Depending on what type of Database you are using you will need to convert the DateTime in C# to a string.
Typically Date values are surrounded by #'s as below;
#1/1/2000#
The easiest way is to therefore convert the date to a string using
DateTime.ToString("d/M/yyyy");
Take a look at the following MSDN articles;
MSDN - DateTime.ToString(string)[
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MSDN - Standard Date and TIme Format Strings[
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MSDN - Custom Date and Time Format Strings[
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