Remove tabulation or space of multiple lines in text

Question

You all probably know the keyboard shortcut (Shift + Tab) to remove tabulation or space of multiple lines in various text editors. I want to do this with my string in C#.

I know how to do it in a very unoptimized and not very error save way. But is there some "easy" way to do this e.g. with Regex, or some optimized code snipped to use out there?

But the point is to just remove one tabstop from the beginning.

Some hacked together idea of code:

string textToEdit = "Some normal text\r\n" +
                    "\tText in tab\r\n" + 
                    "    Text in space tab\r\n" + 
                    "  \t Text in strange tab\r\n" +
                    "\t\t\tMultiple tabs\r\n" +
                    "  Not quite a tab";
int spacesInTabstop = 4;

string[] lines = textToEdit.Split('\n');

foreach (string line in lines)
{
    int charPos = 0;
    for (int i = 0; line.Length > 0 && i < spacesInTabstop + charPos; i++)
    {
        if (line[charPos] == '\t')
        {
            line = line.Remove(0, 1);
            break; //Removed tab successfully
        }
        else if (line[charPos] == ' ')
        {
            line = line.Remove(0, 1); //Remove one of four spaces
        }
        else if (char.IsWhiteSpace(line[charPos]))
        {
            charPos++; //Character to ignore
        }
        else
            break; //Nothing to remove anymore
    }
}

textToEdit = string.Join("\n", lines);

The output should be:

Some normal text
Text in tab 
Text in space tab
 Text in strange tab
        Multiple tabs
Not quite a tab

`line.Trim()` removes all leading and trailing white spaces including tabs. — Olivier Jacot-Descombes, Mar 05 '19 at 21:01
Can you show the exact output you want, also is this only limited to 4? — TheGeneral, Mar 05 '19 at 21:06
Note that the `Remove` method returns the new string, it doesn't affect the original string. — Rufus L, Mar 05 '19 at 21:25
@OlivierJacot-Descombes The point is to remove just one tabstop from the beginning (Like with Shift + Tab) — Someone, Mar 05 '19 at 22:20
Whats the reasoning behind `Text in strange tab` having one space in front of it afterwards? also are you assuming tabs are 4 spaces? lastly, do you want to replace all tabs with space, or dont care — TheGeneral, Mar 05 '19 at 23:03
@MichaelRandall The "Text in strange tab" is just to test the code in a not that obvious condition. How many spaces a tab uses depends mostly on the editor and 4 or 8 spaces are most common. Lastly, I don't wont to replace any tabs with spaces, just remove them. — Someone, Mar 06 '19 at 16:33

Rufus L · Accepted Answer · 2019-03-05T23:07:27.750

Here's a method that does what I think your original code is intending to do, which is to remove up to 4 spaces from the start of the line, or a tab character, while ignoring other whitespace characters:

private static string RemoveLeadingTab(string input)
{
    var result = "";
    var count = Math.Min(4, input?.Length ?? 0);
    int index = 0;

    for (; index < count; index++)
    {
        if (!char.IsWhiteSpace(input[index])) break;
        if (input[index] == ' ') continue;

        if (input[index] == '\t')
        {
            index++;
            break;
        }

        if (char.IsWhiteSpace(input[index]))
        {
            result += input[index]; // Preserve other whitespace characters(?)
            if (input.Length > count + 1) count++;
        }
    }

    return result + input?.Substring(index);
}

In practice, it could be called like:

string textToEdit = "Some normal text\r\n\tText in tab\r\n    Text in space tab\r\n" +
                    "  \tText in strange tab\r\n\t\t\tMultiple tabs\r\n  Not quite a tab";

var result = string.Join(Environment.NewLine, textToEdit
    .Split(new[] {Environment.NewLine}, StringSplitOptions.None)
    .Select(RemoveLeadingTab));

Yeah, but you should add i-- before the continue to prevent character skipping. And i++ if a character is whitespace but should not be effected, to keep deleting 4 spaces after that. — Someone, Mar 05 '19 at 22:24
Oh, I see what you mean. We want to preserve other whitespace characters but still remove 4 spaces, even if some of them are after that whitespace character (right?). I updated the code sample. — Rufus L, Mar 05 '19 at 23:08

Remove tabulation or space of multiple lines in text

1 Answers1