FUNCTION: Length Conversion, is there an easier way?

This works perfectly fine but was incredibly long to write. Just wondering if there is a better way to write this. I need to be able to convert between mm, cm, in, ft, yrd, and meter and anyway in-between. I'm mainly just using this to convert numbers in the background not really part on the interface portion of the form. If anyone has any suggestions please let me know. Thanks

Code:

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    Private Sub nudCONxEnterNum_ValueChanged(sender As Object, e As EventArgs) Handles nudCONxEnterNum.ValueChanged, cbCONxLenthSelection.SelectedIndexChanged

        Dim enterNum As Decimal

        Dim MMtoCM As Decimal
        Dim MMtoIN As Decimal
        Dim MMtoFT As Decimal
        Dim MMtoYRD As Decimal
        Dim MMtoM As Decimal

        Dim CMtoMM As Decimal
        Dim CMtoIN As Decimal
        Dim CMtoFT As Decimal
        Dim CMtoYRD As Decimal
        Dim CMtoM As Decimal

        Dim INtoMM As Decimal
        Dim INtoCM As Decimal
        Dim INtoFT As Decimal
        Dim INtoYRD As Decimal
        Dim INtoM As Decimal

        Dim FTtoMM As Decimal
        Dim FTtoCM As Decimal
        Dim FTtoIN As Decimal
        Dim FTtoYRD As Decimal
        Dim FTtoM As Decimal

        Dim YRDtoMM As Decimal
        Dim YRDtoCM As Decimal
        Dim YRDtoIN As Decimal
        Dim YRDtoFT As Decimal
        Dim YRDtoM As Decimal

        Dim MtoMM As Decimal
        Dim MtoCM As Decimal
        Dim MtoIN As Decimal
        Dim MtoFT As Decimal
        Dim MtoYRD As Decimal

        Decimal.TryParse(nudCONxEnterNum.Text, enterNum)

        If cbCONxLenthSelection.SelectedIndex = 0 Then
            MMtoCM = CDec(millimeters_TO_centimeters(enterNum))
            MMtoIN = CDec(millimeters_TO_inches(enterNum))
            MMtoFT = CDec(millimeters_TO_feet(enterNum))
            MMtoYRD = CDec(millimeters_TO_yards(enterNum))
            MMtoM = CDec(millimeters_TO_meters(enterNum))
            tbCONxMM.Text = nudCONxEnterNum.Value.ToString("N4") & " mm"
            tbCONxCM.Text = MMtoCM.ToString("N4") & " cm"
            tbCONxIN.Text = MMtoIN.ToString("N4") & " in"
            tbCONxFT.Text = MMtoFT.ToString("N4") & " ft"
            tbCONxYRD.Text = MMtoYRD.ToString("N4") & " Yrd"
            tbCONxM.Text = MMtoM.ToString("N4") & " M"
        ElseIf cbCONxLenthSelection.SelectedIndex = 1 Then
            CMtoMM = CDec(centimeters_TO_millimeters(enterNum))
            CMtoIN = CDec(centimeters_TO_inches(enterNum))
            CMtoFT = CDec(centimeters_TO_feet(enterNum))
            CMtoYRD = CDec(centimeters_TO_yards(enterNum))
            CMtoM = CDec(centimeters_TO_meters(enterNum))
            tbCONxMM.Text = CMtoMM.ToString("N4") & " mm"
            tbCONxCM.Text = nudCONxEnterNum.Value.ToString("N4") & " cm"
            tbCONxIN.Text = CMtoIN.ToString("N4") & " in"
            tbCONxFT.Text = CMtoFT.ToString("N4") & " ft"
            tbCONxYRD.Text = CMtoYRD.ToString("N4") & " Yrd"
            tbCONxM.Text = CMtoM.ToString("N4") & " M"
        ElseIf cbCONxLenthSelection.SelectedIndex = 2 Then
            INtoMM = CDec(inches_TO_millimeters(enterNum))
            INtoCM = CDec(inches_TO_centimeters(enterNum))
            INtoFT = CDec(inches_TO_feet(enterNum))
            INtoYRD = CDec(inches_TO_yards(enterNum))
            INtoM = CDec(inches_TO_meters(enterNum))
            tbCONxMM.Text = INtoMM.ToString("N4") & " mm"
            tbCONxCM.Text = INtoCM.ToString("N4") & " cm"
            tbCONxIN.Text = nudCONxEnterNum.Value.ToString("N4") & " in"
            tbCONxFT.Text = INtoFT.ToString("N4") & " ft"
            tbCONxYRD.Text = INtoYRD.ToString("N4") & " Yrd"
            tbCONxM.Text = INtoM.ToString("N4") & " M"
        ElseIf cbCONxLenthSelection.SelectedIndex = 3 Then
            FTtoMM = CDec(feet_TO_millimeters(enterNum))
            FTtoCM = CDec(feet_TO_centimeters(enterNum))
            FTtoIN = CDec(feet_TO_inches(enterNum))
            FTtoYRD = CDec(feet_TO_yards(enterNum))
            FTtoM = CDec(feet_TO_meters(enterNum))
            tbCONxMM.Text = FTtoMM.ToString("N4") & " mm"
            tbCONxCM.Text = FTtoCM.ToString("N4") & " cm"
            tbCONxIN.Text = FTtoIN.ToString("N4") & " in"
            tbCONxFT.Text = nudCONxEnterNum.Value.ToString("N4") & " ft"
            tbCONxYRD.Text = FTtoYRD.ToString("N4") & " Yrd"
            tbCONxM.Text = FTtoM.ToString("N4") & " M"
        ElseIf cbCONxLenthSelection.SelectedIndex = 4 Then
            YRDtoMM = CDec(yards_TO_millimeters(enterNum))
            YRDtoCM = CDec(yards_TO_centimeters(enterNum))
            YRDtoIN = CDec(yards_TO_inches(enterNum))
            YRDtoFT = CDec(yards_TO_feet(enterNum))
            YRDtoM = CDec(yards_TO_meters(enterNum))
            tbCONxMM.Text = YRDtoMM.ToString("N4") & " mm"
            tbCONxCM.Text = YRDtoCM.ToString("N4") & " cm"
            tbCONxIN.Text = YRDtoIN.ToString("N4") & " in"
            tbCONxFT.Text = YRDtoFT.ToString("N4") & " ft"
            tbCONxYRD.Text = nudCONxEnterNum.Value.ToString("N4") & " Yrd"
            tbCONxM.Text = YRDtoM.ToString("N4") & " M"
        ElseIf cbCONxLenthSelection.SelectedIndex = 5 Then
            MtoMM = CDec(meters_TO_millimeters(enterNum))
            MtoCM = CDec(meters_TO_centimeters(enterNum))
            MtoIN = CDec(meters_TO_inches(enterNum))
            MtoFT = CDec(meters_TO_feet(enterNum))
            MtoYRD = CDec(meters_TO_yards(enterNum))
            tbCONxMM.Text = MtoMM.ToString("N4") & " mm"
            tbCONxCM.Text = MtoCM.ToString("N4") & " cm"
            tbCONxIN.Text = MtoIN.ToString("N4") & " in"
            tbCONxFT.Text = MtoFT.ToString("N4") & " ft"
            tbCONxYRD.Text = MtoYRD.ToString("N4") & " Yrd"
            tbCONxM.Text = nudCONxEnterNum.Value.ToString("N4") & " M"
        End If

