StringBuilder

If you need to append a series of strings to another string in a loop, you can save CPU cycles by using a StringBuilder. This is because string += concatenations create a new string on the heap, which takes time.

Here is some test code using regular string concatenations:

for (int i = 0; i < 1000; i++)
{
string s = "";
for (int j = 0; j < 20; j++)
{
s += "aabbcc";
}
}

And here is the equivalent using a StringBuilder:

for (int i = 0; i < 1000; i++)
{
string s = "";
StringBuilder sb = new StringBuilder();
for (int j = 0; j < 20; j++)
{
sb.Append( aabbcc );
}
s = sb.ToString();
}

Both bits of code append a string to another string 20 times. They repeat doing that a 1000 times to get some meaningful numbers. The overhead of creating the StringBuilder and getting its contents into a string is contained within the 1000 times loop.

On my machine, the results were:

Test	Time taken (ticks)
1000 * 20 concatenations	29474
1000 * 20 StringBuilder appends	11906

This shows...