+ Operator c# with string

Question

I have got this code down below which should multiply two variables and add to it amount from textbox kpriplac. but when the multiplied value is 10 and kpriplac value is for example also 10 the output is 1010. But I need that output to be 20. I have also checked this

Where do I make a mistake? Thanks for your time reading this.

if (double.TryParse(comboBoxText, out comboxValue) && int.TryParse(textBox16.Text.Trim(), out textboxValue))
{
    textBox19.Text = ((comboxValue * textboxValue) + (kpriplac.Text)).ToString();
}

Where is kpriplac.Text converted to an int?

Davin Tryon
– Davin Tryon

2013-07-22 09:23:31 +00:00
Commented Jul 22, 2013 at 9:23 — Davin Tryon
– Davin Tryon, Commented Jul 22, 2013 at 9:23

Zaheer Ahmed · Accepted Answer · 2013-07-22 09:49:45Z

2

+ operator with strings operate as concatenate operator. You need to parse string to int or float.

for example:

textBox19.Text = ((comboxValue * textboxValue) + Convert.ToInt32(kpriplac.Text)).ToString();

Edit

Pleas make sure kpriplac.Text is:

Is not empty
Not contains only spaces
Not contains the character or non convertible string.

If it then handle accordingly.

Convert Class Msdn

edited Jul 22, 2013 at 9:49

answered Jul 22, 2013 at 9:22

Zaheer Ahmed

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3 Comments

Ehsan Over a year ago

-1 because this code will throw an exception if kpriplac.Text is empty. Like Input string was not in a correct format

Ehsan Over a year ago

Not obvious for as naiive as the asker. Who doesn't even knows how concatenation of string and int work?

Ehsan Over a year ago

because i still don't like the way code is written It isn't the right way to do it. :)

lc. · Accepted Answer · 2013-07-22 09:24:23Z

2

As it stands, your code is adding a number to a string which is implicitly calling ToString() on the (comboxValue * textboxValue) expression and performing string concatenation.

You need to parse the value in kpriplac.Text into a numeric type as well, in much the same manner you are doing for comboBoxText and textBox16.Text.

answered Jul 22, 2013 at 9:24

lc.

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Comments

KappaG3 · Accepted Answer · 2013-07-22 09:24:27Z

1

You need to call int.Parse on every string, and then multiply or add the parsed values together, finally converting them back to string.

Use int.Parse only if you're sure that the given string is indeed an integer. If it isn't, exceptions are thrown. If you're unsure and want to handle them manually, use int.TryParse instead.

answered Jul 22, 2013 at 9:24

KappaG3

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Comments

Ehsan · Accepted Answer · 2013-07-22 09:38:45Z

1

You face this because

 (comboxValue * textboxValue)

is an integer,whereas

 kpriplac.Text

is a string

In C# string + int = string. So lets say multiplication returns you 10. And you have got 10 in your text box as well

so what will happen is

        10 + "10"  = 1010

Change your code to

 if (double.TryParse(comboBoxText, out comboxValue) && int.TryParse(textBox16.Text.Trim(), out textboxValue))
 {
    int tempValue = 0;
    if(int.TryParse(kpriplac.Text,out tempValue))
         textBox19.Text = ((comboxValue * textboxValue) + tempValue).ToString();
 }

edited Jul 22, 2013 at 9:38

answered Jul 22, 2013 at 9:29

Ehsan

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Comments

zxc · Accepted Answer · 2013-07-22 09:23:33Z

0

Try this

Convert.ToInt32(((comboxValue * textboxValue) + (kpriplac.Text))).ToString();

answered Jul 22, 2013 at 9:23

zxc

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1 Comment

Ehsan Over a year ago

-1 because it will not return the desired result. It will still return 1010.

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