VB.net droplist

Question

User1298215938 posted

Hi, I'm new to asp.net how do remove items from another droplist if valve equals to 33105?

Dim Plant(2) As String
Dim strplant As String
Plant(0) = "N/A"
Plant(1) = "33105"

Array.Reverse(Plant)

For Each strplant In Plant
plantlist.Items.Add(strplant)
Next

Dim area(2) As String
Dim strarea As String
area(0) = "666"
area(1) = "777"

Array.Reverse(area)

For Each strarea In area
Arealist.Items.Add(strarea)
Next

If plantlist.SelectedIndex = 1 Then
Arealist.Visible = "True"
End If

Answer 1

User-1330468790 posted

Hi MOHIIMRAN,

 

It looks like you want to use the event "OnSelectedIndexChanged" of the drop down list, which would be called when the selected item is changed. Bear in mind that you could turn on the "autopostback" flag so that the post will be triggered automatically when the selected item changes.

 

You could refer to below codes to see if it explains how to implement the function you desired.

ASPX

 <div>
            <asp:DropDownList ID="plantlist" runat="server" OnSelectedIndexChanged="plantlist_SelectedIndexChanged" AutoPostBack="true"></asp:DropDownList>
            <asp:DropDownList ID="Arealist" runat="server"></asp:DropDownList>
        </div>

Code behind:

 Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If Not IsPostBack Then
            InitDDLs()
        End If
    End Sub

    Private Sub InitDDLs()
        Dim Plant As String() = New String(1) {}
        Plant(0) = "N/A"
        Plant(1) = "33105"
        // Here I removed the code line: Array.Reverse(Plant)
        //so that the default value of the drop down list will be "N/A"

        For Each strplant As String In Plant
            plantlist.Items.Add(strplant)
        Next

        Dim area As String() = New String(1) {}
        area(0) = "666"
        area(1) = "777"
        Array.Reverse(area)

        For Each strarea As String In area
            Arealist.Items.Add(strarea)
        Next

        If plantlist.SelectedIndex = 1 Then
            Arealist.Visible = True
        End If
    End Sub

    Protected Sub plantlist_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
        If plantlist.SelectedValue = "33105" Then
            Arealist.Items.Clear()
        Else
            Dim area As String() = New String(1) {}
            area(0) = "666"
            area(1) = "777"
            Array.Reverse(area)

            For Each strarea As String In area
                Arealist.Items.Add(strarea)
            Next
        End If
    End Sub

Demo:

 

Best regards,

Sean

Answer 2

User1298215938 posted

thank you so much sean how can i write if plant = 3105 than to hide area 666?

Answer 3

User-1330468790 posted

Hi MOHIIMRAN,

 

Simply make a modification on the method "plantlist_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)" as below:

Protected Sub plantlist_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
        If plantlist.SelectedValue = "33105" Then
            Arealist.Items.Remove("666")
        Else
            Dim area As String() = New String(1) {}
            area(0) = "666"
            area(1) = "777"
            Array.Reverse(area)
            Arealist.Items.Clear()
            For Each strarea As String In area
                Arealist.Items.Add(strarea)
            Next
        End If
    End Sub

Demo:

 

However, if you have your own logic to bind the drop down list, you might need to consider change the code to fit your scenario.

 

Best regards,

Sean

Answer 4

User1298215938 posted

thanks sean