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Memory Efficiency and Performance of String.Replace .NET Framework

Asked 2008-12-30T08:43:59.740
43
 string str1 = "12345ABC...\\...ABC100000"; 
 // Hypothetically huge string of 100000 + Unicode Chars
 str1 = str1.Replace("1", string.Empty);
 str1 = str1.Replace("22", string.Empty);
 str1 = str1.Replace("656", string.Empty);
 str1 = str1.Replace("77ABC", string.Empty);

 // ...  this replace anti-pattern might happen with upto 50 consecutive lines of code.

 str1 = str1.Replace("ABCDEFGHIJD", string.Empty);

I have inherited some code that does the same as the snippet above. It takes a huge string and replaces (removes) constant smaller strings from the large string.

I believe this is a very memory intensive process given that new large immutable strings are being allocated in memory for each replace, awaiting death via the GC.

1. What is the fastest way of replacing these values, ignoring memory concerns?

2. What is the most memory efficient way of achieving the same result?

I am hoping that these are the same answer!

Practical solutions that fit somewhere in between these goals are also appreciated.

Assumptions:

  • All replacements are constant and known in advance
  • Underlying characters do contain some unicode [non-ascii] chars
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if you want a built in class in dotnet i think StringBuilder is the best. to make it manully you can use unsafe code with char* and iterate through your string and replace based on your criteria

answered 2008-12-30T10:02:14.997

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