C#•3y ago

Validation help

Need help with some simple validation

20 Replies

cgxlmOP•3y ago

I realize whats wrong Im just not certain on how I fix it if i enter a letter this line obviously cant convert it double isales = Convert.ToDouble(sales); How do i fix

Angius•3y ago

$tryparse

MODiX•3y ago

The TryParse pattern is considered best practice of parsing data from a string: - a TryParse method returns true or false to inform you if it succeeded or not, so you can use it directly in a condition, - since C# 7 you can declare a variable that will be used as an out argument inline in an argument list, - it forces you to check if the out argument contains valid data afterwards, Avoid: Convert.ToInt32 — it's a bad choice for parsing an int. It exists only for backwards compatibility reasons and should be considered last resort.

return Convert.ToInt32(null); //returns 0. null should not be considered as 0 ever
return Convert.ToInt32("asdf"); //throws FormatException

return Convert.ToInt32(null); //returns 0. null should not be considered as 0 ever
return Convert.ToInt32("asdf"); //throws FormatException

(Note: Convert does contain useful conversion methods: To/FromBase64String, To/FromHexString, ToString(X value, int toBase), ToX(string? value, int fromBase)) Avoid: int.Parse — you have to use a try/catch statement to handle invalid input, which is a less clean solution.

var number = int.Parse("abc"); //throws FormatException
var number = int.Parse(""); //throws FormatException

var number = int.Parse("abc"); //throws FormatException
var number = int.Parse(""); //throws FormatException

Use int.TryParse https://docs.microsoft.com/en-us/dotnet/api/system.int32.tryparse?view=net-5.0#System_Int32_TryParse_System_String_System_Int32__

if (int.TryParse(someInput, out var result))
{
  Console.WriteLine($"Thanks for giving me the following number: {result}!");
}
else
{
  Console.WriteLine("You didn't give me a valid number :c");
}

if (int.TryParse(someInput, out var result))
{
  Console.WriteLine($"Thanks for giving me the following number: {result}!");
}
else
{
  Console.WriteLine("You didn't give me a valid number :c");
}

Int32.TryParse Method (System)

Converts the string representation of a number to its 32-bit signed integer equivalent. A return value indicates whether the operation succeeded.

Angius•3y ago

This method was made for this explicit reason It checks if your string can be converted into a given numeric type, and if so, converts it

cgxlmOP•3y ago

im finding it a bit confusing to understand, where would i put this in my code and what would i need to change

Angius•3y ago

You'd use it instead of your convert

cgxlmOP•3y ago

Ahhh I see ive got it in now and its working thank you

cgxlmOP•3y ago

cgxlmOP•3y ago

How would I return overtime so I can use it down there @Angius

Angius•3y ago

result is your parsed number

cgxlmOP•3y ago

yeah but how do i still get it down to use there because changing overtime to result it still cant reach it

Angius•3y ago

You're trying to use the variable in the outermost scope So you need to declare it in the outermost scope And instead of out var result in your tryparse, you can then use out thatOuterVariable

cgxlmOP•3y ago

so do i put int overtimetotal = (overtime * 15); inside of the parse one

Angius•3y ago

Try and see

cgxlmOP•3y ago

Angius•3y ago

Well, that's not how you do it, then $scopes

MODiX•3y ago

scope A {
  thing a;
  scope B {
    thing b;
  }
}

scope A {
  thing a;
  scope B {
    thing b;
  }
}

thing a is available in scope A and scope B thing b is available only in scope B

cgxlmOP•3y ago

im confused so where abouts do i put it

Angius•3y ago

You're trying to use the overtimetotal variable in the outermost scope So you need to declare it in the outermost scope

int foo = 0;
{
  {
    {
      {
        foo += 10;
      }
    }
  }
}
Console.WriteLine(foo);

int foo = 0;
{
  {
    {
      {
        foo += 10;
      }
    }
  }
}
Console.WriteLine(foo);

That's the tl;dr

cgxlmOP•3y ago

ohhhhhhhh isee now thank you so much taking me a while to wrap my head around it lol

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Validation help