Convert to date time ??????

In my database i have datetime field,
Now i have a string as "29/12/2009 12:03:11"
I use code as :
dim str as string="29/12/2009 12:03:11"
dim t as datetime=Convert.ToDateTime(str)

T variable will be inserted into database with Time Field
But always notify error : String was not recognized as a valid DateTime.


Anyone help me fix error !!

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