在C＃中测试值是否为数值的正确方法

Question

I just need to know if the value is numeric. I don't need to do anything with the value. Is this the best way? Feel dirty creating a variable that I won't ever use beyond this:

int val;
if(int.TryParse(txtFoo.Text, out val))
{
    ....
}

Answer 1

Yes, using the relevant TryParse method and ignoring the out parameter is the best way of doing this.

You may want to wrap this up into your own set of helper methods (which could specify the appropriate culture etc, if the default isn't right for you) and just return a bool without the out parameter to make them easier to call.

Of course, you need to work out what kind of parsing is most appropriate - even for integers, you need to consider whether the range of Int32 is enough for your use case. In my experience, most numeric input has its own "natural" range of valid values, which is unlikely to be exactly the range of any predefined type. You may therefore want to expand your helper methods to include the range of valid values to accept.

Answer 2

It's not as flexible as int.TryParse , but you could check to see if each character is a number:

bool isInt = txtFoo.Text.All(c => char.IsNumber(c));

In general, though, I would recommend sticking with int.TryParse . You can even call the unused parameter "ignored" to be explicit about your intent, eg:

int ignored;
bool isInt = int.TryParse(txtFoo.Text, out ignored);

Answer 3

That's the best way of doing it in my knowledge - that's what our company standards adhere to anyway due to the error handling being done within the parsing.

This details the advantages: http://www.dotnetperls.com/int-tryparse

Answer 4

That is the recommended way of doing it in C#. However, you could also add Microsoft.VisualBasic.dll as a reference to your project and then use Microsoft.VisualBasic.Information.IsNumeric()

Answer 5

You can use Regular expressions

Regex _isNumber = new Regex(@"^\d+$");
_isNumber.IsMatch(txtFoo.Text);

This will only match Ints, but you can write one that also matches decimals.

Answer 6

"is numeric" is an ambiguous term.

• Culture-aware?
• Allow thousands and/or decimal separators?
• Allow scientific notation?
• Allow a sign (before? after?...)
• What range of values do you allow? Signed 32-bit integer (Int32.TryParse), Unsigned 32-bit integer (UInt32.TryParse), decimal, double, ...

Hence there is no "best" way, and the Framework provides a multitude of different ways to parse numbers.

Answer 7

bool test (string teststring) 
 { for (i=0;i==teststring.length;i++){
   if instr("0123456789.,-+Ee",teststring.substring(i,1) <0){return false;}
   // some additional tests below here if you like
   return true;
 }

however E1001E12e.12e would be noted as a number a little bit more magic is needed to do a clean check, but then you might be able to determine if its a int or a float too..

Answer 8

您可以尝试使用正则表达式解析来确定字符串中没有非数字字符，或者您可以根据输入使用Int.TryParse（），Double.TryParse（），Float.TryParse（）。