[RESOLVED] Advice needed for a message box if not enough data entered.

[SteveHeather]

Hi all,

I have created a program that solves the right-angled triangle by just needing to input two known quantities. I have adapted this code from some I found on another website, it never actually worked, so I spent two weeks figuring out how to get it to work. I have finally succeeded, what I would like to do is display a message box if the user has not entered the required two inputs and presses the 'Calculate' button (see image). I just want it to say "At least two known quantities are required".

I have some code that clears all the text boxes so you can enter new data, but I have tried countless times to find a way of coding so the message box appears.

I would appreciate it if someone could steer me in the right direction.

Many thanks,

Steve.

Imports System.String
Imports System.Math
Public Class Form1
    Dim angleA As Single = 90
    Dim angleB As Single
    Dim angleC As Single
    Dim sidea As Single
    Dim sideb As Single
    Dim sidec As Single


#Region " If value is Null "
    Public Function isItNullString(ByVal value) As Boolean
        If value = "" Then
            Return True
        Else
            Return False
        End If
    End Function
#End Region

#Region " To find one side if two sides known - Pythagoras Theorem "
    Public Sub PythagoreanTheorem()

        If sidec <> 0 And sidea <> 0 And sideb = 0 Then
            sideb = Math.Sqrt((sidec * sidec) - (sidea * sidea))
            TextBoxSideb.Text = sideb

        ElseIf sideb <> 0 And sidea <> 0 And sidec = 0 Then
            sidec = Math.Sqrt((sideb * sideb) + (sidea * sidea))
            TextBoxSidec.Text = sidec

        ElseIf sidec <> 0 And sideb <> 0 And sidea = 0 Then
            sidea = Math.Sqrt((sidec * sidec) - (sideb * sideb))
            TextBoxSidea.Text = sidea
        End If
    End Sub
#End Region

#Region " Find Angle B or Angle C "
    Public Sub angleSums()

        If angleC = 0 And angleB <> 0 Then
            angleC = 180 - angleA - angleB
            TextBoxAngleC.Text = angleC
        End If

        If angleB = 0 And angleC <> 0 Then
            angleB = 180 - angleA - angleC
            TextBoxAngleB.Text = angleB
        End If
    End Sub
#End Region

#Region " Angle B and one side known "
    Public Sub angleBasWorkingAngle()

        'Angle B and side b known, find side c
        If angleB <> 0 And sideb <> 0 Then
            sidec = sideb / Sin(degreesToRadians(angleB))
            TextBoxSidec.Text = sidec
        End If

        'Angle B and side a known, find side b
        If angleB <> 0 And sidea <> 0 Then
            sideb = sidea * Tan(degreesToRadians(angleB))
            TextBoxSideb.Text = sideb
        End If

        'Angle B and side b known, find side a
        If angleB <> 0 And sideb <> 0 Then
            sidea = sideb / Tan(degreesToRadians(angleB))
            TextBoxSidea.Text = sidea
        End If

        'Angle B and side b known, find side a
        If angleB <> 0 And sidec <> 0 Then
            sidea = sidec * Cos(degreesToRadians(angleB))
            TextBoxSidea.Text = sidea
        End If

    End Sub
#End Region

#Region " Find Angle C "
    Public Sub findangleC()

        If angleC = 0 Then
            'cos
            angleC = radiansToDegrees(Acos(sideb / sidec))
            TextBoxAngleC.Text = angleC
        End If

    End Sub
#End Region

#Region " Feed Values "

    Public Sub feedValues()

        If Not isItNullString(TextBoxSideb.Text) Then
            sideb = TextBoxSideb.Text
        Else
            sideb = 0
        End If

        If Not isItNullString(TextBoxSidea.Text) Then
            sidea = TextBoxSidea.Text
        Else
            sidea = 0
        End If

        If Not isItNullString(TextBoxSidec.Text) Then
            sidec = TextBoxSidec.Text
        Else
            sidec = 0
        End If

        If Not isItNullString(TextBoxAngleC.Text) Then
            angleC = TextBoxAngleC.Text
        Else
            angleC = 0
        End If

        If Not isItNullString(TextBoxAngleB.Text) Then
            angleB = TextBoxAngleB.Text
        Else
            angleB = 0
        End If
    End Sub
#End Region

#Region " Convert Degrees to Radians "
    Public Function degreesToRadians(ByVal degrees As Double) As Double
        Dim radians As Double
        radians = (Math.PI * degrees) / 180
        Return radians
    End Function
#End Region

#Region " Convert Radians to Degrees "
    Public Function radiansToDegrees(ByVal radians As Double) As Double
        Dim degrees As Double
        degrees = radians * (180 / Math.PI)
        Return degrees
    End Function
#End Region

#Region " Calculate all Data "
    Private Sub btnCalc_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalc.Click
        For aaa As Integer = 0 To 2 'I just repeated this 6 times because I have a lot of processing power
            'you can do it twice.

            feedValues()

            PythagoreanTheorem()

            angleSums()

            angleBasWorkingAngle()

            findangleC()

        Next
        
    End Sub
#End Region

#Region " Clear all input boxes "
    Public Sub ClearTextBox(ByVal root As Control)
        For Each ctrl As Control In root.Controls
            ClearTextBox(ctrl)
            If TypeOf ctrl Is TextBox Then
                CType(ctrl, TextBox).Text = String.Empty
            End If
        Next ctrl
    End Sub
#End Region

#Region " Button to clear all Input boxes "
    Private Sub btnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClear.Click
        ClearTextBox(Me)
    End Sub
#End Region

#Region " Button to Exit the program "
    Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExit.Click
        Me.Close()
    End Sub
#End Region

End Class