c# Change the format of a string

Question

Edit:

Because of your responses I think I've asked the question wrong.

It's not that my solution doesn't work or isn't very clean. I'm interested if there is a general way, how you can foramt a string. Like you can do it with a int or other data types.

So I couldn't find one. But I hope there is one.

_{So that's the question I wanted to ask:}

Does C# provides a way to format strings, like it does for a int or other data types?

I'm looking for something like this:

myString.Format(myFormat);

or:

myFormattedString = String.Format(myString, myFormat);

And if the answer is no, it's also ok. I just want to know it. (And maybe someone else as well)

---

_{Original question:}

What's the best way to change the format of a string?

So I have a string that looks like this:

"123456789012345678"

And now I want that:

"12.34.567890.12345678"

---

I'm using this, but I don't find it very clean:

private string FormatString(string myString)
{
    return myString.Insert(2, ".").Insert(5, ".").Insert(12, ".");
}

---

Things I've tried:

// Too long.
private string FormatString(string myString)
{
    return myString.Substring(0, 2)
         + "."
         + myString.Substring(2, 2)
         + "."
         + myString.Substring(4, 6)
         + "."
         + myString.Substring(10, 8);
}

// Convertion from string -> long -> string.
private string FormatString(string myString)
{
    return String.Format("{0:##'.'##'.'######'.'########}", long.Parse(myString));
}

---

I'm looking for something like that:

private string FormatString(string myString)
{
    return String.Format("{0:##'.'##'.'######'.'########}", myString);
}

Answer 1

I don't see anything wrong with your code, but if you want a better matching system, you might want to consider regular expressions:

(\d{2})(\d{2})(\d{6})(\d{8})

And replace it with:

$1\.$2\.$3\.$4

(In action)

But my two cents: keep it like it is.

Answer 2

Well...when the framework does not provide what you want, you can always do it yourself.

I've made this method as a experiment. It can surely be optimized and is not fully tested, but it can give you a view of what you could do:

private string FormatString(string myString,string format)
{
    const char number = '#';
    const char character = '%';
    StringBuilder sb = new StringBuilder();

    if (format.Length < myString.Length) throw new Exception("Invalid format string");

    int i = 0;
    foreach (char c in format)
    {
        switch (c)
        {
            case number:
                if (char.IsDigit(myString[i]))
                {
                    sb.Append(myString[i]);
                    i++;
                }
                else
                {
                    throw new Exception("Format string doesn't match input string");
                }
                break;
            case character:
                if (!char.IsDigit(myString[i]))
                {
                    sb.Append(myString[i]);
                    i++;
                }
                else
                {
                    throw new Exception("Format string doesn't match input string");
                }
                break;
            default:
                sb.Append(c);
                break;
        }

    }
    return sb.ToString();
}

This method expects the format string to have either a # to denote digit, a % to denote a character, or any other character that would be copied literally to the formatted string.

Usage:

string test = FormatString("123456789012345678", "##.##.######.########");
//outputs 12.34.567890.12345678
string test = FormatString("12345F789012345678", "##.##.#%####.########");
//outputs 12.34.5F7890.12345678

Answer 3

If your string will always be a number then you can do it like this:

string stringData = "123456789012345678";
string dataInFormat = Convert.ToInt64(stringData).ToString(@"##\.##\.######\.########");

First convert string to long and then implement the format on that. In your case it would be like this:

private string FormatString(string myString)
{
    return Convert.ToInt64(myString).ToString(@"##\.##\.######\.########");
}