How to Math Operation at one textbox in VB>Net

Question

Dear All, if I input a number and plus sign in a textbox. and when I click Button1, the Result Textbox will display the sum = 25

Answer 1

This will get you started

    Dim dt As New DataTable
    Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
        Dim result As Double = CDbl(dt.Compute(textBoxFormula.Text, Nothing))
        textBoxResult.Text = result.ToString
        'Stop
    End Sub

If you want to parse the string then some reading, a lot of reading... https://www.google.com/search?client=firefox-b-1-d&q=shunting+yard+algorithm

Answer 2

Hi An alternative. Not a trivial question despite what you may think - it gets very difficult very soon. Here is a stand alone example (with NO error checking), which tries to handle a simple + or - function with 2 numbers only. It is quite messy, but then that is part of the difficulty for this type of coding (can be tidied up though) If you want to try this, start a new test project, add TextBox1, TextBox2 and Button1 to Form1 then copy/replace all Form1 default code with this code.

' Form1 with TextBox1 and TextBox2
' and Button1
Option Strict On
Option Explicit On
Public Class Form1
	Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
		Dim s As String = TextBox1.Text

		Dim p1 As Integer = part(Trim(s))

		s = s.Remove(0, p1.ToString.Length)

		Dim op As String = s(0)

		s = s.Substring(1, s.Length - 1)

		Dim p2 As Integer = part(Trim(s))

		Select Case op
			Case "+"
				TextBox2.Text = (p1 + p2).ToString
			Case "-"
				TextBox2.Text = (p1 - p2).ToString
		End Select
	End Sub
	Function part(s As String) As Integer
		Dim v As Integer = 0
		Dim x As Integer = 0
		For i As Integer = 1 To s.Length
			Dim s2 As String = s.Substring(0, i)
			Integer.TryParse(s2, v)
			If v = 0 Then Exit For
			x = v
		Next
		Return x
	End Function
End Class

Answer 3

A way is to use MS ScriptControl with VBScript. Test with TextBox1 & TextBox2 :

  Dim objScriptControl = Activator.CreateInstance(Type.GetTypeFromCLSID(Guid.Parse("0E59F1D5-1FBE-11D0-8FF2-00A0D10038BC")))
            objScriptControl.Language = "VBScript"
            Dim objResult As Object = objScriptControl.Eval(TextBox1.Text)
            TextBox2.Text = objResult.ToString()

Answer 4

Hi All,

Thank you alot for your answer very helpfull..