Handling huge string with stringbuilder in C#

Question

I want to replace the 2nd last character in the end of my string builder in an easy and efficient way (ie fast speed and less memory). The string will be about 200-300 mb I guess (not sure). How do I do it ? Will the answer change if the input string also has a newline at its end ?

Thanks.

Where is this string coming from? If its from a file.. I would suggest that you Seek to the end and replace the character by writing over the top of it. That saves a 300MB string being in memory.. — Simon Whitehead
– Simon Whitehead, Commented Oct 28, 2013 at 23:31

Reed Copsey · Accepted Answer · 2013-10-28 23:31:05Z

3

You can use StringBuilder.Chars to overwrite a specific char in the StringBuilder:

// For example, replace 'x' into the 2nd to last char
stringBuilder[stringBuilder.Length-2] = 'x';

answered Oct 28, 2013 at 23:31

Reed Copsey

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Nicholas Carey · Accepted Answer · 2013-10-28 23:32:41Z

3

StringBuilder uses an array of chars as its backing store. A simple

StringBuilder sb = new StringBuilder() ;
sb.Append( GetSomeEnormousString() ) ;

sb[ sb.Length - 2 ] = '*' ;

should do you.

Outside of any paging involved, it's a direct memory access.

answered Oct 28, 2013 at 23:32

Nicholas Carey

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