Calculating a problem and printing in a text box (C# / windows forms)

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I have started to write some basic code, I basically want to calculate 3 variables and store them in another variable called "potentialEnergy". That will then convert to a string and display in a text box called txtAns. Below is what I have but I'm very new to this..

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Incline_Impact
{


    public partial class Incline : Form
    {

        double m; //mass in kg  
        double h; //height in meters
        double g; //gravity 9.81
        double u; //coefficient of friction, 0.18 steel-steel
        double angle; //9.92 angle for our machine
        double sl; //sensor length
        double potentialEnergy;



        public Incline()
        {
            InitializeComponent();
        }

        public double Calculate(double potentialEnergy) //work on this - how to return a value
        {
            potentialEnergy = m * g * h;
            return potentialEnergy;
        }

        public void btnCalculate_Click(object sender, EventArgs e)
        {
            double defaultDouble = 0;
            
            bool m = double.TryParse(txtMass.Text, out defaultDouble);//mass in kg
            bool h = double.TryParse(txtHeight.Text, out defaultDouble);//height in meters
            bool g = double.TryParse(txtGravity.Text, out defaultDouble);//gravity 9.81 default
       

            Calculate();
            string answer = Convert.ToString(potentialEnergy);
            txtAns.Text = answer;
        }
    }
}

What I have tried:

Moving the below code inside the method Calculate:

string answer = Convert.ToString(potentialEnergy);
txtAns.Text = answer;

Posted 26-Jul-21 23:27pm

Paul Carson 2021

Updated 27-Jul-21 0:46am

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2 solutions

Solution 2

Just to add to what Richard has said ...
When you use TryParse (or TryParseExact) methods - and you definitely should - you need to check the result, and show an error if it fails instead of just blindly continueing.

Something like this:

C#

double mass= 0;
if (!double.TryParse(txtMass.Text, out mass))
    {
    MessageBox.Show("The mass needs to a a number of Kg", "Input error", MessageBoxButtons.OK);
    txtMass.Focus();
    return;
    }

Posted 27-Jul-21 0:46am

OriginalGriff

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Richard MacCutchan · Accepted Answer · 2021-07-26T23:59:00

You have defined your Calculate as taking an input parameter of a double value, and returning another double value. But when you call it in the btnCalculate_Click method, you do not pass it any value, or capture its return. also, you are trying to convert three different text strings to double values, but you store each one in the same variable, thus losing the first two. You also ignore any errors which may occur if the text dstrings are not valid numbers. You need to rework your code and think exactly what each step is required to accomplish. For example, in the btnCalculate_Click method, you need to validate each input, and take some action if it is not a valid number, or outside some minimum and maximum range. You also need to store it in the correct variable read for the calculation. And your calculate method would be better defined thus:

C#

public double Calculate(double mass, double height, double gravity)
{
    double potentialEnergy = mass * gravity * height;

    return potentialEnergy;
}

And unless you are calculating for different planets (or you are a real geek), the gravity value should be a constant.