Convert unknown string contents to numeric value

[Mark Chimes]

Hi All,

I need to search thru some strings and discard them if they canot be
converted to a decimal or interger value. What is the best way to do this?

cheers,
Mark Chimes

 

[Guest]

look at Double.TryParse

 

[Morten Wennevik [C# MVP]]

Hi Mark,

You have three ways of doing this. Since all integers are also valid
decimal numbers use

Decimal.Parse(string) // throws an exception if it is not a valid decimal
Convert.ToDecimal(string) // throws an exception if it is not a valid
decimal

Decimal d;
Decimal.TryParse(string, out d) // returns false if it is not a valid
decimal, d will contain the number

Anyhow, instead of using Decimal, you may be thinking of a Double, if so,
substitute Decimal with Double in the above code.

 

[Mark Chimes]

Hi Guys,

Thanks for the replies.
For the sake of others who may need this information and browse thru this
newsgroup, here is the "answer" I used to resolve this issue.

Iused the following code, using regular expressions, to check if the string
contained non-numeric characters. If so, the string is rejected.

using System.Text.regularExpressions;
....
bool boolIsAlpha = Regex.IsMatch(strData, @"^\p{L}*$");


cheers,
Mark Chimes

 

[Jon Skeet [C# MVP]]

Thanks for the replies.
For the sake of others who may need this information and browse thru this
newsgroup, here is the "answer" I used to resolve this issue.

Iused the following code, using regular expressions, to check if the string
contained non-numeric characters. If so, the string is rejected.

using System.Text.regularExpressions;
...
bool boolIsAlpha = Regex.IsMatch(strData, @"^\p{L}*$");

IMO, that's not a good solution:

1) It just doesn't work. It assumes that you can have anything other
than letters, and that you don't need any numbers. Here are some
strings which shouldn't be accepted but are:
""
"1+1"
"-1-1"
"1.0.0"
"1$2"

2) Using regular expressions here rather than normal code is harder to
read, IMO
3) Using regular expressions here is slower than a hard-coded
"pre-check" followed by
a simple call to TryParse. (Calling TryParse may well be fast enough;
regular expressions will be a lot slower)
4) It does no bounds checking - so even though the digits 1-10 a
thousand times each *is* a number, it's out of range of any .NET type.

Jon

 

[Mark Chimes]

Jon,

Hmmm. The data I need to parse will never hold any of the sort of values you
list, but I see what you mean.

Here's my problem.
I have large amounts of data coming to my form in an unknown state. ie: I
have no idea whether it is numerical, alpha-numerical or all alpha. For
example, I may receive "5.00%" (discard), "Total:" (discard), 2748.512
(use).

I am interested ONLY in pure numerical data, including decimal values.
I need to use only approx 5% of the data that comes to the form.

Any suggestions?

cheers,
Mark

 

[Jon Skeet [C# MVP]]

Hmmm. The data I need to parse will never hold any of the sort of values you
list, but I see what you mean.

Here's my problem.
I have large amounts of data coming to my form in an unknown state. ie: I
have no idea whether it is numerical, alpha-numerical or all alpha. For
example, I may receive "5.00%" (discard), "Total:" (discard), 2748.512
(use).

I am interested ONLY in pure numerical data, including decimal values.
I need to use only approx 5% of the data that comes to the form.

Any suggestions?

Yes - use Decimal.TryParse, or Morten suggested.