Populate ASP.Net DroipDownList on TextBox Change using Business Class

Hi SUJAYS,

Please refer below sample.

HTML

<asp:TextBox ID="txtId" runat="server" AutoPostBack="true" OnTextChanged="BindDropdown"></asp:TextBox>
<asp:DropDownList ID="ddlCountry" runat="server">
</asp:DropDownList>

Namespaces

C#

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

VB.Net

Imports System.Data
Imports System.Data.SqlClient

Code

C#

BEL.cs

public class BEL
{
    private int _Id;
    public int id
    {
        get
        {
            return _Id;
        }
        set
        {
            _Id = value;
        }
    }
}

BLL.cs

public class BLL
{
    public DataTable GetData(BEL enities)
    {
        DAL dal = new DAL();
        return dal.Data(enities);
    }
}

DAL.cs

public DataTable Data(BEL enities)
{
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT Country FROM Customers WHERE CustomerId = @Id", con))
        {
            cmd.Parameters.AddWithValue("@Id", enities.id);
            using (SqlDataAdapter da = new SqlDataAdapter(cmd))
            {
                DataTable dt = new DataTable();
                da.Fill(dt);
                return dt;
            }
        }
    }
}

CS.aspx.cs

protected void BindDropdown(object sender, EventArgs e)
{
    BEL entity = new BEL();
    entity.id = Convert.ToInt32(txtId.Text);
    BLL bll = new BLL();
    DataTable dt = bll.GetData(entity);
    ddlCountry.DataSource = dt;
    ddlCountry.DataTextField = "Country";
    ddlCountry.DataValueField = "Country";
    ddlCountry.DataBind();
}

VB.Net

BELVB.vb

Private _Id As Integer
Public Property id As Integer
    Get
        Return _Id
    End Get
    Set(ByVal value As Integer)
        _Id = value
    End Set
End Property

BLLVB.vb

Public Function GetData(ByVal enities As BELVB) As DataTable
    Dim dal As DALVB = New DALVB()
    Return dal.Data(enities)
End Function

DALVB.vb

Public Function Data(ByVal enities As BELVB) As DataTable
    Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(constr)
        Using cmd As SqlCommand = New SqlCommand("SELECT Country FROM Customers WHERE CustomerId = @Id", con)
            cmd.Parameters.AddWithValue("@Id", enities.id)
            Using da As SqlDataAdapter = New SqlDataAdapter(cmd)
                Dim dt As DataTable = New DataTable()
                da.Fill(dt)
                Return dt
            End Using
        End Using
    End Using
End Function

VB.aspx.vb

Protected Sub BindDropdown(ByVal sender As Object, ByVal e As EventArgs)
    Dim entity As BELVB = New BELVB()
    entity.id = Convert.ToInt32(txtId.Text)
    Dim bll As BLLVB = New BLLVB()
    Dim dt As DataTable = bll.GetData(entity)
    ddlCountry.DataSource = dt
    ddlCountry.DataTextField = "Country"
    ddlCountry.DataValueField = "Country"
    ddlCountry.DataBind()
End Sub

Screenshot