When I run the following code I get:
Cast from type 'DBNull' to type 'Date' is not valid.

The datatype for the field is smalldatetime.
I can run it fine from SQL Server

Dim strSQL As String
strSQL = "SELECT MIN(ESDate) AS MinDate, MAX(EFDate) AS MaxDate FROM P3ActWBS WHERE "
strSQL &= "WBSNumber = '" & strWBSN & "'"
Dim cmd2 As New SqlCommand(strSQL, sCon1)
Dim DR2 As SqlDataReader = cmd2.ExecuteReader()
DR2.Read()
If DR2.HasRows = True Then

Dim strMinDate As Date = DR2(0)
Dim strMaxDate As Date = DR2(1)
DR2.Close()
DR2 = Nothing