C# Replace or Remove Char by Index

Strings in c# are immutable objects - it's not possible to replace or remove a char directly.

// Sample: We want to replace d with X
string somestring = "abcdefg";
somestring[3] = 'X';

Results in error: "Property or indexer cannot be assigned to - it is read only"
The solution is to create a new string with the given char replaced or removed.

Replace

There are multiple ways to achieve the replacement, e.g. using StringBuilder or String.ToCharArray();
Important: Don't forget to make sure the string is not empty or too short - otherwise you would get an exception!

// Sample: We want to replace 'd' with 'X' (index=3)
string somestring = "abcdefg";
StringBuilder sb = new StringBuilder(somestring);
sb[3] = 'X'; // index starts at 0!
somestring = sb.ToString();

or

// Sample: We want to replace 'd' with 'X' (index=3)
string somestring = "abcdefg";
char[] ch = somestring.ToCharArray();
ch[3] = 'X'; // index starts at 0!
string newstring = new string (ch);

Remove 1 Char at a given Index

// Sample: We want to remove 'd' (index=3)
// Don't forget to make sure the string is not empty or too short
string somestring = "abcdefg";
StringBuilder sb = new StringBuilder(somestring);
sb.Remove(3, 1);
somestring = sb.ToString();

Remove multiple Chars at a given Index

// Sample: We want to remove 3 chars "cde"(index=2-4)
// Don't forget to make sure the string is not empty or too short
string somestring = "abcdefg";
StringBuilder sb = new StringBuilder(somestring);
sb.Remove(2, 3);
somestring = sb.ToString();