Find min/max datetime in datatable rows

Question

I have a data table that contains a "CreateDate" and an "UpdateDate" columns. I am trying to find the smallest CreateDate and largest UpdateDate. It is not difficult but columns can contain NULL (or DBNull) and this is tripping me. I was using the following:

DateTime dtMin = DateTime.MaxValue;
DateTime dtMax = DateTime.MinValue;

foreach(DataRow dr in dt.Rows)
{
    DateTime dtCreateDate = dr.Field<DateTime>("CreateDate");
    DateTime dtUpdateDate = dr.Field<DateTime>("UpdateDate");
    dtMin = dtMin > dtCreateDate ? dtCreateDate : dtMin;
    dtMax = dtMax > dtUpdateDate ? dtMax : dtUpdateDate;
}

Until I hit a row with a NULL date.

Willy David Jr · Answer 1 · 2017-05-17T02:17:09.777

0

Check first if the value on the datarow is null before proceeding:

foreach (DataRow dr in dt.Rows)
     {
       if (dr["CreateDate"] != null && dr["UpdateDate"] != null)
         {
           //TODO: Logic here
         }
     }

edited May 17 '17 at 02:17

answered May 17 '17 at 02:10

Willy David Jr

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Hieu Le · Accepted Answer · 2017-05-17T04:53:17.230

You should to check DBNull.Value and null before you parse values to DateTime because DateTime datetype cannot contain null values. Remember that DBNull.Value and object null are 2 different things

By declaring DateTime?, dtCreateDate, dtUpdateDate can contain null value. Then, if you receive a null value, you can skip to compare it with dtMin and dtMax.

foreach (DataRow dr in dt.Rows)
{
    DateTime? dtCreateDate = dr["CreateDate"] == DBNull.Value || dr["CreateDate"] == null ? (DateTime?) null : dr.Field<DateTime>("CreateDate");
    DateTime? dtUpdateDate = dr["UpdateDate"] == DBNull.Value || dr["UpdateDate"] == null ? (DateTime?) null: dr.Field<DateTime>("UpdateDate");


    dtMin = dtCreateDate == null ? dtMin : (dtMin > dtCreateDate ? dtCreateDate : dtMin);
    dtMax = dtUpdateDate == null ? dtMax : (dtMax > dtUpdateDate ? dtMax : dtUpdateDate);

}

I thought about this, but if in first iteration I found a valid dtCraeteDate and in the next iteration I get a NULL date to compare, I don't want to set dtCreatDate back to DateTime.MinValue. — NoBullMan, May 17 '17 at 02:24
I updated my suggestion. Declare DateTime? which allow you to contain null value — Hieu Le, May 17 '17 at 02:31

score 0 · Answer 3 · edited May 23 '17 at 12:34

0

You can use Min & Max compute that are supported by data tables. Other option is to use LINQ to find min & max. For reference please see answer on following link. How to select min and max values of a column in a datatable?

edited May 23 '17 at 12:34

Community

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answered May 17 '17 at 02:30

Muhammad Awais

26
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score 0 · Answer 4 · answered May 17 '17 at 03:01

This map help you

foreach (DataRow dr in dt.Rows)
{
    DateTime? dtCreateDate = (DateTime?)dr["CreateDate"];
    DateTime? dtUpdateDate = (DateTime?)dr["UpdateDate"];
    dtMin = (dtCreateDate != null && dtMin > dtCreateDate) ? dtCreateDate.Value : dtMin;
    dtMax = (dtUpdateDate != null && dtMax < dtUpdateDate) ? dtUpdateDate.Value : dtMax;
}

score 0 · Answer 5 · answered May 17 '17 at 05:15

Here use coalescing operator and conditional operator ,for managing the conditions :

foreach (DataRow dr in dt.Rows)
{
    // Collecting data from DataRow
    DateTime? dtCreateDate =dr.Field<DateTime?>("CreateDate")??(DateTime?)null;
    DateTime? dtUpdateDate=dr.Field<DateTime?>("UpdateDate")??(DateTime?)null;

    // Manupulating condition to get required result
    dtMin = dtCreateDate != null ?(dtMin > dtCreateDate ? dtCreateDate : dtMin) : dtMin;
    dtMax = dtUpdateDate != null ?(dtMax > dtUpdateDate ? dtMax : dtUpdateDate): dtMax;
}

Find min/max datetime in datatable rows

5 Answers5