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I want to calculate a arithmetic expression from a string using VB, any ideas ?

As an example : "x+2" from a textbox, I want to evaluate the expression

Mike Woodhouse
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Dimitris Sapikas
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    I think you mean you want to execute it as an *arithmetic* expression. A *regular* expression is [something completely different](http://en.wikipedia.org/wiki/Regular_expression). I am sure you knew that already – MarkJ Nov 01 '12 at 14:10
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    possible duplicate of [Doing math in vb.net like Eval in javascript](http://stackoverflow.com/questions/1452282/doing-math-in-vb-net-like-eval-in-javascript) – Boann Dec 25 '14 at 00:26

3 Answers3

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Dim equation As String = "2+6/2"
Dim result = New DataTable().Compute(equation, Nothing)
Andrew
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you can use NCalc for this. It also accepts parameters like x, y, z,...

Dim e As Expression = new Expression("2 + 3 * 5")
Msgbox(17 = e.Evaluate())
John Woo
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2

You can use mxparser library for this purpose.Give a reference to mxparser.dll in your project by clicking ADD Reference button of Microsoft Visual Studio.The mxparser library source code or latest dll file can be from www.mathparser.org.The mXparser is a Math Parser for Java, Android, C# .NET (CLS) Libraries.

Imports org.mariuszgromada.math.mxparser
Private Function evaluate(ByVal str As String) AS Double
Dim expr As Expression = New Expression(str)
DIM d1 As Double
d1=0
d1=expr.calculate()
return d1
End Function

Call to the function can be as follows.

DIM str as String
str=""
str=((45^5)/45))*(5*6)

Dim d as Double
d=0
d=evaluate(str)
MsgBox(" The result of the expression is   " + d.ToString)
antony thomas
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  • For mXparser ( http://mathparser.org/ ) there is even nice "hello world" tutorial for VB :-) http://mathparser.org/mxparser-hello-world/mxparser-hello-world-visual-basic/ – Leroy Kegan Apr 21 '17 at 20:51