ObjectDataSource.Deleting 事件
定义
重要
一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。 对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。
在 Delete() 操作前发生。
public:
event System::Web::UI::WebControls::ObjectDataSourceMethodEventHandler ^ Deleting;public event System.Web.UI.WebControls.ObjectDataSourceMethodEventHandler Deleting;member this.Deleting : System.Web.UI.WebControls.ObjectDataSourceMethodEventHandler Public Custom Event Deleting As ObjectDataSourceMethodEventHandler 事件类型
示例
本部分包含两个代码示例。 第一个 ObjectDataSource 代码示例演示如何将 对象与业务对象和控件一 GridView 起使用来删除数据。 第二个代码示例演示在第 EmployeeLogic 一个代码示例中使用的类。
下面的代码示例演示如何将 ObjectDataSource 控件与业务对象和控件一 GridView 起使用来删除数据。 最初， GridView 控件显示一组所有员工，使用 属性 SelectMethod 指定的 方法从 EmployeeLogic 对象检索数据。 由于 属性 AutoGenerateDeleteButton 设置为 true，因此控件 GridView 会自动显示 “删除” 按钮。
如果单击“ 删除” 按钮，将使用 属性指定的 DeleteMethod 方法和集合中指定的 DeleteParameters 任何参数执行删除操作。 在此代码示例中，还执行了一些预处理和后处理步骤。 调用 NorthwindEmployeeDeleting 委托以在执行操作之前处理 Deleting 事件，调用 NorthwindEmployeeDeleted 委托以在操作完成后处理 Deleted 事件以执行异常处理。 在此代码示例中，如果 NorthwindDataException 引发 ，则由 NorthwindEmployeeDeleted 方法处理。
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.CS" Assembly="Samples.AspNet.CS" %>
<%@ Import namespace="Samples.AspNet.CS" %>
<%@ Page language="c#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
private void NorthwindEmployeeDeleting(object source, ObjectDataSourceMethodEventArgs e)
{
// The GridView passes the ID of the employee
// to be deleted. However, the buisiness object, EmployeeLogic,
// requires a NorthwindEmployee parameter, named "ne". Create
// it now and add it to the parameters collection.
IDictionary paramsFromPage = e.InputParameters;
if (paramsFromPage["EmpID"] != null) {
NorthwindEmployee ne
= new NorthwindEmployee( Int32.Parse(paramsFromPage["EmpID"].ToString()));
// Remove the old EmpID parameter.
paramsFromPage.Clear();
paramsFromPage.Add("ne", ne);
}
}
private void NorthwindEmployeeDeleted(object source, ObjectDataSourceStatusEventArgs e)
{
// Handle the Exception if it is a NorthwindDataException
if (e.Exception != null)
{
// Handle the specific exception type. The ObjectDataSource wraps
// any Exceptions in a TargetInvokationException wrapper, so
// check the InnerException property for expected Exception types.
if (e.Exception.InnerException is NorthwindDataException)
{
Label1.Text = e.Exception.InnerException.Message;
// Because the exception is handled, there is
// no reason to throw it.
e.ExceptionHandled = true;
}
}
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title>ObjectDataSource - C# Example</title>
</head>
<body>
<form id="Form1" method="post" runat="server">
<asp:gridview
id="GridView1"
runat="server"
datasourceid="ObjectDataSource1"
autogeneratedeletebutton="true"
autogeneratecolumns="false"
datakeynames="EmpID">
<columns>
<asp:boundfield headertext="EmpID" datafield="EmpID" />
<asp:boundfield headertext="First Name" datafield="FirstName" />
<asp:boundfield headertext="Last Name" datafield="LastName" />
</columns>
</asp:gridview>
<asp:objectdatasource
id="ObjectDataSource1"
runat="server"
selectmethod="GetAllEmployees"
deletemethod="DeleteEmployee"
ondeleting="NorthwindEmployeeDeleting"
ondeleted="NorthwindEmployeeDeleted"
typename="Samples.AspNet.CS.EmployeeLogic">
<deleteparameters>
<asp:parameter name="EmpID" type="Int32" />
</deleteparameters>
</asp:objectdatasource>
<asp:label id="Label1" runat="server" />
</form>
</body>
</html>
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.VB" Assembly="Samples.AspNet.VB" %>
<%@ Import namespace="Samples.AspNet.VB" %>
<%@ Page language="vb" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
' Called before a Delete operation.
