Populate Derived Column with File's Date Modified - ssis

Question

I'm a wannabe to .Net and SQL and am working on an SSIS package that is pulling data from flat files and inputting it into a SQL table. The part that I need assistance on is getting the Date Modified of the files and populating a derived column I created in that table with it. I have created the following variables: FileDate of type DateTime, FilePath of String, and SourceFolder of String for the path of the files. I was thinking that the DateModified could be populated in the derived column w/i the DataFlow, using a Script Component? Can someone please advise on if I'm on the right track? I appreciate any help. Thanks.

Answer 1

A Derived Column Transformation can only work with Integration Services Expressions. A script task would allow you to access the .net libraries and you would want to use the method that #wil kindly posted or go with the static methods in System.IO.File
However, I don't believe you would want to do this in a Data Flow Task. SSIS would have to evaluate that code for every row that flows through from the file. On a semi-related note, you cannot write to a variable until the ... event is fired to signal the data flow has completed (I think it's OnPostExecute but don't quote me) so you wouldn't be able to use said variable in a downstream derived column at any rate. You would of course, just modify the data pipeline to inject the file modified date at that point.
What would be preferable and perhaps your intent is to use a Script Task prior to the Data Flow task to assign the value to your FileDate variable. Inside your Data Flow, then use a Derived Column to add the #FileDate variable into the pipeline.
// This code is approximate. It should work but it's only been parsed by my brain
//
// Assumption:
// SourceFolder looks like a path x:\foo\bar
// FilePath looks like a file name blee.txt
// SourceFolder [\] FilePath is a file that the account running the package can access
//
// Assign the last mod date to FileDate variable based on file system datetime
// Original code, minor flaws
// Dts.Variables["FileDate"].Value = File.GetLastWriteTime(System.IO.Path.Combine(Dts.Variables["SourceFolder"].Value,Dts.Variables["FilePath"].Value));
Dts.Variables["FileDate"].Value = System.IO.File.GetLastWriteTime(System.IO.Path.Combine(Dts.Variables["SourceFolder"].Value.ToString(), Dts.Variables["FilePath"].Value.ToString()));
Edit
I believe something is amiss with either your code or your variables. Do your values approximately line up with mine for FilePath and SourceFolder? Variables are case sensitive but I don't believe that to be your issue given the error you report.
This is the full script task and you can see by the screenshot below, the design-time value for FileDate is 2011-10-05 09:06 The run-time value (locals) is 2011-09-23 09:26:59 which is the last mod date for the c:\tmp\witadmin.txt file
using System;
using System.Data;
using Microsoft.SqlServer.Dts.Runtime;
using System.Windows.Forms;
namespace ST_f74347eb0ac14a048e9ba69c1b1e7513.csproj
{
[System.AddIn.AddIn("ScriptMain", Version = "1.0", Publisher = "", Description = "")]
public partial class ScriptMain : Microsoft.SqlServer.Dts.Tasks.ScriptTask.VSTARTScriptObjectModelBase
{
enum ScriptResults
{
Success = Microsoft.SqlServer.Dts.Runtime.DTSExecResult.Success,
Failure = Microsoft.SqlServer.Dts.Runtime.DTSExecResult.Failure
};
public void Main()
{
Dts.Variables["FileDate"].Value = System.IO.File.GetLastWriteTime(System.IO.Path.Combine(Dts.Variables["SourceFolder"].Value.ToString(), Dts.Variables["FilePath"].Value.ToString()));
Dts.TaskResult = (int)ScriptResults.Success;
}
}
}
C:\tmp>dir \tmp\witadmin.txt
Volume in drive C is Local Disk
Volume Serial Number is 3F21-8G22
Directory of C:\tmp
09/23/2011 09:26 AM 670,303 witadmin.txt