Fixed string concatenation

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Glenn - 04 Jul 2006 11:51 GMT

Hi

I realise StringBuilder is generally better for building strings
dynamically, but for a fixed string built over a number of lines, would the
compiler recognise that the following could be represented as a single
string and optimise out reallocations?

Example

string myString = "Blah";
myString += "Blah";
myString += "Blah";
myString += "Blah";
myString += "Blah";

Thanks

Glenn

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Phill W. - 04 Jul 2006 13:30 GMT

> would the compiler recognise that the following could be represented
> as a single string and optimise out reallocations?
[quoted text clipped - 4 lines]
> myString += "Blah";
> myString += "Blah";

Try it and see - the ILDasm utility is your friend in this - but my
/guess/ is that it won't.

You could, of course, rewrite the above as ...

string myString
= "Blah"
+ "Blah"
+ "Blah"
+ "Blah"
+ "Blah" ;

... which the compiler /does/ optimise - at least the equivalent
construct in VB.Net gets optimised so the C# compiler d*** well ought to
as well.... ;-)

HTH,
Phill W.

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Jon Skeet [C# MVP] - 04 Jul 2006 18:43 GMT

> I realise StringBuilder is generally better for building strings
> dynamically, but for a fixed string built over a number of lines, would the
[quoted text clipped - 8 lines]
> myString += "Blah";
> myString += "Blah";

I don't believe it does - but if you write it as:

string myString = "Blah"
+"Blah"
+"Blah"
+"Blah"
+"Blah";

then the concatenation will be done at compile time.

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Fixed string concatenation

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