decimal.TryParse() drops leading "1"

Question

Short and sweet version:

On one machine out of around a hundred test machines decimal.TryParse() is converting "1.01" to 0.01

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Okay, this is going to sound crazy but bear with me...

We have a client applications that communicates with a webservice through JSON, and that service returns a decimal value as a string so we store it as a string in our model object:

[DataMember(Name = "value")]
public string Value { get; set; }

When we display that value on screen it is formatted to a specific number of decimal places. So the process we use is string -> decimal then decimal -> string.

The application is currently undergoing final testing and is running on more than 100 machines, where this all works fine. However on one machine if the decimal value has a leading '1' then it is replaced by a zero. I added simple logging to the code so it looks like this:

Log("Original string value: {0}", value);
decimal val;
if (decimal.TryParse(value, out val))
{
    Log("Parsed decimal value: {0}", val);
    string output = val.ToString(format, CultureInfo.InvariantCulture.NumberFormat);
    Log("Formatted string value: {0}", output);
    return output;
}

On my machine - any every other client machine - the logfile output is:

• Original string value: 1.010000
• Parsed decimal value: 1.010000
• Formatted string value: 1.01

On the defective machine the output is:

• Original string value: 1.010000
• Parsed decimal value: 0.010000
• Formatted string value: 0.01

So it would appear that the decimal.TryParse method is at fault.

Things we've tried:

• Uninstalling and reinstalling the client application
• Uninstalling and reinstalling .net 3.5 sp1
• Comparing the defective machine's regional settings for numbers (using English (United Kingdom)) to those of a working machine - no differences.

Has anyone seen anything like this or has any suggestions? I'm quickly running out of ideas...

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While I was typing this some more info came in: Passing a string value of "10000" to Convert.ToInt32() returns 0, so that also seems to drop the leading 1.

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Further tests based on comments:

• 1.01 -> 0.01
• 111.01 -> 11.01
• 123.01 -> 23.01
• 231.01 -> 231.01
• 01.01 -> 1.01

So it would appear that it only affects 1s and only if they are the first character of the string. Very odd, but at least it's consistent.

Answer 1

I am able to reproduce your results. Consider:

public NumberFormatInfo OneIsPositiveSignFormat()
{
    NumberFormatInfo custom = new NumberFormatInfo();
    custom.PositiveSign = "1";
    return custom;
}

And then:

if (decimal.TryParse(value, NumberStyles.Number, OneIsPositiveSignFormat(), out val))

The thing is: Regional Settings does not show you the current positive sign, and mainly: you did not set the culture when parsing the number.

The value may come from various locations: It may have come from the registry as the system defaults, or the defaults could have been set by code:

CultureInfo customCulture = (CultureInfo)CultureInfo.InvariantCulture.Clone();
customCulture.NumberFormat = OneIsPositiveSignFormat();
Thread.CurrentThread.CurrentCulture = customCulture;