Binding List Controls dynamically using a single method

In ASP.Net, we have number of List Controls such as DropDownList, ListBox, CheckBoxLists, RadioButtonList and BulletedList which contains a list of items in key value pair. Sometimes, it is required to bind these types of controls with values from any Database table.

The following code exaplains how to bind a DropDownList with values from any Database table:

protected void Page_Load(object sender, EventArgs e)
{
        if (!Page.IsPostBack)
        {
            DataTable dt = GetKeyValuePair("TblStudents", "sname", "sid", "-SELECT-");
            DropDownList1.DataSource = dt;
            DropDownList1.DataTextField = "sname";
            DropDownList1.DataValueField = "sid";
            DropDownList1.DataBind();
        }
}

public DataTable GetKeyValuePair(string TableName, string KeyColumn, string ValueColumn, string DefaultValue)
{
        string query;
        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["sqlcon"].ToString());
        SqlDataAdapter sqlda;
        DataTable dt;
        query = "SELECT '" + DefaultValue + "' AS " + KeyColumn + " , '" + DefaultValue + "' AS " + ValueColumn + " FROM " + TableName + " UNION ";
        query += "SELECT " + KeyColumn + ", " + ValueColumn + " FROM " + TableName;
        sqlda = new SqlDataAdapter(query, con);
        dt = new DataTable();
        sqlda.Fill(dt);
        return dt;
}