Parse v. TryParse

问题:

What is the difference between Parse() and TryParse()?

int number = int.Parse(textBoxNumber.Text);

// The Try-Parse Method
int.TryParse(textBoxNumber.Text, out number);

Is there some form of error-checking like a Try-Catch Block?

回答1:

Parse throws an exception if it cannot parse the value, whereas TryParse returns a bool indicating whether it succeeded.

TryParse does not just try/catch internally - the whole point of it is that it is implemented without exceptions so that it is fast. In fact the way it is most likely implemented is that internally the Parse method will call TryParse and then throw an exception if it returns false.

In a nutshell, use Parse if you are sure the value will be valid; otherwise use TryParse.

回答2:

If the string can not be converted to an integer, then

• int.Parse() will throw an exception
• int.TryParse() will return false (but not throw an exception)

回答3:

The TryParse method allows you to test whether something is parseable. If you try Parse as in the first instance with an invalid int, you\'ll get an exception while in the TryParse, it returns a boolean letting you know whether the parse succeeded or not.

As a footnote, passing in null to most TryParse methods will throw an exception.

回答4:

TryParse and the Exception Tax

Parse throws an exception if the conversion from a string to the specified datatype fails, whereas TryParse explicitly avoids throwing an exception.

回答5:

TryParse does not return the value, it returns a status code to indicate whether the parse succeeded (and doesn\'t throw an exception).

回答6:

For the record, I am testing two codes: That simply try to convert from a string to a number and if it fail then assign number to zero.

        if (!Int32.TryParse(txt,out tmpint)) {
            tmpint = 0;
        }

and:

        try {
            tmpint = Convert.ToInt32(txt);
        } catch (Exception) {
            tmpint = 0;
        }

For c#, the best option is to use tryparse because try&Catch alternative thrown the exception

A first chance exception of type \'System.FormatException\' occurred in mscorlib.dll

That it is painful slow and undesirable, however, the code does not stop unless Debug\'s exception are settled for stop with it.

回答7:

I know its a very old post but thought of sharing few more details on Parse vs TryParse.

I had a scenario where DateTime needs to be converted to String and if datevalue null or string.empty we were facing an exception. In order to overcome this, we have replaced Parse with TryParse and will get default date.

Old Code:

dTest[i].StartDate = DateTime.Parse(StartDate).ToString(\"MM/dd/yyyy\");
dTest[i].EndDate = DateTime.Parse(EndDate).ToString(\"MM/dd/yyyy\");

New Code:

DateTime startDate = default(DateTime);
DateTime endDate=default(DateTime);
DateTime.TryParse(dPolicyPaidHistories[i].StartDate, out startDate);
DateTime.TryParse(dPolicyPaidHistories[i].EndDate, out endDate);

Have to declare another variable and used as Out for TryParse.

回答8:

double.Parse(\"-\"); raises an exception, while double.TryParse(\"-\", out parsed); parses to 0 so I guess TryParse does more complex conversions.