Is there a way to compress a check that returns a nullable boolean this into 1-2 lines?-CodePudding

I'm making a simple C# console app and the user has to input either a 1 or a 2 to select their option, and obviously since the user can enter absolutely anything, I need to make a check that returns their input and if it isn't a 1 or a 2, it'll return null.

This is what I made

bool? getResponse = null;
if (read == "1")
{
    getResponse = true;
}
else if (read == "2")
{
    getResponse = false;
}
else
{
    getResponse = null;
}

Knowing C#, there's definitely a way to simplify this but I cant seem to find a way to online. Any pointers?

CodePudding user response：

Probably you are looking for conditional operator ?:.

But this could be complex to maintain and difficult to read if the logic is getting complex (adding logic for read == "3" and etc.).

getResponse = read == "1" 
    ? true 
    : read == "2" 
        ? true 
        : null;

Another approach you can apply is switch expression for C# 9.

getResponse = read switch
{
    "1" => true,
    "2" => false,
    _ => null,
};

The third approach is you work around with Dictionary.

using System.Collections.Generic;
using System.Linq;

Dictionary<string, bool> resultDict = new Dictionary<string, bool>
{
    { "1", true },
    { "2", false }
};
        
getResponse = resultDict.TryGetValue(read, out bool _result) 
    ? _result 
    : null;

CodePudding user response：

You can use ternary operator in a such situations like this

string read = Console.ReadLine();

bool? response = read == "1" ? true
: read == "2" ? false : null;

but it's best when there is only 2 possible ways, as u can see it's getting out of hand easily. In this situation my code above is ok, but if you have like 10 possibilities maybe something like this is a good approach

// lets say there is ways 
// 1 = true, 2 = false, 3 = null
// and any other input means exception

string read = Console.ReadLine()!;

Dictionary<string, bool?> keyValues = new();
keyValues.Add("1", true);
keyValues.Add("2", false);
keyValues.Add("3", null);

bool? response = keyValues.ContainsKey(read) ? keyValues[read] 
    : throw new Exception();

the exception here is just for example, my point is that when you have multiple possibilities doing such thing with dictionary seems much cleaner than if/else, switch/case or multiconditional ternery operator

CodePudding user response：

I consider this pretty unreadable, but it avoids the nested ternary.

getResponse = int.TryParse(read, out var i) && i > 0 && i < 3 ? (bool)(2-i) : null;

Parse the string into an int, make sure it is the valid range, and then do some math so you can cast it to a bool. When casting an integer type to a bool, 0 means false, and non-zero means true.