Private Sub NorthwindEmployeeDeleting(ByVal source As Object, ByVal e As ObjectDataSourceMethodEventArgs)
' The GridView passes the ID of the employee
' to be deleted. However, the business object, EmployeeLogic,
' requires a NorthwindEmployee parameter, named "ne". Create
' it now and add it to the parameters collection.
Dim paramsFromPage As IDictionary = e.InputParameters
If Not paramsFromPage("EmpID") Is Nothing Then
Dim ne As New NorthwindEmployee(paramsFromPage("EmpID").ToString())
' Remove the old EmpID parameter.
paramsFromPage.Clear()
paramsFromPage.Add("ne", ne)
End If
End Sub ' NorthwindEmployeeDeleting
' Called after a Delete operation.
Private Sub NorthwindEmployeeDeleted(ByVal source As Object, ByVal e As ObjectDataSourceStatusEventArgs)
' Handle the Exception if it is a NorthwindDataException.
If Not e.Exception Is Nothing Then
' Handle the specific exception type. The ObjectDataSource wraps
' any Exceptions in a TargetInvokationException wrapper, so
' check the InnerException property for the expected Exception types.
If e.Exception.InnerException.GetType().Equals(GetType(NorthwindDataException)) Then
Label1.Text = e.Exception.InnerException.Message
' Because the exception is handled, there is
' no reason to throw it.
e.ExceptionHandled = True
End If
End If
End Sub ' NorthwindEmployeeDeleted
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title>ObjectDataSource - VB Example</title>
</head>
<body>
<form id="Form1" method="post" runat="server">
<asp:gridview
id="GridView1"
runat="server"
datasourceid="ObjectDataSource1"
autogeneratedeletebutton="true"
autogeneratecolumns="false"
datakeynames="EmpID">
<columns>
<asp:boundfield headertext="EmpID" datafield="EmpID" />
<asp:boundfield headertext="First Name" datafield="FirstName" />
<asp:boundfield headertext="Last Name" datafield="LastName" />
</columns>
</asp:gridview>
<asp:objectdatasource
id="ObjectDataSource1"
runat="server"
selectmethod="GetAllEmployees"
deletemethod="DeleteEmployee"
ondeleting="NorthwindEmployeeDeleting"
ondeleted="NorthwindEmployeeDeleted"
typename="Samples.AspNet.VB.EmployeeLogic">
<deleteparameters>
<asp:parameter name="EmpID" type="Int32" />
</deleteparameters>
</asp:objectdatasource>
<asp:label id="Label1" runat="server" />
</form>
</body>
</html>
下面的代码示例演示在 EmployeeLogic 前面的代码示例中使用的 类。
namespace Samples.AspNet.CS {
using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Web.UI;
using System.Web.UI.WebControls;
//
// EmployeeLogic is a stateless business object that encapsulates
// the operations you can perform on a NorthwindEmployee object.
//
public class EmployeeLogic {
// Returns a collection of NorthwindEmployee objects.
public static ICollection GetAllEmployees () {
ArrayList al = new ArrayList();
// Use the SqlDataSource class to wrap the
// ADO.NET code required to query the database.
ConnectionStringSettings cts = ConfigurationManager.ConnectionStrings["NorthwindConnection"];
SqlDataSource sds
= new SqlDataSource(cts.ConnectionString,
"SELECT EmployeeID FROM Employees");
try {
IEnumerable IDs = sds.Select(DataSourceSelectArguments.Empty);
// Iterate through the Enumeration and create a
// NorthwindEmployee object for each ID.
IEnumerator enumerator = IDs.GetEnumerator();
while (enumerator.MoveNext()) {
// The IEnumerable contains DataRowView objects.
DataRowView row = enumerator.Current as DataRowView;
string id = row["EmployeeID"].ToString();
NorthwindEmployee nwe = new NorthwindEmployee(id);
// Add the NorthwindEmployee object to the collection.
al.Add(nwe);
}
}
finally {
// If anything strange happens, clean up.
sds.Dispose();
}
return al;
}
public static NorthwindEmployee GetEmployee(object anID) {
return new NorthwindEmployee(anID);
}
public static void DeleteEmployee(NorthwindEmployee ne) {
bool retval = ne.Delete();
if (! retval) { throw new NorthwindDataException("Employee delete failed."); }
// Delete the object in memory.
