Best way to parse float?

Question

What is the best way to parse a float in CSharp? I know about TryParse, but what I\'m particularly wondering about is dots, commas etc.

I\'m having problems with my

Answer 1

The source is an input from a website. I can't rely on it being valid. So I went with TryParse as mentioned before. But I can't figure out how to give the currentCulture to it.

Also, this would give me the culture of the server it's currently running on, but since it's the world wide web, the user can be from anywhere...

Answer 2

Pass in a CultureInfo or NumberFormatInfo that represents the culture you want to parse the float as; this controls what characters are used for decimals, group separators, etc.

For example to ensure that the '.' character was treated as the decimal indicator you could pass in CultureInfo.InvariantCulture (this one is typically very useful in server applications where you tend to want things to be the same irrespective of the environment's culture).

Answer 3

You could always use the overload of Parse which includes the culture to use?

For instance:

double number = Double.Parse("42,22", new CultureInfo("nl-NL").NumberFormat); // dutch number formatting

If you have control over all your data, you should use "CultureInfo.InvariantCulture" in all of your code.

Answer 4

Since you don't know the web user's culture, you can do some guesswork. TryParse with a culture that uses , for separators and . for decimal, AND TryParse with a culture that uses . for separators and , for decimal. If they both succeed but yield different answers then you'll have to ask the user which they intended. Otherwise you can proceed normally, given your two equal results or one usable result or no usable result.

Answer 5

I agree with leppie's reply; to put that in terms of code:

string s = "123,456.789";
float f = float.Parse(s, CultureInfo.InvariantCulture);

Answer 6

Depends where the input is coming from.

If your input comes from the user, you should use the CultureInfo the user/page is using (Thread.CurrentThread.CurrentUICulture).

You can get and indication of the culture of the user, by looking at the HttpRequest.UserLanguages property. (Not correct 100%, but I've found it a very good first guess) With that information, you can set the Thread.CurrentThread.CurrentUICulture at the start of the page.

If your input comes from an internal source, you can use the InvariantCulture to parse the string.

The Parse method is somewhat easier to use, if your input is from a controlled source. That is, you have already validated the string. Parse throws a (slow) exception if its fails.

If the input is uncontrolled, (from the user, or other Internet source) the TryParse looks better to me.