C # eval

Using System;
Using System. Collections. Generic;
Using System. LINQ;
Using System. text;

UsingSystem. codedom. compiler;
UsingSystem. reflection;

Namespace Eval_demo
{
///   <Summary>
/// Dynamic Evaluation
///   </Summary>
Public   Class Evaluator
{
///   <Summary>
/// Calculation result. If an expression error occurs, an exception is thrown.
///   </Summary>
///   <Param name = "statement"> Expression, such as "1 + 2 + 3 + 4" </Param>
///   <Returns> Result </Returns>
Public   Static   Object Eval ( String Statement)
{
Return _ Evaluatortype. invokemember (
" Eval " ,
Bindingflags. invokemethod,
Null ,
_ Evaluator,
New   Object [] {statement}
);
}

static Evaluator ()
{< br> /// construct the JScript compilation driver Code
codedomprovider provider = codedomprovider. createprovider ( " JScript " );

compilerparameters;
parameters = New compilerparameters ();
parameters. generateinmemory = true ;

Compilerresults results;
Results=Provider. compileassemblyfromsource (parameters, _ jscriptsource );

Assembly=Results. compiledassembly;
_ Evaluatortype=Assembly. GetType ("Evaluator");

_ evaluator = activator. createinstance (_ evaluatortype);
}

Private Static Object_ Evaluator= Null;
Private StaticType _ evaluatortype= Null;

///   <Summary>
/// JScript code
///   </Summary>
Private   Static   Readonly   String _ Jscriptsource =
@" Class Evaluator
{
Public Function eval (expr: string): String
{
Return eval (expr );
}
} " ;
}
}
Class Program
{
Static   Void Main ( String [] ARGs)
{
Console. writeline (Evaluator. eval ( " 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 " )); // 45
Console. writeline (Evaluator. eval ( " (10-2)/2 + 1) * 3 " )); // 15
}
}