ne = null;
}
public static void DeleteEmployeeByID(int anID) {
NorthwindEmployee tempEmp = new NorthwindEmployee(anID);
DeleteEmployee(tempEmp);
}
}
public class NorthwindEmployee {
public NorthwindEmployee () {
ID = DBNull.Value;
lastName = "";
firstName = "";
}
public NorthwindEmployee (object anID) {
this.ID = anID;
ConnectionStringSettings cts = ConfigurationManager.ConnectionStrings["NorthwindConnection"];
SqlConnection conn = new SqlConnection (cts.ConnectionString);
SqlCommand sc =
new SqlCommand(" SELECT FirstName,LastName " +
" FROM Employees " +
" WHERE EmployeeID = @empId",
conn);
// Add the employee ID parameter and set its value.
sc.Parameters.Add(new SqlParameter("@empId",SqlDbType.Int)).Value = Int32.Parse(anID.ToString());
SqlDataReader sdr = null;
try {
conn.Open();
sdr = sc.ExecuteReader();
// This is not a while loop. It only loops once.
if (sdr != null && sdr.Read()) {
// The IEnumerable contains DataRowView objects.
this.firstName = sdr["FirstName"].ToString();
this.lastName = sdr["LastName"].ToString();
}
else {
throw new NorthwindDataException("Data not loaded for employee id.");
}
}
finally {
try {
if (sdr != null) sdr.Close();
conn.Close();
}
catch (SqlException) {
// Log an event in the Application Event Log.
throw;
}
}
}
private object ID;
public object EmpID {
get { return ID; }
}
private string lastName;
public string LastName {
get { return lastName; }
set { lastName = value; }
}
private string firstName;
public string FirstName {
get { return firstName; }
set { firstName = value; }
}
public bool Delete () {
if (ID.Equals(DBNull.Value)) {
// The Employee object is not persisted.
return true;
}
else {
// The Employee object is persisted.
// Use the SqlDataSource control as a convenient wrapper for
// the ADO.NET code needed to delete a record from the database.
ConnectionStringSettings cts = ConfigurationManager.ConnectionStrings["NorthwindConnection"];
SqlDataSource sds = new SqlDataSource();
try {
sds.ConnectionString = cts.ConnectionString;
sds.DeleteParameters.Add(new Parameter("empID", TypeCode.Int32, this.ID.ToString()));
sds.DeleteCommand = "DELETE FROM [Order Details] " +
"WHERE OrderID IN (SELECT OrderID FROM Orders WHERE EmployeeID=@empID)";
sds.Delete();
sds.DeleteCommand = "DELETE FROM Orders WHERE EmployeeID=@empID";
sds.Delete();
sds.DeleteCommand = "DELETE FROM EmployeeTerritories WHERE EmployeeID=@empID";
sds.Delete();
sds.DeleteCommand = "DELETE FROM Employees WHERE EmployeeID=@empID";
sds.Delete();
return true;
}
finally {
// Clean up resources.
sds.Dispose();
}
}
}
}
public class NorthwindDataException: Exception {
public NorthwindDataException(string msg) : base (msg) { }
}
}
Imports System.Collections
Imports System.Configuration
Imports System.Data
Imports System.Data.SqlClient
Imports System.Web.UI
Imports System.Web.UI.WebControls
Namespace Samples.AspNet.VB
'
' EmployeeLogic is a stateless business object that encapsulates
' the operations you can perform on a NorthwindEmployee object.
Public Class EmployeeLogic
' Return a collection of NorthwindEmployee objects.
Public Shared Function GetAllEmployees() As ICollection
Dim al As New ArrayList()
' Use the SqlDataSource class to wrap the
' ADO.NET code required to query the database.
Dim cts As ConnectionStringSettings = ConfigurationManager.ConnectionStrings("NorthwindConnection")
Dim sds As New SqlDataSource(cts.ConnectionString, _
"SELECT EmployeeID FROM Employees")
Try
Dim IDs As IEnumerable = sds.Select(DataSourceSelectArguments.Empty)
' Iterate through the Enumeration and create a
' NorthwindEmployee object for each ID.
Dim enumerator As IEnumerator = IDs.GetEnumerator()
While enumerator.MoveNext()
' The IEnumerable contains DataRowView objects.