    End Sub
    Private Sub btnCONxReset_Click(sender As Object, e As EventArgs) Handles btnCONxReset.Click
        ''''NOTE: "Conversions" - Reset button
        nudCONxEnterNum.Text = "1.0000"
        'cbCONxLenthSelection.SelectedIndex = 0
        nudCONxEnterNum.Focus()
    End Sub
    ''''NOTE: Conversion "MILLIMETER to XX"_______________________________________
    Public Function millimeters_TO_centimeters(ByVal answer As Decimal) As String
        Dim millimeters As Decimal = nudCONxEnterNum.Value
        answer = millimeters * 0.1D
        millimeters_TO_centimeters = answer.ToString
    End Function
    Public Function millimeters_TO_inches(ByVal answer As Decimal) As String
        Dim millimeters As Decimal = nudCONxEnterNum.Value
        answer = millimeters * 0.03937007874D
        millimeters_TO_inches = answer.ToString
    End Function
    Public Function millimeters_TO_feet(ByVal answer As Decimal) As String
        Dim millimeters As Decimal = nudCONxEnterNum.Value
        answer = millimeters * 0.003280839895D
        millimeters_TO_feet = answer.ToString
    End Function
    Public Function millimeters_TO_yards(ByVal answer As Decimal) As String
        Dim millimeters As Decimal = nudCONxEnterNum.Value
        answer = millimeters * 0.0010936132983D
        millimeters_TO_yards = answer.ToString
    End Function
    Public Function millimeters_TO_meters(ByVal answer As Decimal) As String
        Dim millimeters As Decimal = nudCONxEnterNum.Value
        answer = millimeters * 0.001D
        millimeters_TO_meters = answer.ToString
    End Function

