Casting string in SSIS script task for for loop in C#

Question

I've just spent well over an hour finding a solution to a problem - now I'm curious as to why it works. I was getting this error in SSIS when I executed a package:

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I had a script task which was accessing a variable. I'd correctly added this to the ReadOnlyVariables collection for the script task, and was confident I'd used the right case. Here was my script line which wasn't working:

string textToWrite = (string)Dts.Variables["User::TestNumber"].Value;

Eventually I changed this to:

string textToWrite = Dts.Variables["User::TestNumber"].Value.ToString();

and everything worked OK. My question is: why did this fail before?

What is the result of running GetType() on that value? As in: string typeOfTextToWrite = Dts.Variables["User::TestNumber"].Value.GetType().ToString(). ... and what was the type of the variable in SSIS? — Brian O''Byrne
– Brian O''Byrne, Commented Apr 18, 2013 at 12:41
Variable type was Int32 in SSIS, and the line you suggest gives System.Int32. — Andy Brown
– Andy Brown, Commented Apr 18, 2013 at 18:49

saj · Accepted Answer · 2013-04-18 12:55:44Z

1

If test number is an Integer then an exception would be thrown with the first line of code because there is no type conversion defined from Int32 to string and that's why we have ToString()

answered Apr 18, 2013 at 12:55

saj

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5 Comments

Andy Brown Over a year ago

But surely (string) casts it to a string data type?

saj Over a year ago

because the explicit cast is not implemented, but a conversion is, hence why we use .ToString()

saj Over a year ago

It's a separate argument whether the cast should be implemented, but unfortunately it's not, so for now, we do .ToString()

saj Over a year ago

that's a good question and I think this thread covers it well; channel9.msdn.com/Forums/TechOff/…

Andy Brown Over a year ago

That's a great discussion. However, I think there might be something else going on here to do with SSIS. There seems to be a bug: sometimes when I execute my package it works perfectly, and on other occasions it crashes as above. Twice I've set a breakpoint in debug and this has solved the problem - even after I then remove the breakpoint. Hopefully this discussion will help someone, and thanks for your help saj.

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