# How to round and truncate long decimal strings in vb.net

I will have string data coming in, with 1, 2, or 3 digits preceding the decimal point, and 12 digits after the decimal point.  An example would be 12.918171615141.  I need to truncate everything past the 4th decimal digit, so that my example string would look like 12.9181.

Better yet would be if I could ROUND it properly, so that in this example I would end up with 12.9182.  But to do so, I assume I would have to move the string to a numeric variable and use a math function.  IF this is feasible, I need some sample code to handle this as well, i.e. how to properly get it into a numeric variable, then do the rounding, and get it back in to a string.  TIA
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Billing EngineerCommented:
0
Commented:
``````Dim yv as double
yv=12.918171615141
yv=Math.Round(yv, 3, MidpointRounding.AwayFromZero)
``````
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Author Commented:
In this example from Randy Poole, what is the right way to get my string into the numeric variable?  If my string is named strABC, do I simply say "yv=strABC"...or what is best?

I really do need some sample showing me how to properly get the string into a numeric variable, then do the rounding, and get it back in to a string
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Senior .Net DeveloperCommented:
``````Dim yv as Double

if Double.TryParse(strABC, out yv) then
'strABC a valid decimal.
yv = Math.Round(yv, 3, MidpointRounding.AwayFromZero)
strABC = yv.ToString()
else
yv = nothing
'string improperly formated, couldn't parse as a number.
end if

``````
0

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