查找SQL OleDbDataReader的长度

Question

I have an SQL OleDbDataReader taking data from access into my visual basic front end. Is it possible to find the number of records the reader is holding? As i would like to use this value to end a loop.

Below is my code. This part of it is for finding data to run a calculation and insert the value back into access. I am currently using a batch method because i had time out errors stating that the code was taking too long when calculating all data points for a calculation at once. The code below works for the first batch but fails on the second as it can't look at the next section of data within the reader. The data may not be in the correct order within the reader in future so looking at all of the reader at once is the best solution. To fix this issue I need to make Do Until SearchCounter = the length of the reader . I tried putting the contents of the reader into an array to find its length however this was very time consuming. Any other suggestions would be very welcome.

For CalcParameterCounter = 0 To CalcParams.GetLength(0) - 1

                ParamQuery = "ID_PAR = " & Format(CalcParams(CalcParameterCounter), "0")
                conditions = ParamQuery ' & UploadQuery

                DatabaseConnection("SELECT " & FieldNames & " FROM " & tablename & " WHERE " & conditions, "Read Recordset"

                CalcDataRecordPointer = 0
                Do Until rdrOLEDB.Read = False
                    SearchCounter = 0
                    Do Until SearchCounter = CalcData.GetLength(1)
                        CalcDataRecordPointer = CalcDataRecordPointer + 1
                        If CalcDataRecordPointer = CalcData.GetLength(1) Then CalcDataRecordPointer = 0
                        Value = rdrOLEDB.Item(1)
                        If CDate(rdrOLEDB.Item(0).ToString()) = CDate(CalcData(0, CalcDataRecordPointer)) Then
                            match = True
                            CalcData(CalcParameterCounter + 1, CalcDataRecordPointer) = rdrOLEDB.Item(1).ToString()
                            Exit Do
                        Else
                            match = False
                        End If
                        SearchCounter = SearchCounter + 1
                    Loop
                Loop
                'Close:
                rdrOLEDB.Close()
                cnnOLEDB.Close()
            Next

Answer 1

Using the reader.Read() is the documented method for looping through a recordset. I've done some programming in VBA and ADO where by a different cursor type will give you the total number of records before you loop through them. This does create a performance hit, namely because of the I was using Excel, and the fact that the command object has to put the recordset into memory first before the reader starts.

Although OleDb is perfectly acceptable data library, maybe look at ADO to perform the same job, which is compatible (as of MDAC2.8) SQL 2000 -> 2008 R2. Another way to look at this problem would be to see if you could do the processing in a SQL Stored Procedure, then output it to your code.

Good Luck.