Two-way data binding in ASP.NET
Trying to use data binding between a list of objects and a data list control. What I want to do are
- create the list of objects
- have them bound to the controls
- change data in the UI
- have the changes in the ui bound to the list of objects
- on post back - have the list of objects with the new values from the ui
<body>
<form id="form1" runat="server">
<div>
<asp:DataList ID="DataList1" runat="server" DataKeyField="ClassID" ViewStateMode="Enabled">
<ItemTemplate>
<asp:TextBox ID="txtValue1" runat="server" Text='<%# Bind("Value1") %>'开发者_如何学运维></asp:TextBox>
<asp:TextBox ID="txtValue2" runat="server" Text='<%# Bind("Value2") %>'></asp:TextBox>
<asp:TextBox ID="txtvalue3" runat="server" Text='<%# Bind("Value3") %>'></asp:TextBox>
</ItemTemplate>
</asp:DataList>
<asp:Button ID="btnDoPostBack" runat="server" Text="Do Post Back" />
</div>
</form>
</body>
Option Explicit On
Option Strict On
Imports System.Diagnostics
Partial Class _Default
Inherits System.Web.UI.Page
Dim Class1List As List(Of Class1)
Protected Sub Page_PreLoad(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreLoad
Dim txtValue1 As TextBox
Dim txtValue2 As TextBox
Dim txtValue3 As TextBox
Dim ItemIndex As Integer = 0
If Page.IsPostBack Then
Class1List = CType(Session("Class1List"), List(Of Global.Class1))
'Class1List = CType(DataList1.DataSource, List(Of Global.Class1))
For Each myDataListItem As DataListItem In DataList1.Items
txtValue1 = CType(myDataListItem.FindControl("txtValue1"), TextBox)
Long.TryParse(txtValue1.Text, Class1List(ItemIndex).Value1)
txtValue2 = CType(myDataListItem.FindControl("txtValue2"), TextBox)
Integer.TryParse(txtValue2.Text, Class1List(ItemIndex).Value2)
txtValue3 = CType(myDataListItem.FindControl("txtValue3"), TextBox)
Class1List(ItemIndex).Value3 = txtValue3.Text
ItemIndex += 1
Next
End If
End Sub
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim myClass1 As Class1
If Not Page.IsPostBack Then
Class1List = New List(Of Class1)
myClass1 = New Class1
Class1List.Add(myClass1)
BindData()
Else
'Class1List = CType(DataList1.DataSource, List(Of Global.Class1))
Debug.WriteLine("Page_Load, Value1 = " & Class1List(0).Value1.ToString())
Debug.WriteLine("Page_Load, Value2 = " & Class1List(0).Value2.ToString())
Debug.WriteLine("Page_Load, Value3 = " & Class1List(0).Value3)
End If
End Sub
Protected Sub Page_Unload(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Unload
Session("Class1List") = Class1List
End Sub
Sub BindData()
DataList1.DataSource = Class1List
DataList1.DataBind()
End Sub
Protected Sub DataList1_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.DataListItemEventArgs) Handles DataList1.ItemDataBound
Dim myClass1 As Class1
If e.Item.ItemType = ListItemType.Item OrElse e.Item.ItemType = ListItemType.AlternatingItem Then
myClass1 = CType(e.Item.DataItem, Class1)
Debug.WriteLine("DataList1_ItemDataBound, Value1 = " & myClass1.Value1.ToString())
Debug.WriteLine("DataList1_ItemDataBound, Value2 = " & myClass1.Value2.ToString())
Debug.WriteLine("DataList1_ItemDataBound, Value3 = " & myClass1.Value3)
End If
End Sub
Protected Sub btnDoPostBack_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnDoPostBack.Click
Dim myRandom As New Random
Class1List(0).Value1 = myRandom.Next(100)
Class1List(0).Value2 = myRandom.Next(100)
Class1List(0).Value3 = myRandom.Next(100).ToString()
Debug.WriteLine("btnDoPostBack_Click, Value1 = " & Class1List(0).Value1.ToString())
Debug.WriteLine("btnDoPostBack_Click, Value2 = " & Class1List(0).Value2.ToString())
Debug.WriteLine("btnDoPostBack_Click, Value3 = " & Class1List(0).Value3)
BindData()
End Sub
End Class
The Class Class1 is trivial:
Option Explicit On
Option Strict On
Imports Microsoft.VisualBasic
Public Class Class1
Private _ClassID As Long
Private _Value1 As Long
Private _Value2 As Integer
Private _value3 As String = String.Empty
Public Property ClassID As Long
Get
Return _ClassID
End Get
Set(ByVal value As Long)
_ClassID = value
End Set
End Property
Public Property Value1 As Long
Get
Return _Value1
End Get
Set(ByVal value As Long)
_Value1 = value
End Set
End Property
Public Property Value2 As Integer
Get
Return _Value2
End Get
Set(ByVal value As Integer)
_Value2 = value
End Set
End Property
Public Property Value3 As String
Get
Return _value3
End Get
Set(ByVal value As String)
_value3 = value
End Set
End Property
End Class
Update: I got the code behind above to do what I want it to do - I was thinking there was a better way?
You didn't show your databinding "Load" phase (the code which binds the data from the list to the controls)--so I assume the part you are unhappy with is the "Save" phase (the code in Page_PreLoad which binds the modified values from the controls back to the list), i.e. #4 in your list:
have the changes in the ui bound to the list of objects
It sounds like you want "two-way Data Binding": you want .NET to update your model as easily as it reads from your model. This is a common complaint. One solution is to subclass WebControl, but that's a mess.
You are already using the <%# Bind("...") %> syntax, so you have the right idea. That approach should work out-of-the-box with <asp:SqlDataSource>, but you want to update a custom class, so you need to use <asp:ObjectDataSource> instead. Use the approach in this article, except with ObjectDataSource instead of SqlDataSource.
But first you have to make your model (i.e., Class1) compatible with ObjectDataSource by marking it with [System.ComponentModel.DataObject] and designating the appropriate update method like this:
[System.ComponentModel.DataObjectMethodAttribute(
System.ComponentModel.DataObjectMethodType.Update, true)]
public bool UpdateProduct(string productName, ...) {
...
}
This would allow you to use an ObjectDataSource on your webform and finally get nice 2-way databinding. Read the links to for full details.
Visual Studio offers various clunky ways of automating this, such as TableAdapters and the infamous Strongly-Typed DataSet (STD), but those don't help people like yourself who have their own object model. I don't recommend STDs anyway.
I was thinking there was a better way?
I don't think your current approach is bad. If you're worried about having tons of logic in your webforms, you would gain much more by using an MVC approach than worrying about binding sugar...
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