Replace string only when 100% matched

Question

Just wandering, how could I replace a string only when 100% matched in c# .net?For example, I have the following string:

StringBuilder a = new(StringBuilder);     
a = "ABC-1 ABC-1.1 ABC-1.1~1"

I'm using the following scrip to replace the string:

a.Replace("ABC-1", "ABC-2");

At the moment the output is like the following :

ABC-2 ABC-2.1 ABC-2.1~1

Instead, I'm looking for the output is like:

ABC-2 ABC-1.1 ABC-1.1~1

Does anyone know how can I do it?

What makes something 'complete'? Do you mean 'a word has to have spaces around it (or be at the start or end of the string) - and I want to match the entire word'? If so, use `string.Split`. Iterate over the array and replace entries in the array where they are an exact match (`==`). Then `string.Join` it back together. — mjwills, Feb 06 '19 at 04:43

score 5 · Answer 1 · answered Feb 06 '19 at 04:39

5

This may help:

var a = "ABC-1 ABC-1.1 ABC-1.1~1";
var result = String.Join(" ", a.Split(' ').Select(x=>x=="ABC-1"? "ABC-2":x));

Result:

"ABC-2 ABC-1.1 ABC-1.1~1"

answered Feb 06 '19 at 04:39

Mehrdad Dowlatabadi

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score 3 · Answer 2 · answered Feb 06 '19 at 04:40

The "duplicate" being linked to would be a good solution if your input didn't have punctuation in it that signaled the end of a word. So the Regex in that thread doesn't work as-is.

You should be able to use a negative lookahead though.

var a = "ABC-1 ABC-1.1 ABC-1.1~1";

a = Regex.Replace(a, @"\bABC-1\b(?!\S)", "ABC-2");

Console.WriteLine(a);  // ABC-2 ABC-1.1 ABC-1.1~1

It basically asserts that the character after the search term is not a non-whitespace character (but also matches if it's the end of the string).

score 1 · Answer 3 · answered Feb 06 '19 at 17:09

If you want to replace only the first ocurrence, this method can help you:

public static string ReplaceFirst(this string original, string oldValue, string newValue)
{
    var index = original.IndexOf(oldValue);
    if (index >= 0) {
        var prev = original.Substring(0, index);
        var after = original.Substring(index + oldValue.Length);
        return prev + newValue + after;
    }
    return original;
}

score 0 · Answer 4 · answered Feb 06 '19 at 04:58

To match exact word use regex @"(^|\s)ABC-1.1(\s|$)";

string a = "ABC-1 ABC-1.1 ABC-1.1~1";
    string pattern  = @"(^|\s)ABC-1.1(\s|$)";
    string replace =  Regex.Replace(a, pattern , " test ");

    Console.WriteLine(replace);

output ABC-1 test ABC-1.1~1

Replace string only when 100% matched

4 Answers4