如何选择已经从数据库返回的一个DropDownList的值 [英] How to select a value of a DropDownList that has been returned from a database

问题描述

我有一个网页更新表单，每一个控制是同桌的属性。它应该是这样的：
每当我从主（第一批）的DropDownList值，查询应运行让所有的字段（属性）和填充根据我选择的值的其他控件。

I have a web update form where every control is a property of the same table. It should work this way: Whenever I select a value from the main(the first) dropdownlist, a query should be run getting all of the fields(properties) and filling the other controls depending of the value I selected.

事件code：

Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) Handles DropDownList1.SelectedIndexChanged
        Dim objModel As New ModelDAO ' the data access class taht contains search method          
        Dim myobject = objModel.searchObject(DropDownList1.Text)                      
        TextBox1.Text = myobject.Property2
        DropDownList2.SelectedValue = myobject.Property3 'what's wrong here?
    End Sub

控件：

<asp:DropDownList ID="DropDownList1" runat="server" AppendDataBoundItems="True"
                    DataSourceID="SqlDataSource1" DataTextField="MODEL" DataValueField="MODEL"
                    AutoPostBack="true" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
                    <asp:ListItem Text="-Select-" Value="" />
                    </asp:DropDownList>
<asp:DropDownList ID="DropDownList2" runat="server">
                        <asp:ListItem Value="0">-Select-</asp:ListItem>
                        <asp:ListItem>EDS</asp:ListItem>
                        <asp:ListItem>BDS</asp:ListItem>                            
                    </asp:DropDownList>

它的工作原理，除了第二个DropDownList的，我不知道如何改变所选的值，我想这样的：

It works except the second DropDownList, I don't know how to change the selected value, I tried this:

DropDownList2.Text = myobject.Property3

和这样的：

DropDownList2.SelectedValue = myobject.Property3

但是，在这两种情况下dropdownlist2没有显示出选定的项目。

But in both cases dropdownlist2 shows no selected item.

请注意：由于textbox.text确实让我不认为搜索方法有什么问题，正确的价值，这就是为什么我没有张贴

NOTE: Since textbox.text does get the right value I don't think search method has any problem, that's why I'm not posting it.

推荐答案

它不工作的方式很遗憾。我给你伪code，因为我是一个C＃呃，但是这是我常做的：

It doesn't work that way unfortunately. I'll give you pseudocode since I'm a C#er, but this is how I normally do it:

Dim int i = 0
ForEach Item in DDL.Items
    If Item.Text = databaseResult
        DDL.SelectedIndex = i
        ExitLoop
    EndIf
    i = i + 1
EndForEach

下面是从下面的评论跟帖工作code：

Here is the working code from the comment thread below:

Dim i As Integer = 0 
For Each listitem In DropDownList1.Items 
    If DropDownList3.SelectedItem.Text = myobject.property Then 
        DropDownList3.SelectedIndex = i 
        Exit For 
    End If 
    i = i + 1 
Next

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