C# WinForms - Adding two textbox automatically

Question

I'm building this three textbox where if the two textbox are filled the sum will be displayed however, when I input 10 + 10. The result is 1010. Can anbody help me with this?

Here's my code:

public void textBoxTranspo_TextChanged(object sender, EventArgs e) 
{
    if (!string.IsNullOrEmpty(textBoxTranspo.Text) && !string.IsNullOrEmpty(textBoxDaily.Text))
        textBoxTotalAmount.Text = (Convert.ToInt32(textBoxTranspo.Text) + Convert.ToInt32(textBoxDaily.Text).ToString());
}

public void textBoxDaily_TextChanged(object sender, EventArgs e)
{   
    if (!string.IsNullOrEmpty(textBoxTranspo.Text) && !string.IsNullOrEmpty(textBoxDaily.Text))
        textBoxTotalAmount.Text = (Convert.ToInt32(textBoxTranspo.Text) + Convert.ToInt32(textBoxDaily.Text).ToString());
}

string = string + int: What's behind the scenes?

Reza Aghaei
– Reza Aghaei

2016-11-18 03:57:08 +00:00
Commented Nov 18, 2016 at 3:57 — Reza Aghaei
– Reza Aghaei, Commented Nov 18, 2016 at 3:57

sujith karivelil · Accepted Answer · 2016-11-18 03:59:16Z

2

It is the magic(polymorphism) of the + operator. it will add the values of two operands if the operands are of numeric types(int,long, double) and it will concatenate two operands if they are of type strings or even one string and second integer(as like in your case). Here in your case the .ToString() after convert creates the issues. You will get the expected result by removing that from that line.

An additional note : Convert.ToInt32 will throw FormatException if the input text is not convertible, so use have to use int.TryParse for converting text to integer. so the code will looks like this:

int intTranspo=0,intBoxDaily=0;

if(int.TryParse(textBoxTranspo.Text,out intTranspo) && int.TryParse(textBoxDaily.Text,out intBoxDaily))
   textBoxTotalAmount.Text = (intTranspo + intBoxDaily).ToString();

answered Nov 18, 2016 at 3:59

sujith karivelil

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3 Comments

Noobster Over a year ago

Hi, I understand your answer and thank you for that but like what you've said, I tried removing your said .ToString() but it said Cannot implicitly convert type 'int' to 'string' But, overall it works like a charm! Thanks

Noobster Over a year ago

But, is it really meant to I put the int intTranspo=0,intBoxDaily=0; in the two different public void? Isn't that kind of redundant or it is just the way it is?

sujith karivelil Over a year ago

Yep, you have to declare those variable before use. Since you are passing them to the TryParse method as out params.

K.Sopheak · Accepted Answer · 2016-11-18 04:25:24Z

2

Remove toString at the end of statement.

textBoxTotalAmount.Text = (Convert.ToInt32(textBoxTranspo.Text) + Convert.ToInt32(textBoxDaily.Text))

answered Nov 18, 2016 at 4:25

K.Sopheak

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Comments

user671150 · Accepted Answer · 2016-11-18 03:57:16Z

1

Maybe it should be:

textBoxTotalAmount.Text = (Convert.ToInt32(textBoxTranspo.Text) + Convert.ToInt32(textBoxDaily.Text)).ToString();

answered Nov 18, 2016 at 3:57

user671150

1 Comment

sujith karivelil Over a year ago

care to add some explanation, why this and why not OP's

Kokombads · Accepted Answer · 2016-11-18 04:47:26Z

1

to avoid confusion, first, try to convert the values of the textboxes into int, and put it in respective variables if successful, and output an invalid prompt if not.

int input1 = 0;
int input2 = 0;

try
{
    input1 = Convert.ToInt32(textBoxTranspo.Text);
    input2 = Convert.ToInt32(textBoxDaily.Text); 
    ans = input1 + input2;


    if (!string.IsNullOrEmpty(textBoxTranspo.Text) && !string.IsNullOrEmpty(textBoxDaily.Text))
    {
        textBoxTotalAmount.Text = ans.ToString();
    }

}
catch (Exception)
{
    textBoxTotalAmount.Text = "Invalid input";
}

edited Nov 18, 2016 at 4:47

answered Nov 18, 2016 at 4:04

Kokombads

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Comments

JC Borlagdan · Accepted Answer · 2016-11-18 06:36:34Z

1

Do it like this:

int ans = 0;
ans = Convert.ToInt32(textBoxTranspo.Text) + Convert.ToInt32(textBoxDaily.Text);
textBoxTotalAmount.Text = ans.ToString();

EDIT:

This is just one way of creating a clean/neat and more readable code. The way other answered like this

textBoxTotalAmount.Text = (Convert.ToInt32(textBoxTranspo.Text) + Convert.ToInt32(textBoxDaily.Text)).ToString();

is also correct but if other programmers will read the code, the 1st one I wrote is more readable and in this case more efficient.

You're getting 1010 because you misplaced the .ToString()

edited Nov 18, 2016 at 6:36

answered Nov 18, 2016 at 3:55

JC Borlagdan

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1 Comment

sujith karivelil Over a year ago

care to add some explanation, why this and why not OP's

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