how to find the max in a datacolumn of datetime?

Question

I have a DataColumn of DateTime, I would like to know how I can have only the sooner date (min) and the later date (max).

Thanks

Answer 1

This would give what you are looking for:

// Initial Code for Testing
DataTable dt = new DataTable();

dt.Columns.Add("Dates", typeof(DateTime));
dt.Rows.Add(new object[] { DateTime.Now });
dt.Rows.Add(new object[] { DateTime.Now.AddDays(1) });
dt.Rows.Add(new object[] { DateTime.Now.AddDays(2) });

This is the code you would use:

// Actual Code
DataColumn col = dt.Columns[0]; // Call this the one you have

DataTable tbl = col.Table;

var first = tbl.AsEnumerable()
               .Select(cols => cols.Field<DateTime>(col.ColumnName))
               .OrderBy(p => p.Ticks)
               .FirstOrDefault();

var last = tbl.AsEnumerable()
              .Select(cols => cols.Field<DateTime>(col.ColumnName))
              .OrderByDescending(p => p.Ticks)
              .FirstOrDefault();

Answer 2

object maxDate = dataTable.Compute("MAX(TheDateColumnName)", null);
object minDate = dataTable.Compute("MIN(TheDateColumnName)", null);

Answer 3

To add to the answer from kyle, isn't it easier to just do:

for greatest date:

var last = tbl.AsEnumerable()
               .Max(r => r.Field<DateTime>(col.ColumnName));

and for earliestdate:

var first = tbl.AsEnumerable()
               .Min(r => r.Field<DateTime>(col.ColumnName));

Answer 4

Just retreive a List of DateTime from your DataColumn, Foreach row in your DataColumn add the current element to your List of DateTime.

List<DateTime> and use Sort method then get the first and the last values.

Depending of your framework version, for 2.0 use above, for >=3.5 you can use Max and Min or With linq .OrderByDesc(p => p.X).FirstOrDefault(); on your DateTime List

Answer 5

DataTable dt = new DataTable("MyDataTable");
DataColumn dc = new DataColumn("DateColumn");
dc.DataType = typeof(DateTime);
dt.Columns.Add(dc);
for (int i = 0; i <= 5; i++)
{
    DataRow newRow = dt.NewRow();
    newRow[0] = DateTime.Now.AddDays(i);
    dt.Rows.Add(newRow);
}

DateTime maxDate =  
    Convert.ToDateTime(
                        ((from DataRow dr in dt.Rows
                          orderby Convert.ToDateTime(dr["DateColumn"]) descending
                          select dr).FirstOrDefault()["DateColumn"]
                          )
                        );

DateTime minDate = 
    Convert.ToDateTime(
                        ((from DataRow dr in dt.Rows
                          orderby Convert.ToDateTime(dr["DateColumn"]) ascending
                          select dr).FirstOrDefault()["DateColumn"]
                          )
                        );

Answer 6

Simpliest for me: make a dataset with a Table "Tablename" and a column "itemDate" ,set Datatyp System.DateTime

you can read all elements in a list of datetime and search for minDate

Dim List_Date As New List(Of DateTime)
Dim minDate As DateTime

For Each elem As DataRow In DataSet1.Tables("Tablename").Rows
            List_Date.Add(elem.Item("itemDate"))
Next

minDate = List_Date.Min