string leavefrom = datepicker1.Text;
    DateTime lFrom = Convert.ToDateTime(leavefrom);

    string leaveto = datepicker2.Text;
    DateTime lTo = Convert.ToDateTime(leaveto);

    string sqlquery = "insert into Leave (EmployeeId,Leavetype,LeaveFrom,LeaveTo,LeaveDescription,LeaveStatus) values (@Id,@Ltype,@Leavefrom,@Leaveto,@LeaveDesc,@LStatus)";


    using (SqlConnection conn = new SqlConnection("Data Source=USER-PC;Initial Catalog=1GCAttendanceManagementSystem;Integrated Security=True"))
    {
        using (SqlCommand cmd = new SqlCommand(sqlquery, conn))
        {
            cmd.Parameters.Add("@Id", SqlDbType.VarChar).Value = txtCode.Text;
            cmd.Parameters.Add("@Ltype", SqlDbType.VarChar).Value = DropDownListType.Text;

            cmd.Parameters.Add("@Leavefrom", SqlDbType.Date).Value = lFrom;
            cmd.Parameters.Add("@Leaveto", SqlDbType.Date).Value = lTo;

            cmd.Parameters.Add("@LeaveDesc", SqlDbType.VarChar).Value = txtDescription.Text;
            cmd.Parameters.Add("@LStatus", SqlDbType.VarChar).Value = txtStatus.Text;
            conn.Open();
            cmd.ExecuteNonQuery();
        }
    }