DateTimeParseExact

DateTimeParseExact refers to the concept of parsing a string into a DateTime object by requiring the input to exactly match a specified format. In the .NET framework, this exact-match parsing is implemented by the methods DateTime.ParseExact and DateTime.TryParseExact, which enforce that every element of the input conforms to the given format string and culture settings.

Key features include the use of a format string, an optional culture provider, and optional parsing styles. The format string can contain standard or custom date and time specifiers, such as "yyyy-MM-dd" or "dd/MM/yyyy HH:mm:ss". When using ParseExact, a FormatException is thrown if the string does not match the format. TryParseExact, by contrast, returns a boolean indicating success or failure and places the result in an out parameter.

Overloads allow flexibility, including parsing with a single format, an array of acceptable formats, and varying DateTimeStyles to control behavior with regard to whitespace, time zones, and assumed values. For example, one can parse with an invariant culture when the input uses a fixed, culture-independent representation, or include DateTimeStyles.AdjustToUniversal for times in UTC.

Common usage scenarios include reading strictly formatted timestamps from logs, exchanging date information across systems, or validating user input that must adhere to a precise pattern. Pitfalls include mismatched formats, leading or trailing whitespace when not allowed, and cultural ambiguities that affect month and day order.

In summary, DateTimeParseExact and its closely related methods provide strict, format-driven parsing of date and time values, ensuring predictable interpretation of input strings. See also DateTime.ParseExact, DateTime.TryParseExact, and DateTimeStyles.