C#

SqlConnection con;
string strSql;
SqlDataAdapter da;
DataTable dt;
SqlCommandBuilder cb;
BindingSource bs = null;

void PopulateDgv()
{
    LineID = new DataGridViewTextBoxColumn();
    QuoteID = new DataGridViewTextBoxColumn();
    ItemID = new DataGridViewComboBoxColumn();
    LookupItems = new DataGridViewButtonColumn();
    Quantity = new DataGridViewTextBoxColumn();
    UnitPrice = new DataGridViewTextBoxColumn();
    LineTotal = new DataGridViewTextBoxColumn();

    dgvItems.Columns.Clear();
    dgvItems.DataSource = null;
    dgvItems.Columns.AddRange(new DataGridViewColumn[] {LineID, QuoteID, ItemID, LookupItems, Quantity, UnitPrice, LineTotal });
    LineID.Name = "LineID";
    LineID.DataPropertyName = "LineID";
    LineID.Visible = false;
    QuoteID.Name = "QuoteID";
    QuoteID.DataPropertyName = "QuoteID";
    QuoteID.Visible = false;
    ItemID.Name = "ItemID";
    ItemID.DataPropertyName = "ItemID";
    LookupItems.Name = "LookupItems";
    LookupItems.DataPropertyName = "LookupItems";
    LookupItems.DefaultCellStyle.NullValue = "...";
    LookupItems.Resizable = DataGridViewTriState.False;
    Quantity.Name = "Quantity";
    Quantity.DataPropertyName = "Quantity";
    UnitPrice.Name = "UnitPrice";
    UnitPrice.DataPropertyName = "UnitPrice";
    LineTotal.Name = "LineTotal";
    LineTotal.DataPropertyName = "LineTotal";
    LineTotal.ReadOnly = true;

    BindDGVComboBox(ItemID, "Select ItemID,Item From tblShopItems Order By ItemID", "ItemID", "Item");

    if (bs == null) { bs = new BindingSource(); }
    if (dt == null) { dt = new DataTable(); }
    strSql = "Select LineID,QuoteID,ItemID,'...' As LookupItems,Quantity,UnitPrice,LineTotal From tblShopQuotesItems Where QuoteID=" + Globals.Val(Tag);
    da = CreateDataAdapter(strSql);
    cb = new SqlCommandBuilder(da);
    dt.Locale = System.Globalization.CultureInfo.InvariantCulture;
    dt.Clear();
    da.Fill(dt);
    bs.DataSource = dt;
    dgvItems.DataSource = bs;
}

void BindDGVComboBox(DataGridViewComboBoxColumn objComboBox, string strQuery, string strValueMember, string strDisplayMember)
{
    DataSet ds = new DataSet();

    ds = CreateDataSet(strQuery);
    DataView dv = ds.Tables["dtDataTable"].DefaultView;
    objComboBox.DataSource = null;
    objComboBox.DataSource = dv;
    if (strValueMember != null) { objComboBox.ValueMember = strValueMember; }
    objComboBox.DisplayMember = strDisplayMember;
}

DataSet CreateDataSet(string strQuery)
{
    DataSet ds = new DataSet();
    SqlDataAdapter da = CreateDataAdapter(strQuery);
    SqlCommandBuilder cb = new SqlCommandBuilder(da);
    da.Fill(ds, "dtDataTable");
    return ds;
}

SqlDataAdapter CreateDataAdapter(string strQuery)
{
    SetConnection();
    SqlDataAdapter daAdapter = new SqlDataAdapter(strQuery, con);
    CloseConnection();
    return daAdapter;
}

void SetConnection()
{
    if (con == null) { con = new SqlConnection(GetConnectionString()); }
    if (con.State == ConnectionState.Closed) { con.Open(); }
}

string GetConnectionString()
{
    string strConn;
    strConn = "Persist Security Info=False;User ID=sa;Password=;Initial Catalog=TestDB;Data Source=MyServer";
    return strConn;
}