Question

I’m trying to create a custom script in SSIS 2008 that will loop over the selected input columns and concatenate them so they can be used to create a SHA1 hash. I’m aware of the available custom components but I’m not able to install them on our system at work.

Whilst the example posed here appears to work fine http://www.sqlservercentral.com/articles/Integration+Services+(SSIS)/69766/ when I’ve tested this selected only a few and not all columns I get odd results. The script only seems to work if columns selected are in sequential order. Even when they are in order, after so many records or perhaps the next buffer different MD5 hashes are generated despite the rows being exactly the same throughout my test data.

I’ve tried to adapt the code from the previous link along with these articles but have had no joy thus far.
http://msdn.microsoft.com/en-us/library/ms136020.aspx
http://agilebi.com/jwelch/2007/06/03/xml-transformations-part-2/

As a starting point this works fine to display the column names that I have selected to be used as inputs

Public Overrides Sub Input0_ProcessInputRow(ByVal Row As Input0Buffer)
    For Each inputColumn As IDTSInputColumn100 In Me.ComponentMetaData.InputCollection(0).InputColumnCollection
        MsgBox(inputColumn.Name)
    Next
End Sub

Building on this I try to get the values using the code below:

Public Overrides Sub Input0_ProcessInputRow(ByVal Row As Input0Buffer)
    Dim column As IDTSInputColumn100
    Dim rowType As Type = Row.GetType()
    Dim columnValue As PropertyInfo
    Dim testString As String = ""

    For Each column In Me.ComponentMetaData.InputCollection(0).InputColumnCollection
        columnValue = rowType.GetProperty(column.Name)
        testString += columnValue.GetValue(Row, Nothing).ToString()
    Next

    MsgBox(testString)

End Sub

Unfortunately this does not work and I receive the following error:

I’m sure what I am trying to do is easily achievable though my limited knowledge of VB.net and in particular VB.net in SSIS, I’m struggling. I could define the column names individually as shown here http://timlaqua.com/2012/02/slowly-changing-dimensions-with-md5-hashes-in-ssis/ though I’d like to try out a dynamic method.

Answer 1

Your problem is trying to run ToString() on a NULL value from your database.

Try Convert.ToString(columnValue) instead, it just returns an empty string.