Boolean Parse string

[davebythesea]

Hi folks,

Boolean.Parse("true") returns true, but what if you need to parse something
such as -

Boolean.Parse("(false && false) || (false || (true && true))");

Does something exist in the .NET framework to Parse this kind of string to
one final boolean result?

Thanks for any tips,
David

 

[Peter Bromberg [C# MVP]]

Dave,
I suppose I must be reallyreallydumb, but why on earth would you ever need
to do this? If its a legitimate business logic need, you could write a
method that would be capable of parsing these expressions and returning bool.
-- Peter
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[Bob Powell [MVP]]

The Parse methods for the common value types are there to convert a simple
string to the value. Evaluating expressions is not within its range of
capabilities.

You can write your own expression parser...

--
--
Bob Powell [MVP]
Visual C#, System.Drawing

Ramuseco Limited .NET consulting
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[Nicholas Paldino [.NET/C# MVP]]

David,

Yes, it's called the compiler. =)

If you really have a need for evaluating these kind of expression
strings, then you could use the CSharpCodeProvider class in the
Microsoft.CSharp namespace, creating the instance and populating it with
code (and with surrounding methods, classes as well, since you will have to
compile an assembly) compiling the code, and then executing it.

Ideally, you would create a class that implements an interface with a
method that returns a result. The body of that method's implementation
would be your expression.

Then, you would compile it all, create an instance of the type you
created/compiled, and then execute the method.

If the expressions is only ever going to be composed of the following
tokens:


(
)
false
true
||
&&

Then I would say it's not so difficult to create your own parser and you
can probably get away with using Expressions or some sort of dynamic code
generation using IL.

 

[Arne Vajhøj]

Boolean.Parse("true") returns true, but what if you need to parse something
such as -

Boolean.Parse("(false && false) || (false || (true && true))");

Does something exist in the .NET framework to Parse this kind of string to
one final boolean result?

That is not parsing. That is would be runtime expression evaluation.

It can be done. But it will have some overhead and some security
implications.

Are you sure that you need this ?

(I do have some code snippets if you really need it)

Arne

 

[davebythesea]

Hi folks,

Thanks for all your help. I'm going to have a think about all thats been
said and work out my approach. Once (if) I make some progress I may come back
and ask a couple more questions...

Cheers,
Dave