When inserting data into Oracle, how to handle the time null value read by Excel

If the time value read from Excel is a null value, do the following conversions

String YDKGSJ = String. Empty;
if (dbdata. Rows[i]["agreed to start time"]. ToString () = = "")
{
YDKGSJ = "null,";
}
Else
{
YDKGSJ = "To_date ('" + convert.todatetime (dbdata). Rows[i]["agreed to start time"]) + "', ' yyyy-mm-dd HH24:MI:SS '),";
}

When reading Excel data, convert to fields that are not string types, and pay attention to the null value type!!!!

such as double type

Total cost of allocated land
Double TDJK = 0;
if (dbdata. rows[i]["Total cost of land appropriated"]. ToString () = = "")
{
TDJK = 0;
}
Else
{
TDJK = Convert.todouble (dbdata. rows[i]["Total cost of appropriated land"]);
}

When inserting data into Oracle, how to handle the time null value read by Excel