    ''''NOTE: Conversion "CENTIMETER to XX"_______________________________________
    Public Function centimeters_TO_millimeters(ByVal answer As Decimal) As String
        Dim centimeters As Decimal = nudCONxEnterNum.Value
        answer = centimeters * 10D
        centimeters_TO_millimeters = answer.ToString
    End Function
    Public Function centimeters_TO_inches(ByVal answer As Decimal) As String
        Dim centimeters As Decimal = nudCONxEnterNum.Value
        answer = centimeters * 0.3937007874D
        centimeters_TO_inches = answer.ToString
    End Function
    Public Function centimeters_TO_feet(ByVal answer As Decimal) As String
        Dim centimeters As Decimal = nudCONxEnterNum.Value
        answer = centimeters * 0.03280839895D
        centimeters_TO_feet = answer.ToString
    End Function
    Public Function centimeters_TO_yards(ByVal answer As Decimal) As String
        Dim centimeters As Decimal = nudCONxEnterNum.Value
        answer = centimeters * 0.010936132983D
        centimeters_TO_yards = answer.ToString
    End Function
    Public Function centimeters_TO_meters(ByVal answer As Decimal) As String
        Dim centimeters As Decimal = nudCONxEnterNum.Value
        answer = centimeters * 0.01D
        centimeters_TO_meters = answer.ToString
    End Function
    ''''NOTE: Conversion "INCHES to XX"_____________________________________________
    Public Function inches_TO_millimeters(ByVal answer As Decimal) As String
        Dim inches As Decimal = nudCONxEnterNum.Value
        answer = inches * 25.4D
        inches_TO_millimeters = answer.ToString
    End Function
    Public Function inches_TO_centimeters(ByVal answer As Decimal) As String
        Dim inches As Decimal = nudCONxEnterNum.Value
        answer = inches * 2.54D
        inches_TO_centimeters = answer.ToString
    End Function
    Public Function inches_TO_feet(ByVal answer As Decimal) As String
        Dim inches As Decimal = nudCONxEnterNum.Value
        answer = inches * 0.083333333333D
        inches_TO_feet = answer.ToString
    End Function
    Public Function inches_TO_yards(ByVal answer As Decimal) As String
        Dim inches As Decimal = nudCONxEnterNum.Value
        answer = inches * 0.027777777778D
        inches_TO_yards = answer.ToString
    End Function
    Public Function inches_TO_meters(ByVal answer As Decimal) As String
        Dim inches As Decimal = nudCONxEnterNum.Value
        answer = inches * 0.0254D
        inches_TO_meters = answer.ToString
    End Function
    ''''NOTE: Conversion "FEET to XX"_____________________________________________
    Public Function feet_TO_millimeters(ByVal answer As Decimal) As String
        Dim feet As Decimal = nudCONxEnterNum.Value
        answer = feet * 304.8D
        feet_TO_millimeters = answer.ToString
    End Function
    Public Function feet_TO_centimeters(ByVal answer As Decimal) As String
        Dim feet As Decimal = nudCONxEnterNum.Value
        answer = feet * 30.48D
        feet_TO_centimeters = answer.ToString
    End Function
    Public Function feet_TO_inches(ByVal answer As Decimal) As String
        Dim feet As Decimal = nudCONxEnterNum.Value
        answer = feet * 12D
        feet_TO_inches = answer.ToString
    End Function
    Public Function feet_TO_yards(ByVal answer As Decimal) As String
        Dim feet As Decimal = nudCONxEnterNum.Value
        answer = feet * 0.33333333333D
        feet_TO_yards = answer.ToString
    End Function
    Public Function feet_TO_meters(ByVal answer As Decimal) As String
        Dim feet As Decimal = nudCONxEnterNum.Value
        answer = feet * 0.3048D
        feet_TO_meters = answer.ToString
    End Function
    ''''NOTE: Conversion "YARDS to XX"_____________________________________________
    Public Function yards_TO_millimeters(ByVal answer As Decimal) As String
        Dim yards As Decimal = nudCONxEnterNum.Value
        answer = yards * 914.4D
        yards_TO_millimeters = answer.ToString
    End Function
    Public Function yards_TO_centimeters(ByVal answer As Decimal) As String
        Dim yards As Decimal = nudCONxEnterNum.Value
        answer = yards * 91.44D
        yards_TO_centimeters = answer.ToString
    End Function
    Public Function yards_TO_inches(ByVal answer As Decimal) As String
        Dim yards As Decimal = nudCONxEnterNum.Value
        answer = yards * 36D
        yards_TO_inches = answer.ToString
    End Function
    Public Function yards_TO_feet(ByVal answer As Decimal) As String
        Dim yards As Decimal = nudCONxEnterNum.Value
        answer = yards * 3D
        yards_TO_feet = answer.ToString
    End Function
    Public Function yards_TO_meters(ByVal answer As Decimal) As String
        Dim yards As Decimal = nudCONxEnterNum.Value
        answer = yards * 0.9144D
        yards_TO_meters = answer.ToString
    End Function
    ''''NOTE: Conversion "METERS to XX"_____________________________________________
    Public Function meters_TO_millimeters(ByVal answer As Decimal) As String
        Dim meters As Decimal = nudCONxEnterNum.Value
        answer = meters * 1000D
        meters_TO_millimeters = answer.ToString
    End Function
    Public Function meters_TO_centimeters(ByVal answer As Decimal) As String
        Dim meters As Decimal = nudCONxEnterNum.Value
        answer = meters * 100D
        meters_TO_centimeters = answer.ToString
    End Function
    Public Function meters_TO_inches(ByVal answer As Decimal) As String
        Dim meters As Decimal = nudCONxEnterNum.Value
        answer = meters * 39.37007874D
        meters_TO_inches = answer.ToString
    End Function
    Public Function meters_TO_feet(ByVal answer As Decimal) As String
        Dim meters As Decimal = nudCONxEnterNum.Value
        answer = meters * 3.280839895D
        meters_TO_feet = answer.ToString
    End Function
    Public Function meters_TO_yards(ByVal answer As Decimal) As String
        Dim meters As Decimal = nudCONxEnterNum.Value
        answer = meters * 1.0936132983D
        meters_TO_yards = answer.ToString
    End Function

