Delete ASP.Net DropDownList items on Button Click and display updated items after login using C# and VB.Net

Hi KatieNgoc,

According to your requirement you need to create a table where you have to store user login detail and delete DropDownList data. And then get data from table according to user login, after that you have to check whether inserted data and your DropDownList data are same if same then have to delete.

Check below code.

HTML

Login.aspx

Name :
<asp:TextBox runat="server" ID="txtName" />
<br />
<asp:Button Text="Loging" runat="server" OnClick="Loginn" />

CS.aspx

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

Namespaces

C#

using System.Data;
using System.Configuration;
using System.Data.SqlClient;

VB.Net

Imports System.Data
Imports System.Data.SqlClient

Code

Login.aspx.cs

protected void Loginn(object sender, EventArgs e)
{
    Session["UserName"] = txtName.Text;
    Response.Redirect("CS.aspx");
}

Login.aspc.vb

Protected Sub Loginn(ByVal sender As Object, ByVal e As EventArgs)
    Session("UserName") = txtName.Text
    Response.Redirect("CS.aspx")
End Sub

CS.aspx.cs

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        if (Session["ListItems"] == null)
        {
            DataTable dt = DropDownItems();
            string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
            SqlConnection con = new SqlConnection(constr);
            SqlCommand cmd = new SqlCommand("SELECT * FROM UserDetail WHERE UserDetail = @User", con);
            cmd.Parameters.AddWithValue("@User", Session["UserName"].ToString());
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataTable dt1 = new DataTable();
            da.Fill(dt1);
            if (dt1.Rows.Count > 0)
            {
                for (int i = 0; i < dt.Rows.Count; i++)
                {
                    for (int j = 0; j < dt1.Rows.Count; j++)
                    {
                        if (dt.Rows[i]["Text"].ToString() == dt1.Rows[j]["SelectedText"].ToString())
                        {
                            dt.Rows[i].Delete();
                        }
                    }
                }
            }
            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)
        {
            dt.Rows[i].Delete();
            string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
            SqlConnection con = new SqlConnection(constr);
            SqlCommand cmd = new SqlCommand("INSERT INTO UserDetail VALUES(@SelectedText,@SelectedVal,@UserName)", con);
            cmd.Parameters.AddWithValue("@SelectedText", li.Text);
            cmd.Parameters.AddWithValue("@SelectedVal", li.Value);
            cmd.Parameters.AddWithValue("@UserName", Session["UserName"].ToString());
            con.Open();
            cmd.ExecuteNonQuery();
            con.Close();
        }
    }
    Session["ListItem"] = dt;
    DropDownList1.DataSource = dt;
    DropDownList1.DataTextField = "Text";
    DropDownList1.DataValueField = "Value";
    DropDownList1.DataBind();
}

VB.Net

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()
            Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
            Dim con As SqlConnection = New SqlConnection(constr)
            Dim cmd As SqlCommand = New SqlCommand("SELECT * FROM UserDetail WHERE UserDetail = @User", con)
            cmd.Parameters.AddWithValue("@User", Session("UserName").ToString())
            Dim da As SqlDataAdapter = New SqlDataAdapter(cmd)
            Dim dt1 As DataTable = New DataTable()
            da.Fill(dt1)
            If dt1.Rows.Count > 0 Then
                For i As Integer = 0 To dt.Rows.Count - 1
                    For j As Integer = 0 To dt1.Rows.Count - 1
                        If dt.Rows(i)("Text").ToString() = dt1.Rows(j)("SelectedText").ToString() Then
                            dt.Rows(i).Delete()
                        End If
                    Next
                Next
            End If
            DropDownList1.DataSource = dt
            DropDownList1.DataTextField = "Text"
            DropDownList1.DataValueField = "Value"
            DropDownList1.DataBind()
            Session("ListItems") = dt
        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()
            Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
            Dim con As SqlConnection = New SqlConnection(constr)
            Dim cmd As SqlCommand = New SqlCommand("INSERT INTO UserDetail VALUES(@SelectedText,@SelectedVal,@UserName)", con)
            cmd.Parameters.AddWithValue("@SelectedText", li.Text)
            cmd.Parameters.AddWithValue("@SelectedVal", li.Value)
            cmd.Parameters.AddWithValue("@UserName", Session("UserName").ToString())
            con.Open()
            cmd.ExecuteNonQuery()
            con.Close()
        End If
    Next

    Session("ListItem") = dt
    DropDownList1.DataSource = dt
    DropDownList1.DataTextField = "Text"
    DropDownList1.DataValueField = "Value"
    DropDownList1.DataBind()
End Sub