How to replace part of string by position?

Question

I have this string: ABCDEFGHIJ

I need to replace from position 4 to position 5 with the string ZX

It will look like this: ABC

Answer 1

With the help of this post, I create following function with additional length checks

public string ReplaceStringByIndex(string original, string replaceWith, int replaceIndex)
{
    if (original.Length >= (replaceIndex + replaceWith.Length))
    {
        StringBuilder rev = new StringBuilder(original);
        rev.Remove(replaceIndex, replaceWith.Length);
        rev.Insert(replaceIndex, replaceWith);
        return rev.ToString();
    }
    else
    {
        throw new Exception("Wrong lengths for the operation");
    }
}