Question

似乎是一个微不足道的问题，但无法确定解决方案。

我有一个数据表的下拉列表。我正在尝试在位置0插入一个新项目，但是当加载控件时，我没有看到新的列表项或任何错误。

Public Sub Page_Load(ByVal sender As Object, ByVal e As eventargs) Handles Me.Load
    If Not Page.IsPostBack Then
        loadRegistrantAbstracts()
    End If
End Sub
Public Sub loadRegistrantAbstracts()
    Dim obj As New Lookups
    Dim dtAbstracts As DataTable

    dtAbstracts = obj.getAbstracts()

    If dtAbstracts.Rows.Count > 0 Then
        With ddlAbstracts
            .DataSource = dtAbstracts
            .DataTextField = "DisplayName"
            .DataValueField = "AbstractID"
            .DataBind()
            .Items.Insert(0, New ListItem("Select Abstract..", "0"))
        End With
    End If
End Sub

Answer 1

由于DropDownList被绑定，它将呈现DataTable中的“stuff”。您需要在DataTable中将“Select Abstract ...”选项添加为DataRow。当您更改.DataSource的源时，它将反映在DropDownList中。

您很可能是从数据库加载此内容，因此您可能决定在查询中包含“选择...”选项：

SELECT 0 AS id, 'Select Abstract ...' AS abstract_name, 0 AS sort_order
UNION
SELECT dbo.abstracts.id, dbo.abstracts.name AS abstract_name, 1 as sort_order FROM dbo.abstracts
ORDER BY sort_order, abstract_name

Answer 2

答案，部分归功于HardCode，如下：

Public Sub Page_Load(ByVal sender As Object, ByVal e As eventargs) Handles Me.Load
    If Not Page.IsPostBack Then
        loadRegistrantAbstracts()
    End If
End Sub
Public Sub loadRegistrantAbstracts()
    Dim obj As New Lookups
    Dim dtAbstracts As DataTable

    dtAbstracts = obj.getAbstracts()

    Dim row As DataRow = dtAbstracts.NewRow

    row("DisplayName") = "Select Abstract..."
    row("AbstractID") = "0"

    dtAbstracts.Rows.InsertAt(row, 0)

    If dtAbstracts.Rows.Count > 0 Then
        With ddlAbstracts
            .DataSource = dtAbstracts
            .DataTextField = "DisplayName"
            .DataValueField = "AbstractID"
            .DataBind()
        End With
    End If
End Sub

将项目插入下拉列表时出现问题

2 个答案: