Hi ahmadsubuhanl...,

Please refer below sample.

Database

I have made use of the following table Customers with the schema as follows.

I have already inserted few records in the table.

You can download the database table SQL by clicking the download link below.

Download SQL file

HTML

<asp:GridView runat="server" ID="gvCustomers" AutoGenerateColumns="false" OnRowDataBound="gvCustomers_RowDataBound">
    <Columns>
        <asp:BoundField HeaderText="ID" DataField="CustomerId" />
        <asp:BoundField HeaderText="Name" DataField="Name" />
        <asp:TemplateField HeaderText="Country">
            <ItemTemplate>
                <asp:DropDownCheckBoxes runat="server" ID="ddlCountries" Width="150px" UseSelectAllNode="false">
                    <Style SelectBoxWidth="150" DropDownBoxBoxWidth="150" DropDownBoxBoxHeight="90" />
                </asp:DropDownCheckBoxes>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

Namespaces

C#

using System.Data;
using System.Configuration;
using System.Data.SqlClient;
using Saplin.Controls;

VB.Net

Imports System.Configuration
Imports System.Data
Imports System.Data.SqlClient
Imports Saplin.Controls

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        this.BindGrid();
    }
}

private void BindGrid()
{
    string conn = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(conn))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT CustomerId, Name, Country FROM Customers", con))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter(cmd))
            {
                using (DataTable dt = new DataTable())
                {
                    sda.Fill(dt);
                    gvCustomers.DataSource = dt;
                    gvCustomers.DataBind();
                }
            }
        }
    }
}

protected void gvCustomers_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        DropDownCheckBoxes ddlCountries = e.Row.FindControl("ddlCountries") as DropDownCheckBoxes;
        ddlCountries.Items.Clear();
        string conn = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(conn))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT CustomerId, Country FROM Customers", con))
            {
                using (SqlDataAdapter sda = new SqlDataAdapter(cmd))
                {
                    using (DataTable dt = new DataTable())
                    {
                        sda.Fill(dt);
                        foreach (DataRow dr in dt.Rows)
                        {
                            ddlCountries.Items.Add(new ListItem(dr["Country"].ToString(), dr["CustomerId"].ToString()));
                        }
                    }
                }
            }
        }
    }
}

VB.Net

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

Private Sub BindGrid()
    Dim conn As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(conn)
        Using cmd As SqlCommand = New SqlCommand("SELECT CustomerId, Name, Country FROM Customers", con)
            Using sda As SqlDataAdapter = New SqlDataAdapter(cmd)
                Using dt As DataTable = New DataTable()
                    sda.Fill(dt)
                    gvCustomers.DataSource = dt
                    gvCustomers.DataBind()
                End Using
            End Using
        End Using
    End Using
End Sub

Protected Sub gvCustomers_RowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
    If e.Row.RowType = DataControlRowType.DataRow Then
        Dim ddlCountries As DropDownCheckBoxes = TryCast(e.Row.FindControl("ddlCountries"), DropDownCheckBoxes)
        ddlCountries.Items.Clear()
        Dim conn As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
        Using con As SqlConnection = New SqlConnection(conn)
            Using cmd As SqlCommand = New SqlCommand("SELECT CustomerId, Country FROM Customers", con)
                Using sda As SqlDataAdapter = New SqlDataAdapter(cmd)
                    Using dt As DataTable = New DataTable()
                        sda.Fill(dt)
                        For Each dr As DataRow In dt.Rows
                            ddlCountries.Items.Add(New ListItem(dr("Country").ToString(), dr("CustomerId").ToString()))
                        Next
                    End Using
                End Using
            End Using
        End Using
    End If
End Sub

Screenshot