C# cannot implicitly convert type int to string

Question

2.50/5 (2 votes)

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I have done this calculator, and I have passed the arguments to the method and the parse have been done, however, is still having a wavy red line under

calculator.DoSomeMath(num1, num2)

and when hovered over that area it displays "

Cannot implicitly convert type int to string

Any suggestions? Thanks

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

       }
       private void Button_Click(object sender, EventArgs e)
       {

           int num1 = int.Parse(number1.Text);

           int num2 = int.Parse(number2.Text);

           label3.Text = calculator.DoSomeMath(num1, num2);


       }

   }

       class calculator
       {

       public static int DoSomeMath(int num1, int num2)
       {

           int sum;
           sum = num1 + num2;
           return sum;

        }

   }

What I have tried:

I have tried
-

DoSomeMath.ToString(num1, num2);

-

label3.Text = calculator.DoSomeMath.(num1.ToString, num2.ToString);

-

label3.Text = calculator.int.Parse(DoSomeMath.(num1.ToString, num2.ToString));

-

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

int num2 = Convert.ToInt32(number2.Text);

Posted 10-Dec-21 13:49pm

Diasalva5

Updated 10-Dec-21 20:00pm

v2

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BillWoodruff · Answer 1 · 2021-12-10T18:33:00

Solution 1

C#

// convert to string:
label3.Text = calculator.DoSomeMath(num1, num2).ToString();

Use 'TryParse to make sure the input values are valid:

C#

int value1, int value2;

if(! Int32.TryParse(num1, out value1))
{ 
     Console.WriteLine($"cannot convert {num1} to number");
     return;
}

// repeat test for 'num2

Posted 10-Dec-21 18:33pm

BillWoodruff

Updated 10-Dec-21 21:58pm

v2

Comments

Diasalva5 11-Dec-21 11:34am

Dear Mr.BillWoodruff
It worked, Thanks. I had done something similar, but the one that you advised me was the one that worked.
THANK YOU!!

OriginalGriff · Answer 2 · 2021-12-10T20:00:00

To expand on what Bill has - rightly - said ...
C# is a "strongly typed" language, which means that it assumes you know what you are doing, and it doesn't - so it won't make an assumption about what you want and convert data from type to type for you, unless that conversion would result in a very similar type without any loss of information.

So it will happily "upgrade" an integer to a float or double:

C#

int x = 666;
float y = x;

C#

int x = 666;
double y = x;

because both types are numeric and there is no loss of data.But it won't convert the other way:

C#

float x = 666.0f;
int y = x;

C#

double x = 666.0;
int y = x;

because integers can't store fractional parts of a number.
To do that, you have to explicitly tell the system what you want to do using a cast operation:

C#

float x = 666.0f;
int y = (int) x;

C#

double x = 666.0;
int y = (int) x;

And the same applies when you try to do this:

C#

int x = 666;
string y = x;

will fail because the two types are too different and you can't cast between them.

To assign a numeric value to a string, you have to explicitly tell the system to do the conversion:

C#

int x = 666;
string y = x.ToString();

And the ToString method can take a parameter which tells it how to format the number when you convert it: UInt32.ToString Method (System) | Microsoft Docs[^]