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.

Code: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