Dim row As DataRowView = CType(enumerator.Current,DataRowView)
Dim id As String = row("EmployeeID").ToString()
Dim nwe As New NorthwindEmployee(id)
' Add the NorthwindEmployee object to the collection.
al.Add(nwe)
End While
Finally
' If anything strange happens, clean up.
sds.Dispose()
End Try
Return al
End Function 'GetAllEmployees
Public Shared Function GetEmployee(anID As Object) As NorthwindEmployee
Return New NorthwindEmployee(anID)
End Function 'GetEmployee
Public Shared Sub DeleteEmployee(ne As NorthwindEmployee)
Dim retval As Boolean = ne.Delete()
If Not retval Then
Throw New NorthwindDataException("Employee delete failed.")
End If ' Delete the object in memory.
ne = Nothing
End Sub
Public Shared Sub DeleteEmployeeByID(anID As Integer)
Dim tempEmp As New NorthwindEmployee(anID)
DeleteEmployee(tempEmp)
End Sub
End Class
Public Class NorthwindEmployee
Public Sub New()
ID = DBNull.Value
aLastName = ""
aFirstName = ""
End Sub
Public Sub New(anID As Object)
Me.ID = anID
Dim cts As ConnectionStringSettings = ConfigurationManager.ConnectionStrings("NorthwindConnection")
Dim conn As New SqlConnection(cts.ConnectionString)
Dim sc As New SqlCommand(" SELECT FirstName,LastName " & _
" FROM Employees " & _
" WHERE EmployeeID = @empId", conn)
' Add the employee ID parameter and set its value.
sc.Parameters.Add(New SqlParameter("@empId", SqlDbType.Int)).Value = Int32.Parse(anID.ToString())
Dim sdr As SqlDataReader = Nothing
Try
conn.Open()
sdr = sc.ExecuteReader()
' This is not a while loop. It only loops once.
If Not (sdr Is Nothing) AndAlso sdr.Read() Then
' The IEnumerable contains DataRowView objects.
Me.aFirstName = sdr("FirstName").ToString()
Me.aLastName = sdr("LastName").ToString()
Else
Throw New NorthwindDataException("Data not loaded for employee id.")
End If
Finally
Try
If Not (sdr Is Nothing) Then
sdr.Close()
End If
conn.Close()
Catch se As SqlException
' Log an event in the Application Event Log.
Throw
End Try
End Try
End Sub
Private ID As Object
Public ReadOnly Property EmpID() As Object
Get
Return ID
End Get
End Property
Private aLastName As String
Public Property LastName() As String
Get
Return aLastName
End Get
Set
aLastName = value
End Set
End Property
Private aFirstName As String
Public Property FirstName() As String
Get
Return aFirstName
End Get
Set
aFirstName = value
End Set
End Property
Public Function Delete() As Boolean
If ID.Equals(DBNull.Value) Then
' The Employee object is not persisted.
Return True
Else
' The Employee object is persisted.
' Use the SqlDataSource control as a convenient wrapper for
' the ADO.NET code needed to delete a record from the database.
Dim cts As ConnectionStringSettings = ConfigurationManager.ConnectionStrings("NorthwindConnection")
Dim sds As New SqlDataSource()
Try
sds.ConnectionString = cts.ConnectionString
sds.DeleteParameters.Add(New Parameter("empID", TypeCode.Int32, Me.ID.ToString()))
sds.DeleteCommand = "DELETE FROM [Order Details] " & _
"WHERE OrderID IN (SELECT OrderID FROM Orders WHERE EmployeeID=@empID)"
sds.Delete()
sds.DeleteCommand = "DELETE FROM Orders WHERE EmployeeID=@empID"
sds.Delete()
sds.DeleteCommand = "DELETE FROM EmployeeTerritories WHERE EmployeeID=@empID"
sds.Delete()
sds.DeleteCommand = "DELETE FROM Employees WHERE EmployeeID=@empID"
sds.Delete()
Return True
Finally
' Clean up resources.
sds.Dispose()
End Try
End If
End Function 'Delete
End Class
Public Class NorthwindDataException
Inherits Exception
Public Sub New(msg As String)
MyBase.New(msg)
End Sub
End Class
End Namespace
注解
Deleting处理 事件以执行特定于应用程序的其他初始化、验证参数的值或在控件执行删除操作之前ObjectDataSource更改参数值。 参数可用作 IDictionary 由 属性访问 InputParameters 的集合，该属性由 ObjectDataSourceMethodEventArgs 对象公开。
可以通过将 的 ObjectDataSourceMethodEventArgs 属性设置为 Cancel 来true取消删除操作。
有关如何处理事件的详细信息，请参阅 处理和引发事件。
