C#•7mo ago

✅ Methods

Hi, i need help building a method to see if a textbox contains digits or letters. The assignment is to put in the year you are born and then give back how old you are. The tricky part for me is to build a method that will catch if you put letters in your textbox and not break down. Im not allowed to use any built in methods like tryParse och try and catch. ```cs private void Button_Click(object sender, RoutedEventArgs e) { string yearBorn = TxtYearBorn.Text; bool istrueornot = TryifStringisNumber(yearBorn);
if (istrueornot == false) { MessageBox.Show("Du får bara skriva in siffror"); } else if (istrueornot == true) { int integerYearBorn = int.Parse(yearBorn); int yearBornResult = Age(integerYearBorn); MessageBox.Show($"You are {yearBornResult} years old"); } } public bool TryifStringisNumber(string yearborn) { for (int i = 0; i < yearborn.Length; i++) { if (i <= 0 ) { return false; } else {
return true; } } return false; } private int Age(int yearOfBirth) { if (yearOfBirth >= 0) { return -1; } else { int currentyear = DateTime.Now.Year; return currentyear - yearOfBirth; } }
} }

25 Replies

Angius•7mo ago

Loop over all of the characters and return false if you encounter a non-number char.IsNumber() will be useful Or check for ASCII value ranges

olleeee•7mo ago

like how? isnt char.IsNumber a built in method?

Angius•7mo ago

If you can't even use that, then ASCII ranges it is

MODiX•7mo ago

Angius

REPL Result: Success

new { zero = (int)'0', nine = (int)'9' }

new { zero = (int)'0', nine = (int)'9' }

Result: <>f__AnonymousType0#1<int, int>

{
  "zero": 48,
  "nine": 57
}

{
  "zero": 48,
  "nine": 57
}

Compile: 320.462ms | Execution: 85.448ms | React with ❌ to remove this embed.

Angius•7mo ago

Check if the char's ASCII value is between 48 and 57 Or just if it's between '0' and '9'

MODiX•7mo ago

Angius

REPL Result: Success

'6' is > '0' and < '9'

'6' is > '0' and < '9'

Result: bool

True

True

Compile: 336.701ms | Execution: 30.589ms | React with ❌ to remove this embed.

MODiX•7mo ago

Angius

REPL Result: Success

'g' is > '0' and < '9'

'g' is > '0' and < '9'

Result: bool

False

False

Compile: 326.685ms | Execution: 47.967ms | React with ❌ to remove this embed.

Angius•7mo ago

ch >= '0' && ch <= '9' if you can't use pattern matching And ecven if you can, it should ve >= and <=, not > and < My mistake there

olleeee•7mo ago

im really confused here since i have only programmed i C# for a month...

Angius•7mo ago

Every string is a collection of chars

MODiX•7mo ago

Angius

REPL Result: Success

foreach (var letter in "hello")
{
    Console.WriteLine($"Letter is: {letter}");
}

foreach (var letter in "hello")
{
    Console.WriteLine($"Letter is: {letter}");
}

Console Output

Letter is: h
Letter is: e
Letter is: l
Letter is: l
Letter is: o

Letter is: h
Letter is: e
Letter is: l
Letter is: l
Letter is: o

Compile: 579.490ms | Execution: 57.705ms | React with ❌ to remove this embed.

Angius•7mo ago

And every char has an int associated with it, according to the ASCII table

MODiX•7mo ago

Angius

REPL Result: Success

(int)'K'

(int)'K'

Result: int

Compile: 279.950ms | Execution: 21.356ms | React with ❌ to remove this embed.

Angius•7mo ago

Combining those two, every char in a string has an associated number

MODiX•7mo ago

Angius

REPL Result: Success

foreach (var letter in "hello")
{
    Console.WriteLine($"Letter {letter} has ASCII number {(int)letter}");
}

foreach (var letter in "hello")
{
    Console.WriteLine($"Letter {letter} has ASCII number {(int)letter}");
}

Console Output

Letter h has ASCII number 104
Letter e has ASCII number 101
Letter l has ASCII number 108
Letter l has ASCII number 108
Letter o has ASCII number 111

Letter h has ASCII number 104
Letter e has ASCII number 101
Letter l has ASCII number 108
Letter l has ASCII number 108
Letter o has ASCII number 111

Compile: 578.712ms | Execution: 46.851ms | React with ❌ to remove this embed.

Angius•7mo ago

Char '0' has the value of 48 Char '9' has the value of 57

olleeee•7mo ago

yes im with you so far

Angius•7mo ago

If a given char has a value that's higher or equal to 48 and lower or equal to 57, it means that char represents a number

olleeee•7mo ago

true, but how do i change the whole string to ASCCI letters?

Angius•7mo ago

The string already is a list of characters And each character already is it's ASCII value See here I just looped over the string "hello" and got both letters and their values out of it, inside the loop

olleeee•7mo ago

oh okey, i think the console write through me of because we only work in WPF and not console!

Angius•7mo ago

Oof, that means you're kinda working ass-backwards. WPF is complex and hard, it should absolutely not be how you teach C#

olleeee•7mo ago

yeah the course I'm reading is ridiculous, so many people have actually dropped out because of it! We even doing OOP when this is for many the first programming course.

Pobiega•7mo ago

That last part isn't too weird tbh, but starting with WPF is. Anyways, did ZZZ's advice get you unstuck?

olleeee•7mo ago

yes it did! just hoping the teacher excepts it! oh okey, because when i read python we didnt do OOP so was just a chock for me personally maybe

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