how to write select parameterized query in asp.net

Below code is written to call parameterized select query in asp.net

public bool checkConflictTime()
{
    bool TimeExists = false;

    DataSet ds = new D开发者_如何学PythonataSet();

    SqlConnection sqlconn = new SqlConnection();
    sqlconn.ConnectionString = ConfigurationManager.ConnectionStrings["TestConn"].ConnectionString;
    string sql = @"SELECT * FROM Images WHERE starttime= @starttime AND endtime = @endtime";

    SqlCommand sqlcommand = new SqlCommand(sql,sqlconn);

    //sqlcommand.Connection = sqlconn;

    //string sql = "CheckConflictTimings";


    sqlcommand.CommandType = CommandType.Text;
    sqlcommand.CommandText = sql;

    sqlcommand.Parameters.Add(new SqlParameter("@starttime", ddlStartTime.SelectedItem.Text));
    sqlcommand.Parameters.Add(new SqlParameter("@endtime", ddlEndTime.SelectedItem.Text));

    SqlDataAdapter da = new SqlDataAdapter(sql, sqlconn);
    try
    {
        da.Fill(ds);
        if (ds.Tables[0].Rows.Count > 0)
        {
            TimeExists = true;
        }
    }   
    catch (Exception ex)
    {

    }
    finally
    {
        sqlconn.Close();
        sqlconn.Dispose();  
    }
    return TimeExists;
}

Is there something wrong? it threw error of :Must declare the scalar variable "@starttime" when filling data adapter.

---

Try

SqlDataAdapter da = new SqlDataAdapter(sqlcommand);

---

Try

sqlcommand.Parameters.Add(new SqlParameter("starttime", ddlStartTime.SelectedItem.Text));

I don't think you need the @ prefix when adding the parameter.

---

I think you're not passing your command as a SelectCommand to the adapter.

da.SelectCommand = sqlcommand;

---

Try

  sqlcommand.Parameters.AddWithValue("@starttime",ddlStartTime.SelectedItem.Text);

instead of

   sqlcommand.Parameters.Add(new SqlParameter("@starttime", ddlStartTime.SelectedItem.Text));