Remove item from DropDownList on Button Click and rebind on Page Load using C# and VB.Net in ASP.Net

KatieNgo...

SOLVED CLOSED ACTIVE ANSWERED
User: KatieNgoc
Posted: on Jun 30, 2019 11:58 PM
Forum: ASP.Net Web Forms
Answer: 1
Views: 5390
Sample Code: Download

Hello,

I have 2 webpages: Default.aspx and Next.aspx

Default page has a content with 2 objects: dropdownlist box and button

Next page has a content with 1 button object (link to default page)

The ideas: When I visit the 1st page (Default), it shows a list of 4 items. If I click on button object, it will delete 1 selected item and go to 2nd page( Next.aspx ). From here, I click on button, it links back to 1 st page.I got an emty list after I visit it back.

How can I have:

The 1st page should be displayed only 3 items remaining on its lists, if I select 1 item on the list, it will be deleted and link to 3rd page(test.aspx).

Next visit, it will display 2 until it's done (empty list)

Here are the codes: (Please help. Thank you so much)

1stpage content:

<asp:Content ID="BodyContent" ContentPlaceHolderID="MainContent" runat="server">
<asp:DropDownList ID="DropDownList1" runat="server"></asp:DropDownList>
<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" /></asp:Content>

C# for 1st page:

namespace DropdownListSession
{
    public partial class _Default : Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!this.IsPostBack)
            {
                if (Session["ListItems"] == null)
                {
                    DataTable dt = DropDownItems();
                    DropDownList1.DataSource = dt;
                    DropDownList1.DataTextField = "Text";
                    DropDownList1.DataValueField = "Value";
                    DropDownList1.DataBind(); Session["ListItems"] = dt;

                }

            }
        }
        private DataTable DropDownItems()
        {
            DataTable dt = new DataTable();
            dt.Columns.Add("Text");
            dt.Columns.Add("Value");
            dt.Rows.Add("Item1", "1");
            dt.Rows.Add("Item2", "2");
            dt.Rows.Add("Item3", "3");
            dt.Rows.Add("Item4", "4");
            return dt;
        }
        protected void Button1_Click(object sender, EventArgs e)
        {
            DataTable dt = Session["ListItems"] as DataTable;
            ListItemCollection liCol = DropDownList1.Items;
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                ListItem li = liCol[i]; if (li.Selected)
                {
                    Response.Redirect("Next.aspx"); dt.Rows[i].Delete();
                }
            }
            Session["ListItem"] = dt;
            DropDownList1.DataSource = dt;
            DropDownList1.DataTextField = "Text";
            DropDownList1.DataValueField = "Value";
            DropDownList1.DataBind();
        }
    }
}

2nd page content:

<asp:Content ID="Content1" ContentPlaceHolderID="MainContent" runat="server">
<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" /></asp:Content>

C# for 2nd page:

namespace DropdownListSession
{
    public partial class Next : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            Response.Redirect("Default.aspx");
        }
    }
}

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pandeyis...

0 2

Reply
ANSWER
User: pandeyism
Replied: on Jul 01, 2019 04:38 AM
Modified: on Jul 01, 2019 04:39 AM
Report

Hi KatieNgoc,

Refer below sample.

You need to rebind dropdownusing session data.

HTML

Default.aspx

<asp:DropDownList ID="DropDownList1" runat="server">
</asp:DropDownList>
<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />

Next.aspx

<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />

Code

Default.aspx.cs

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        if (Session["ListItems"] == null)
        {
            DataTable dt = DropDownItems();
            DropDownList1.DataSource = dt;
            DropDownList1.DataTextField = "Text";
            DropDownList1.DataValueField = "Value";
            DropDownList1.DataBind();
            Session["ListItems"] = dt;
        }
        else
        {
            DataTable dt = (DataTable)Session["ListItems"];
            DropDownList1.DataSource = dt;
            DropDownList1.DataTextField = "Text";
            DropDownList1.DataValueField = "Value";
            DropDownList1.DataBind();
        }
    }
}

private DataTable DropDownItems()
{
    DataTable dt = new DataTable();
    dt.Columns.Add("Text");
    dt.Columns.Add("Value");
    dt.Rows.Add("Item1", "1");
    dt.Rows.Add("Item2", "2");
    dt.Rows.Add("Item3", "3");
    dt.Rows.Add("Item4", "4");
    return dt;
}

protected void Button1_Click(object sender, EventArgs e)
{
    DataTable dt = Session["ListItems"] as DataTable;
    ListItemCollection liCol = DropDownList1.Items;
    for (int i = 0; i < dt.Rows.Count; i++)
    {
        ListItem li = liCol[i]; 
        if (li.Selected)
        {
            dt.Rows[i].Delete();
            Response.Redirect("Next.aspx"); 
        }
    }
}

Next.aspx

protected void Button1_Click(object sender, EventArgs e)
{
    Response.Redirect("Default.aspx");
}

VB.Net

Default.aspx.vb

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

            If Session("ListItems") Is Nothing Then
                Dim dt As DataTable = DropDownItems()
                DropDownList1.DataSource = dt
                DropDownList1.DataTextField = "Text"
                DropDownList1.DataValueField = "Value"
                DropDownList1.DataBind()
                Session("ListItems") = dt
            Else
                Dim dt As DataTable = CType(Session("ListItems"), DataTable)
                DropDownList1.DataSource = dt
                DropDownList1.DataTextField = "Text"
                DropDownList1.DataValueField = "Value"
                DropDownList1.DataBind()
            End If
        End If
    End Sub

    Private Function DropDownItems() As DataTable
        Dim dt As DataTable = New DataTable()
        dt.Columns.Add("Text")
        dt.Columns.Add("Value")
        dt.Rows.Add("Item1", "1")
        dt.Rows.Add("Item2", "2")
        dt.Rows.Add("Item3", "3")
        dt.Rows.Add("Item4", "4")
        Return dt
    End Function

    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)
        Dim dt As DataTable = TryCast(Session("ListItems"), DataTable)
        Dim liCol As ListItemCollection = DropDownList1.Items

        For i As Integer = 0 To dt.Rows.Count - 1
            Dim li As ListItem = liCol(i)

            If li.Selected Then
                dt.Rows(i).Delete()
                Response.Redirect("Next.aspx")
            End If
        Next
    End Sub

Next.aspx.vb

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)
    Response.Redirect("Default.aspx")
End Sub

Screenshot

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Remove item from DropDownList on Button Click and rebind on Page Load using C# and VB.Net in ASP.Net

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