Acting on the indentation of a c# multiline string

Question

I want to write some Html from c# (html is an example, this might be other languages..)

For example:

    string div = @"<div class=""className"">
                      <span>Mon text</span>
                   </div>";

will produce:

<div class="className">
            <span>Mon text</span>
         </div>

that's not very cool from the Html point of view...

The only way to have a correct HTML indentation will be to indent the C# code like this :

            string div = @"<div class=""className"">
    <span>Mon text</span>
</div>";

We get the correctly indented Html:

<div class="className">
    <span>Mon text</span>
</div>

But indenting the C# like this really broke the readability of the code...

Is there a way to act on the indentation in the C# language ?

If not, does someone have a tip better than :

string div = "<div class=\"className\">" + Environment.NewLine +
             "  <span>Mon text</span>" + Environment.NewLine +
             "</div>";

and better than

var sbDiv = new StringBuilder();
sbDiv.AppendLine("<div class=\"className\">");
sbDiv.AppendLine("    <span>Mon text</span>");
sbDiv.AppendLine("</div>");

---

What i use as a solution:

Greats thanks to @Yotam for its answer.

I write a little extension to make the alignment "dynamic" :

    /// <summary>
    /// Align a multiline string from the indentation of its first line
    /// </summary>
    /// <remarks>The </remarks>
    /// <param name="source">The string to align</param>
    /// <returns></returns>
    public static string AlignFromFirstLine(this string source)
    {
        if (String.IsNullOrEmpty(source)) {
            return source;
        }

        if (!source.StartsWith(Environment.NewLine)) {
            throw new FormatException("String must start with a NewLine character.");
        }

        int indentationSize = source.Skip(Environment.NewLine.Length)
                                .TakeWhile(Char.IsWhiteSpace)
                                .Count();

        string indentationStr = new string(' ', indentationSize);
        return source.TrimStart().Replace($"\n{indentationStr}", "\n");
    }

Then i can use it like that :

private string GetHtml(string className)
{
    return $@"
            <div class=""{className}"">
                <span>Texte</span>
            </div>".AlignFromFirstLine();
}

That return the correct html :

<div class="myClassName">
    <span>Texte</span>
</div>

One limitation is that it will only work with space indentation...

Any improvement will be welcome !

Answer 1

You could wrap the string to the next line to get the desired indentation:

    string div = 
@"
<div class=""className"">
    <span>Mon text</span>
</div>"
.TrimStart(); // to remove the additional new-line at the beginning

Another nice solution (disadvantage: depends on the indentation level!)

        string div = @"
        <div class=""className"">
        <span>Mon text</span>
        </div>".TrimStart().Replace("\n            ", "\n");

It just removes the indentation out of the string. make sure the number of spaces in the first string of the Replace is the same amount of spaces your indentation has.

Answer 2

I like this solution more, but how about:

string div = "<div class='className'>\n"
           + "    <span>Mon text</span>\n"
           + "</div>";

This gets rid of some clutter:

• Replace " inside strings with ' so that you don't need to escape the quote. (Single quotes in HTML appear to be legal.)
• You can then also use regular "" string literals instead of @"".
• Use \n instead of Environment.NewLine.

Note that the string concatenation is performed during compilation, by the compiler. (See also this and this blog post on the subject by Eric Lippert, who previously worked on the C# compiler.) There is no runtime performance penalty.

Answer 3

Inspired by trimIndent() in Kotlin.

This code:

    var x = @"
       anything
         you
       want
    ".TrimIndent();

will produce a string:

anything
  you
want

or "\nanything\n you\nwant\n"

Implementation:

public static string TrimIndent(this string s)
{
    string[] lines = s.Split('\n');

    IEnumerable<int> firstNonWhitespaceIndices = lines
        .Skip(1)
        .Where(it => it.Trim().Length > 0)
        .Select(IndexOfFirstNonWhitespace);

    int firstNonWhitespaceIndex;

    if (firstNonWhitespaceIndices.Any()) firstNonWhitespaceIndex = firstNonWhitespaceIndices.Min();
    else firstNonWhitespaceIndex = -1;

    if (firstNonWhitespaceIndex == -1) return s;

    IEnumerable<string> unindentedLines = lines.Select(it => UnindentLine(it, firstNonWhitespaceIndex));
    return String.Join("\n", unindentedLines);
}

private static string UnindentLine(string line, int firstNonWhitespaceIndex)
{
    if (firstNonWhitespaceIndex < line.Length)
    {
        if (line.Substring(0, firstNonWhitespaceIndex).Trim().Length != 0)
        {
            return line;
        }

        return line.Substring(firstNonWhitespaceIndex, line.Length - firstNonWhitespaceIndex);
    }

    return line.Trim().Length == 0 ? "" : line;
}

private static int IndexOfFirstNonWhitespace(string s)
{
    char[] chars = s.ToCharArray();
    for (int i = 0; i < chars.Length; i++)
    {
        if (chars[i] != ' ' && chars[i] != '\t') return i;
    }

    return -1;
}

Answer 4

If it is one long string then you can always keep the string in a text file and read it into your variable, e.g.

string text = File.ReadAllText(@"c:\file.txt", Encoding.UTF8);

This way you can format it anyway you want using a text editor and it won't negatively effect the look of your code.

If you're changing parts of the string on the fly then StringBuilder is your best option. - or if you did decide to read the string in from a text file, you could include {0} elements in your string and then use string.format(text, "text1","text2", etc) to change the required parts.