vb.net what is a good way of displaying a decimal with a given maximum length

Question

I am writing a custom totaling method for a grid view. I am totaling fairly large numbers so I'd like to use a decimal to get the total. The problem is I need to control the maximum length of the total number. To solve this problem I started using float but it doesn't seem to support large enough numbers, I get this in the totals column(1.551538E+07). So is there some formating string I can use in .ToString() to guarentee that I never get more then X characters in the total field? Keep in mind I'm totaling integers and decimals.

Answer 1

You could use Decimal.Round, but I don't understand the exact question, it sounds like you're saying that if the total adds up to 12345.67, you might only want to show 4 digits and would then show 2345 or do you just mean that you want to remove the decimals?

Answer 2

If you're fine with all numbers displaying in scientific notation, you could go with "E[numberOfDecimalPlaces]" as your format string.

For example, if you want to cap your strings at, say, 12 characters, then, accounting for the one character for the decimal point and five characters needed to display the exponential part, you could do:

Function FormatDecimal(ByVal value As Decimal) As String
    If value >= 0D Then
        Return value.ToString("E5")
    Else
        ' negative sign eats up another character '
        Return value.ToString("E4")
    End If
End Function

Here's a simple demo of this function:

Dim d(5) As Decimal

d(0) = 1.203D
d(1) = 0D
d(2) = 1231234789.432412341239873D
d(3) = 33.3218403820498320498320498234D
d(4) = -0.314453908342094D
d(5) = 000032131231285432940D

For Each value As Decimal in d
    Console.WriteLine(FormatDecimal(value))
Next

Output:

1.20300E+000
0.00000E+000
1.23123E+009
3.33218E+001
-3.1445E-001
3.21312E+016