Check out example codes for "modificare una strinfa in c#". It will help you in understanding the concepts better.

Code Example 1

string phrase = "The quick brown fox jumps over the fence";

char[] phraseAsChars = phrase.ToCharArray();
int animalIndex = phrase.IndexOf("fox");
if (animalIndex != -1)
    phraseAsChars[animalIndex++] = 'c';
    phraseAsChars[animalIndex++] = 'a';
    phraseAsChars[animalIndex] = 't';

string updatedPhrase = new string(phraseAsChars);

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