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I would recommend that you choose a standard unit and then implement methods to convert every other unit to and from that one. Any conversion between any other two units is then a case of first converting from the source unit to the standard and then from the standard unit to the target unit.

I'd use arrays and a dictionary(of string, decimal), with a textbox, a combobox, ten labels, and a button:

Code:

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Public Class Form1

    Private conversions As New Dictionary(Of String, Decimal)
    Private toUnits() As String = {"Millimeters", "Centimeters", "Meters", "Inches", "Feet", "Yards"}
    Private suffix() As String = {" mm", " cm", " m", " in", " ft", " yd"}
    Private unitLabels() As Label
    Private valueLabels() As Label

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        conversions.Add("Millimeters to Centimeters", 0.1D)
        conversions.Add("Millimeters to Inches", 0.03937007874D)
        conversions.Add("Millimeters to Feet", 0.003280839895D)
        conversions.Add("Millimeters to Yards", 0.0010936132983D)
        conversions.Add("Millimeters to Meters", 0.001D)
        conversions.Add("Centimeters to Millimeters", 10D)
        conversions.Add("Centimeters to Inches", 0.3937007874D)
        conversions.Add("Centimeters to Feet", 0.03280839895D)
        conversions.Add("Centimeters to Yards", 0.010936132983D)
        conversions.Add("Centimeters to Meters", 0.01D)
        conversions.Add("Inches to Millimeters", 25.4D)
        conversions.Add("Inches to Centimeters", 2.54D)
        conversions.Add("Inches to Feet", 0.083333333333D)
        conversions.Add("Inches to Yards", 0.027777777778D)
        conversions.Add("Inches to Meters", 0.0254D)
        conversions.Add("Feet to Millimeters", 304.8D)
        conversions.Add("Feet to Centimeters", 30.48D)
        conversions.Add("Feet to Inches", 12D)
        conversions.Add("Feet to Yards", 0.33333333333D)
        conversions.Add("Feet to Meters", 0.3048D)
        conversions.Add("Yards to Millimeters", 914.4D)
        conversions.Add("Yards to Centimeters", 91.44D)
        conversions.Add("Yards to Inches", 36D)
        conversions.Add("Yards to Feet", 3D)
        conversions.Add("Yards to Meters", 0.9144D)
        conversions.Add("Meters to Millimeters", 1000D)
        conversions.Add("Meters to Centimeters", 100D)
        conversions.Add("Meters to Inches", 39.37007874D)
        conversions.Add("Meters to Feet", 3.280839895D)
        conversions.Add("Meters to Yards", 1.0936132983D)

        unitLabels = New Label() {Label1, Label2, Label3, Label4, Label5}
        valueLabels = New Label() {Label6, Label7, Label8, Label9, Label10}

        For x As Integer = 0 To 4
            unitLabels(x).Text = ""
            valueLabels(x).Text = ""
        Next

        ComboBox1.DataSource = toUnits
    End Sub

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim d As Decimal
        If Decimal.TryParse(TextBox1.Text, d) Then
            Dim counter As Integer = 0
            For Each u As String In toUnits
                If u = ComboBox1.Text Then Continue For
                unitLabels(counter).Text = u & ":"
                valueLabels(counter).Text = (conversions(ComboBox1.Text & " to " & u) * d).ToString("N4") & suffix(Array.IndexOf(toUnits, u))
                counter += 1
            Next
        End If
    End Sub

End Class

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Nice, both ways seem to be much easier. I'll try them both.