How to add an argument modifier to a method in C#?

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I made this calculator in C# and it was working fine, but, when I add a method with argument modifier out for the percentage option, the calculator stopped working and the error statement declares that "

the out parameter must be assigned to before control leaves the current method

", how is that possible? I am perfectly assigning the value before control leaves the method. Any idea why is this happening?
Thanks

namespace Calculator2
{
    public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();

            Button button = new Button
            {

                HorizontalOptions = LayoutOptions.Center,
                VerticalOptions = LayoutOptions.Center

            };

            button.Clicked += async (sender, args) =>
            {
                await Navigation.PushAsync(new MainPage());

            };

        }
        private void Button_Click(object sender, EventArgs e)
        {
          
            var key = operation.Text;
            

            int num1 = Convert.ToInt32(number1.Text);

            int num2 = int.Parse(number2.Text);
            float intpercent = 0;
            label3.Text = calculator.DoSomeMath(num1, num2, key).ToString();

            calculator.DoSomeMath(num1, num2, out intpercent, key);
                  
        }
        public class calculator
        {
          
            public static int DoSomeMath(int num1, int num2, string key)
            {
              
                string operation=key; 
                if(operation=="Add")
                {                 
                    int sum = num1 + num2;

                    return sum;
                } else if (operation == "Minus")
                {
                    int substract = (int)(num1 - num2);
                    return substract;
                } else if (operation == "Multiply")
                {
                    int Multiply = (int)(num1 * num2);

                    return Multiply;
                }
                else if (operation == "Divide")
                {
                    int Divide = (int)(num1/num2);

                    return Divide;
                }else
                return 0;
               

            }
            public static float DoSomeMath(float num1, float num2, string key)
            {

                string operation = key;
                if (operation == "Add")
                {

                    float sum = num1 + num2;

                    return sum;
                }
                else if (operation == "Minus")
                {
                    float Substract = (float)(num1 - num2);
                    return Substract;
                }
                else if (operation == "Multiply")
                {
                    float Multiply = (float)(num1 * num2);

                    return Multiply;
                }
                else if (operation == "Divide")
                {
                    float Divide = (float)(num1 / num2);

                    return Divide;
                }
                return 0;

            }
          
            public static void DoSomeMath(int num1, int num2, out float percentage, string key)
            {
                
                string operation = key;
                do
                {
                    percentage = ((float)num1 / (float)num2) * 100;
                } while (operation == "percentage");



            }

        }


    }
}

What I have tried:

-I tried by changing the argument modifier out by ref.
-I placed

percentage = ((float)num1 / (float)num2) * 100;

before the method

Posted 18-Dec-21 19:01pm

Diasalva5

Updated 18-Dec-21 20:30pm

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OriginalGriff · Accepted Answer · 2021-12-18T20:14:00

If I copy and paste your code into an online compiler:

using System;
namespace ReadXml1
{
    internal class Class1
    {
        private static void Main(string[] args)
        {
			string[] data = {"hello", "world"};
			Console.WriteLine(String.Join(" ", data));
            int num1 = 666;
			string key = "Add";
            int num2 = 3;
            float intpercent = 0;
            string Text = calculator.DoSomeMath(num1, num2, key).ToString();
			Console.WriteLine(Text);
            calculator.DoSomeMath(num1, num2, out intpercent, key);
			Console.WriteLine(intpercent);
        }
    }
        public class calculator
        {
          
            public static int DoSomeMath(int num1, int num2, string key)
            {
              
                string operation=key; 
                if(operation=="Add")
                {                 
                    int sum = num1 + num2;

                    return sum;
                } else if (operation == "Minus")
                {
                    int substract = (int)(num1 - num2);
                    return substract;
                } else if (operation == "Multiply")
                {
                    int Multiply = (int)(num1 * num2);

                    return Multiply;
                }
                else if (operation == "Divide")
                {
                    int Divide = (int)(num1/num2);

                    return Divide;
                }else
                return 0;
               

            }
            public static float DoSomeMath(float num1, float num2, string key)
            {

                string operation = key;
                if (operation == "Add")
                {

                    float sum = num1 + num2;

                    return sum;
                }
                else if (operation == "Minus")
                {
                    float Substract = (float)(num1 - num2);
                    return Substract;
                }
                else if (operation == "Multiply")
                {
                    float Multiply = (float)(num1 * num2);

                    return Multiply;
                }
                else if (operation == "Divide")
                {
                    float Divide = (float)(num1 / num2);

                    return Divide;
                }
                return 0;

            }
          
            public static void DoSomeMath(int num1, int num2, out float percentage, string key)
            {
                
                string operation = key;
                do
                {
                    percentage = ((float)num1 / (float)num2) * 100;
                } while (operation == "percentage");



            }

        }
}

It compiles and runs cleanly. I get results:

hello world
669
22200

So it's unlikely that your code as shown is generating that error: If you have had this:

public static void DoSomeMath(int num1, int num2, out float percentage, string operation)
{
    while (operation == "percentage")
    {
        percentage = ((float)num1 / (float)num2) * 100;
    }
}

Or this:

public static void DoSomeMath(int num1, int num2, out float percentage, string operation)
{
    if (operation == "percentage")
    {
        percentage = ((float)num1 / (float)num2) * 100;
    }
}

Then you would, because in both cases there is a path through the code where the value of percentage is not assigned.
But your do ... whileloop always executes a minimum of once so it is always set.

Check your code: I don't think you are compiling what you think you are!

BTW: setting the value of an out parameter before calling a method is irrelevant as teh value is not passed into the method at all!