TypeConverter .ConvertFromString with CultureInfo culture fails to convert decimals with grouping (thousands) char #12154
Description
Type of issue
Code doesn't work
Description
While converting german decimals from a textfile to decimals of floats, this function of the TypeConverter (TC) seems to take offense in the grouping char of the given culture (here de-DE) and results in a runtime error.
Note that when parsing text that contains a decimal, but no thousands separator, the conversions all succeed.
Code tested in LinqPad 5.5 and VS2029 with .NET 4.6.1
(sorry for the german text ;):
10.123,45 ist kein gültiger Wert für Double.
Here is the sample code from LinqPad (hence the Dump()-calls) to produce this error:
`var s = "10.123,45";
var t = typeof(double);
var tc = System.ComponentModel.TypeDescriptor.GetConverter(t);
var cult = System.Threading.Thread.CurrentThread.CurrentCulture;
decimal dec = decimal.Parse( s); //ok
dec.Dump();
var d = Convert.ChangeType(s, t, cult); //ok
dec.Dump();
var dc = tc.ConvertFromString(null, cult, s); //fails
dc.Dump();
var ds = tc.ConvertFromString(s);//fails
ds.Dump();`
After a long conversation with AIs it turns out that only using:
var d = Convert.ChangeType(s, t, cult); //ok
produces a working conversion. The explicit Parse call is out of the question as the type being used can change at runtime.
As my code does a call to TypeConverter.CanConvertFrom(targetType), I was expecting to also use the TypeConverter to actually convert the text into the desired type.
The explanation for this strange behavior by the AI was:
`
Because a TypeConverter is not primarily a “data parsing” API; it is a component-model / design-time conversion API, and the built-in numeric converters are intentionally conservative about what they accept as “canonical” text.
Concretely, DecimalConverter (and friends) parse using a restricted NumberStyles that does not include AllowThousands. That means:
It will accept forms like 123 or 123,45 (with the supplied culture), but it will reject grouped forms like 123.456,78, even though they are valid in de-DE.
The culture you pass only tells it which decimal separator and sign symbols to use; it does not change the converter’s choice of what syntactic forms are permitted. That choice is hard-coded in the converter implementation.
`
I think this should be noted in the documentation and a Link added to ChangeType
And maybe if somebody can reproduce this problem, they can raise this to get a fix?? I'm new here and have no idea how to raise bugs (which I think it is) here.
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Page URL
Content source URL
https://github.com/dotnet/dotnet-api-docs/blob/main/xml/System.ComponentModel/TypeConverter.xml
Document Version Independent Id
c197d116-9388-6449-5406-7a367dc1523d
Platform Id
e824dce0-8a22-a1e8-85f8-b059c9eb30df