Below code will help you
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
InstanceData = (DataSet)(Session["InstanceData"]);
id1.DataSource = InstanceData.tables[0];
id1.DataTextField = "DB";
id1.DataValueField = "DB";
id1.DataBind();
}
}
protected void Button1_Click(object sender, EventArgs e)
{
string DataBase = id1.SelectedValue;
}