Howto Insert A Null DateTime Into A Sql Server 2005 Database

I'm importing data form an Excel file to a Sql Server Database. Some of the data imported represents time as a double type so i convert the times into DateTime to be inserted into the database. The time values that aren't available in the Excel file are 0.. so what i want to do is insert null into the database for all the values that are 0 in the excel file... How do i do that based on this code i have so far:protected void ButtonImport_Click(object sender, EventArgs e)
{PanelUpload.Visible = false;
PanelView.Visible = false;PanelImport.Visible = true;
LabelImport.Text = "";OleDbCommand objCommand = new OleDbCommand();
objCommand = ExcelConnection();
 OleDbDataReader reader;
reader = objCommand.ExecuteReader();
 while (reader.Read())
{DateTime? in_1 = null;
DateTime? out_1 = null;DateTime? in_2 = null;DateTime? out_2 = null;
 
 
 int emp_id = Convert.ToInt32(reader["emp_id"]);
DateTime date_entry = Convert.ToDateTime(reader["date_entry"]);if (Convert.ToDouble(reader["in_1"]) != 0)
in_1 = ConvertDoubleToDateTime((double)reader["in_1"]);if (Convert.ToDouble(reader["out_1"]) != 0)
out_1 = ConvertDoubleToDateTime((double)reader["out_1"]);if (Convert.ToDouble(reader["in_2"]) != 0)
in_2 = ConvertDoubleToDateTime((double)reader["in_2"]);if (Convert.ToDouble(reader["out_2"]) != 0)
out_2 = ConvertDoubleToDateTime((double)reader["out_2"]);
 
ImportIntoAttendance(emp_id, date_entry, in_1, out_1, in_2, out_2);
}
 
reader.Close();
}protected void ImportIntoAttendance(int emp_id, DateTime date_entry, DateTime? in_1, DateTime? out_1, DateTime? in_2, DateTime? out_2)
{
 SqlDataSource AttendanceDataSource = new SqlDataSource();
AttendanceDataSource.ConnectionString = ConfigurationManager.ConnectionStrings["SalariesConnectionString1"].ToString();AttendanceDataSource.InsertCommandType = SqlDataSourceCommandType.Text;
AttendanceDataSource.InsertCommand = "INSERT INTO Attendance (emp_id, date_entry, in_1, out_1, in_2, out_2) " +"VALUES ('" + emp_id + "', '" + date_entry + "', '" + in_1 + "', '" + out_1 + "', " +"'" + in_2 + "', '" + out_2 + "')";
 
int rowsAffected = 0;
try
{
rowsAffected = AttendanceDataSource.Insert();
}catch(Exception ex)
{LabelImport.Text += "<font color=red>" + ex + "</font><br />";
}
 
}private DateTime ConvertDoubleToDateTime(double dbTime)
{string[] SplitTime = dbTime.ToString().Split('.');
string hours = SplitTime[0];string minutes = String.Empty;string time = String.Empty;
 if (dbTime.ToString().IndexOf('.') != -1)
{if (SplitTime[1].Length >= 1)
{
if (SplitTime[1].Length == 1)minutes = Convert.ToString(Convert.ToDouble(SplitTime[1]) * 10);else if (SplitTime[1].Length > 1)
minutes = SplitTime[1];
}
}
elseminutes = "00";
time = hours + ":" + minutes;return Convert.ToDateTime(time);
}