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c#typesfloating-pointreturn-value
Ali Yousefi
Ali Yousefi

Reputation: 2745

how to set value float in C#?

i want to set 20770897 to C# float type but this is changed to 20770896 ! why?

for example:

float test = 20770897;

value automatic changed to 20770896 ? help please. i am getting id from web service . these is return a float value but it is not true value from web service method!

Upvotes: 1

Views: 2345

Answers (3)

whoisj
whoisj

Reputation: 388

It's a rounding error, these are common in very large or very small values with 32-bit floating types. Use a more precise type like double if you need floating point support. If you to not explicitly need floating point support I recommend using an int, long, uint, or ulong to store the value (which appears to be an integer value).

http://en.wikipedia.org/wiki/Round-off_error

Upvotes: 2

David
David

Reputation: 10708

The issue is one of a rounding error - because of the precise way values are stored under the hood, noninteger types are incapable of string certain values, and will instead be slightly above or below the actual value. This can result in apparent errors when rounding versus truncating, and you should carefully determine which to use - presumably, you code is producing 20770896.99999... and truncating to 20770896 when you print it.

Note that errors become more frequent the higher your value gets. If you need more accuracy, consider turning up to double or even decimal types.

Upvotes: 2

Rowland Shaw
Rowland Shaw

Reputation: 38130

The precision of a float (System.Single) is only 7 significant digits

Upvotes: 8

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