C#•8mo ago

✅ try catch

hey for example (i know tryparse exists)

var str1 = "123"
var str2 = "0ab"
var str3 = "65_"

var int1 = Convert.ToInt32(str1)
var int2 = Convert.ToInt32(str2)
var int3 = Convert.ToInt32(str3)

var str1 = "123"
var str2 = "0ab"
var str3 = "65_"

var int1 = Convert.ToInt32(str1)
var int2 = Convert.ToInt32(str2)
var int3 = Convert.ToInt32(str3)

is there a way to seperate the try / catch in a way that if int1 is valid (but int2 and int3 not) that int1 is still set

4 Replies

MODiX•8mo 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");
}

Buddy•8mo ago

Do you mean wrapping each of them in a try / catch? Not exactly sure what you mean.

Livid•8mo ago

yes, like wrapping each line in try catch

Jimmacle•8mo ago

declare the ints outside of the try/catch and then inside the try block parse them in the order you want them to be set? try/catch blocks aren't like transactions, any code that executes before an exception is thrown still modifies the program's state if you want them entirely separate then you'd have to do individual try/catch blocks but the real answer is to use TryParse

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✅ try catch