Get an acronym from a string in C# using LINQ?

Question

Here is how I would write a function to make an acronym in Java style:

    string makeAcronym(string str)
    {
        string result = "";
        for (int i = 0; i < str.Length; i++)
        {
            if (i == 0 && str[i].ToString() != " ")
            {
                result += str[i];
                continue;
            }

            if (str[i - 1].ToString() == " " && str[i].ToString() != " ")
            {
                result += str[i];
            }
        }

        return result;
    }

Is there a more elegant way I can do it with LINQ, or using some built in C# function?

Answer 1

string makeAcronym(string str)
{
    return new string(str.Split(new [] {' '}, 
        StringSplitOptions.RemoveEmptyEntries).Select(s => s[0]).ToArray());
}

Answer 2

Here are a couple of options

A .NET 4 only option using string.Join:

 string acronym = string.Join(string.Empty,
      input.Split(new[] {' '}, StringSplitOptions.RemoveEmptyEntries).Select(s => s[0])
      );

In .NET 3.5 (or 4.0), you can do:

 string acronym = new string(input.Split(new[] {' '}, 
      stringSplitOptions.RemoveEmptyEntries).Select(s => s[0]).ToArray());

Another option (my personal choice), based on your original logic:

 string acronym = new string(
      input.Where( (c,i) => c != ' ' && (i == 0 || input[i-1] == ' ') )
      .ToArray()
    );

Answer 3

You can do this quite nicely using a Regex/Linq combo:

String
    .Join("",
        Regex
            .Matches("this is a test",@"(?<=^| )\w")
            .Cast<Match>()
            .Select(m=>m.Value)
            .ToArray()
    )

Answer 4

LINQ can work for this but generally I find it's better to build up string values using StringBuilder instance. This allows you to avoid unnecessary string allocations.

string makeAcronym(string str) { 
  var builder = new StringBuilder();
  for ( var i = 0; i < str.Length; i++ ) { 
    var c = str[i];
    if ( c == ' ' ) {
      continue;
    }
    if ( i == 0 || str[i-1] == ' ' ) {
      builder.Append(c);
    }
  }
  return builder.ToString();
}

Answer 5

You can use the LINQ Aggregate method to do this in a fairly elegant way.

Something like this:

private static string MakeAcronym2(string str)
{
    return str.Split(' ').Aggregate("", (x, y) => x += y[0]);
}

Answer 6

Here's a technique I haven't seen so far. It depends on the assumption that all the letters that should be in the acronym (and only those letters) are in upper-case in the string.

string MakeAcronym(string input)
{
    var chars = input.Where(Char.IsUpper).ToArray();
    return new String(chars);
}

// MakeAcronym("Transmission Control Protocol") == "TCP"