How to sort a Alphanumeric string with special characters in C# using Linq?

Question

How to sort a Alphanumeric string with special characters in C# using Linq? Order should be first special characters, then numbers and then alphabets.

Example :

Input - { Hello, #Test, @Red, &While, 123@Test, @123Test, %54Sun, Dom, Left }

Expected - { @123Test, %54Sun, @Red, #Test, &While, 123@Test, Dom, Hello, Left }

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Answer 1

You may use custom implementation of IComparer, then pass it to OrderBy call. E.g.:

public class SpecialCharactersNumbersLettersComparer : IComparer<string>
{
    private readonly IComparer<string> defaultComparer = StringComparer.InvariantCulture;
    
    private static int OrderOfChar(char ch)
    {
        if(Char.IsLetter(ch))
            return 2;
        if(Char.IsDigit(ch))
            return 1;
        return 0;
    }
    
    public int Compare(string left, string right)
    {
        if(string.IsNullOrEmpty(left)
          || string.IsNullOrEmpty(right)) {
            return defaultComparer.Compare(left, right);
        }
        
        var leftChar = left[0];
        var rightChar = right[0];
        var leftOrder = OrderOfChar(leftChar);
        var rightOrder = OrderOfChar(rightChar);
        
        if(leftOrder == rightOrder)
            return defaultComparer.Compare(left, right);
        
        if(leftOrder > rightOrder)
            return 1;
        return -1;
    }
}

public static List<string> SortSpecialCharactersNumbersAlphabet(IEnumerable<string> input)
{
    return input.OrderBy(_ => _, new SpecialCharactersNumbersLettersComparer())
        .ToList();
}

Used as:

Console.WriteLine(string.Join(", ",
    SortSpecialCharactersNumbersAlphabet(new [] {
    "Hello", "#Test", "@Red", "&While", "123@Test", "@123Test", "%54Sun", "Dom", "Left"})));

produces output:

@123Test, @Red, &While, #Test, %54Sun, 123@Test, Dom, Hello, Left