Replace substrings with values from array

Question

I have a string like this:

string source = hello{1}from{2}my{3}world

And an array like this:

var valArray = new[] { "Val0", "Val1", "Val2", "Val3" };

I want to replace "{index}" substring with appropriate values from array.

I've already written the code, but it looks ugly

var valArray = new[] { "Val0", "Val1", "Val2", "Val3" };
var source = "hello{1}from{2}my{3}world";
var substr = source;
string pattern = $"{Regex.Escape(start)}{".+?"}{Regex.Escape(end)}";

foreach (Match m in Regex.Matches(source, pattern))
{
    var value = m.Groups[0].Value;
    var ind = Convert.ToInt32(m.Groups[0].Value.TrimStart(start.ToCharArray()).TrimEnd(end.ToCharArray()));
    substr = substr.Replace(value, valArray[ind]);
}
return substr;

Any tips how to get this solved?

Thanks!

Result string must be like this: "helloVal1fromVal2myVal3world" — Rasim Ismatulin, Mar 19 '16 at 14:44
if you source will be `hello{2}from{1}my{3}world` and `var valArray = new[] { "Val0", "Val1", "Val2", "Val3" };` what should be the output? — Ivan Gritsenko, Mar 19 '16 at 14:52

Gediminas Masaitis · Answer 1 · 2016-03-19T15:11:16.580

3

I think you're looking for String.Format:

string result = string.Format(source, valArray); // "helloVal1fromVal2myVal3world"

Just keep in mind that it's indexing from 0, not from 1.

edited Mar 19 '16 at 15:11

answered Mar 19 '16 at 14:43

Gediminas Masaitis

3,172
14
35

No code must automatic find and adjust all indexes {valArray} to valArray[index] – Rasim Ismatulin Mar 19 '16 at 14:47
3

Add `valArray.Cast – Ivan Gritsenko Mar 19 '16 at 14:50
1

@IvanGritsenko that isn't true `string.Format("hello{1}from{2}my{3}world", valArray);` gives `helloVal1fromVal2myVal3world` just fine – weston Mar 19 '16 at 15:08
@weston Yep, you're right. I just looked at Ivan's comment and thought "yeah, that makes sense". Now I properly tested it - an array of strings works just fine. – Gediminas Masaitis Mar 19 '16 at 15:12
@weston, Surprisely it is [not working](https://ideone.com/8oQt4G) on `int[]` or any other struct array. – Ivan Gritsenko Mar 19 '16 at 15:22
This is because of [array covariance](http://stackoverflow.com/a/35876845/1770952) for reference types. – Ivan Gritsenko Mar 19 '16 at 15:49

score 0 · Accepted Answer · answered Mar 19 '16 at 14:57

Use Regex.Replace(string input, string pattern, MatchEvaluator evaluator)

var valArray = new[] { "Val0", "Val1", "Val2", "Val3" };
var source = "hello{1}from{2}my{3}world";

string result = Regex.Replace(
    source,
    "{(?<index>\\d+)}",
    match => valArray[int.Parse(match.Groups["index"].Value)]);

score 0 · Answer 3 · answered Mar 19 '16 at 15:12

[Test]
public void SO_36103066()
{
    string[] valArray = new[] { "Val0", "Val1", "Val2", "Val3" };
    //prefix array with another value so works from index {1}
    string[] parameters = new string[1] { null }.Concat(valArray).ToArray(); 
    string result = string.Format("hello{1}from{2}my{3}world", parameters);
    Assert.AreEqual("helloVal0fromVal1myVal2world", result);
}

Replace substrings with values from array

3 Answers3