Question

i have a code in c# like below

string s = new string('~',25);
int ind = 5;
s[ind] = 'A';

it gives an error

Property or indexer ‘string.this[int]’ cannot be assigned to — it is read

so what is the problem, and how can i fix it.

Answer 1

Strings are immutable – you can’t change an existing one.

Two options:

• Use StringBuilder, e.g.

  StringBuilder builder = new StringBuilder(new string('~', 25));
  builder[5] = 'A';
  string result = builder.ToString();
  

• Build a new string from a char array:

  char[] chars = new string('~', 25).ToCharArray();
  chars[5] = 'A';
  string result = new string(chars);
  

In both cases you could populate the mutable data without building a new string to start with if you want – that would involve more code, but would probably be more efficient.

Alternatively, you can take substrings and concatenate them together, as per another answer …there are basically lots of ways of tackling this. Which one is appropriate will depend on your actual use case.