[ssis] How do I format date value as yyyy-mm-dd using SSIS expression builder?

hi I have taking flatfile source name dynamically I.e. filename like "source 2011-08-11" I'm creating expression builder for taking most recent file as per filename. I did like Created one variable which is having folder path : C\backup\

now inside expression builder how can i add date ??? i tried like

@[User::DirPath]+"source"+ (DT_STR,4,1252)YEAR( DATEADD( "dd", -1, getdate() ))
+"-"+(DT_STR,4,1252)MONTH( DATEADD( "dd",-1, getdate() ))+"-"+(DT_STR,4,1252) 
DAY(DATEADD( "dd", -1, getdate() )) +".CSV"

which is wrong please give me the expression which gives me output : "source 2011-08-11"

Looks like you created a separate question. I was answering your other question How to change flat file source using foreach loop container in an SSIS package? with the same answer. Anyway, here it is again.

Create two string data type variables namely DirPath and FilePath. Set the value C:\backup\ to the variable DirPath. Do not set any value to the variable FilePath.

Select the variable FilePath and select F4 to view the properties. Set the EvaluateAsExpression property to True and set the Expression property as @[User::DirPath] + "Source" + (DT_STR, 4, 1252) DATEPART("yy" , GETDATE()) + "-" + RIGHT("0" + (DT_STR, 2, 1252) DATEPART("mm" , GETDATE()), 2) + "-" + RIGHT("0" + (DT_STR, 2, 1252) DATEPART("dd" , GETDATE()), 2)