dropdownlit with unique data

First bind the dropdown list like this.

string strSQL = "";

      string strEquipementID = "";

      string Datetime = "";

SqlConnection sqlCon = null;

      sqlCon = new SqlConnection(ConfigurationManager.AppSettings["ConnectionString"].ToString());

     SqlCommand sqlCmd = new SqlCommand();

     SqlDataAdapter adpData = null;

    SqlDataReader sdrData = null;       

strSQL = "SELECT * from equipment";

        cboDatetime.Items.Clear(); // Id of dropdownlist

        cboDatetime.Items.Insert(0, "------- Select -------");

  sqlCmd.CommandText = strSQL;

        sdrData = sqlCmd.ExecuteReader();

        if (sdrData.HasRows)

         {

           if (sdrData.Read())

           {

              strEquipementID = sdrData["id "].ToString();

              Datetime =  sdrData["dtime "].ToString();

              cboDatetime.Items.Add(new ListItem(Datetime, strEquipementID));

            }

         }

sdrData.Close();

Now you have bind the dropdownlist with the daetime value

Use the following code to bind datagrid. Make the autopostback true for the dropdown list and put the following code in selectindexchange event

strSQL = "SELECT * from equipment where id = " + cboDatetime.SelectedValue +" ";

Now get the value in dataset and bind the datagrid