Formatting a String to be Converted to Double

I'm trying to convert a string to double. The incoming string is always going to be a whole number...no decimals. So, for example "90".

double percentToCheck = Convert.ToDouble(String.Format("{0:0.00}", SomeEntity.KeyIDs.SomePercentTrigger));

SomePercentTrigger is the % that I will be converting.

I get a "string is not in the correct format" error so how 开发者_开发百科should I format this string? I've got to format it because if I don't I get the same error with just this during the conversion:

double percentToCheck = Convert.ToDouble(SomeEntity.KeyIDs.SomePercentTrigger);

UPDATED:

SomePercentTrigger is simply a string such as "80"..it'll always be a whole number too.

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Update:
Your string is "52.0".

It must be the '.' that causes the FormatException.
You are probably on a machine where '.' is not set as the decimal point (e.g. I live in Germany and use German regional settings. Our decimal point is ',' )

To get around this problem you need to parse the string using CultureInfo.InvariantCulture.

var value = double.Parse(myString, CultureInfo.InvariantCulture);

InvariantCulture should be used for the parts of your application that revolve around data storage. Make sure you use it as well when converting doubles to strings Console.WriteLine(value.ToString(CultureInfo.InvariantCulture));

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I suspect that SomeEntity.KeyIDs.SomePercentTrigger has some invalid characters in it (something other than digits, '.' and a optional leading '-'), say for example "80%"

So you're getting a FormatException on this line

double percentToCheck = Convert.ToDouble(String.Format("{0:0.00}", SomeEntity.KeyIDs.SomePercentTrigger));

because {0:0.00} formatting rules are only valid for numeric values.

Also you get the very same exception here:

double percentToCheck = Convert.ToDouble(SomeEntity.KeyIDs.SomePercentTrigger);

because "80%" can not be converted into a double.

You should either

• put some logging right in front of the failing statement
• or debug that code

and see what the actual content of SomeEntity.KeyIDs.SomePercentTrigger is.

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Use double.Parse(string) or alternatively double.TryParse(string, out value)

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It doesn't make sense to try to format a string. You would have to parse it to a number first in order to format it. Anyhow, there is no problem in parsing a number without decimals as a double, so the string is probably not containing what you think it does.

If the string contains a number in integer format, parse the string as an integer, and then convert the integer to a double:

double percentToCheck = (double)Int32.Parse(SomeEntity.KeyIDs.SomePercentTrigger);