorksEntities(conn);
try
{
// Explicitly open the connection.
if (conn.State != ConnectionState.Open)
{
conn.Open();
}
// Execute a query to return an order.
SalesOrderHeader order =
context.SalesOrderHeaders.Where(
"it.SalesOrderID = @orderId", new ObjectParameter("orderId", orderId))
.Execute(MergeOption.AppendOnly).First();
// Change the status of the order.
order.Status = 1;
// You do not have to call the Load method to load the details for the order,
// because lazy loading is set to true
// by the constructor of the AdventureWorksEntities object.
// With lazy loading set to true the related objects are loaded when
// you access the navigation property. In this case SalesOrderDetails.
// Delete the first item in the order.
context.DeleteObject(order.SalesOrderDetails.First());
// Save changes.
if (0 < context.SaveChanges())
{
Console.WriteLine("Changes saved.");
}
// Create a new SalesOrderDetail object.
// You can use the static CreateObjectName method (the Entity Framework
// adds this method to the generated entity types) instead of the new operator:
// SalesOrderDetail.CreateSalesOrderDetail(1, 0, 2, 750, 1, (decimal)2171.2942, 0, 0,
// Guid.NewGuid(), DateTime.Today));
SalesOrderDetail detail = new SalesOrderDetail
{
SalesOrderID = 1,
SalesOrderDetailID = 0,
OrderQty = 2,
ProductID = 750,
SpecialOfferID = 1,
UnitPrice = (decimal)2171.2942,
UnitPriceDiscount = 0,
LineTotal = 0,
rowguid = Guid.NewGuid(),
ModifiedDate = DateTime.Now
};
order.SalesOrderDetails.Add(detail);
// Save changes again.
if (0 < context.SaveChanges())
{
Console.WriteLine("Changes saved.");
}
}
catch (InvalidOperationException ex)
{
Console.WriteLine(ex.ToString());
}
finally
{
// Explicitly dispose of the context and the connection.
context.Dispose();
conn.Dispose();
}