我需要将复杂的表达式从字符串解析为 boolean 值。
它只能包含:
* boolean 值(真/假),
* 括号,
* AND/OR 操作数 (&&, ||)
例如:
bool.Parse("((true || false) && (false || false)) || (true || false)"
知道如何实现这一目标吗?
最佳答案
这是一个巧妙的评估器类,它为您提供 C# 代码中的 JScript.NET Eval 函数:
static public class Evaluator
{
private const string _jscriptSource =
@"package Evaluator
{
class Evaluator
{
public function Eval(expr : String) : String
{
return eval(expr);
}
}
}";
static private object _evaluator;
static private Type _evaluatorType;
[SuppressMessage("Microsoft.Performance", "CA1810:InitializeReferenceTypeStaticFieldsInline",
Justification = "Can't be done inline - too complex")]
static Evaluator()
{
InstantiateInternalEvaluator();
}
static private void InstantiateInternalEvaluator()
{
JScriptCodeProvider compiler = new JScriptCodeProvider();
CompilerParameters parameters;
parameters = new CompilerParameters();
parameters.GenerateInMemory = true;
CompilerResults results;
results = compiler.CompileAssemblyFromSource(parameters, _jscriptSource);
Assembly assembly = results.CompiledAssembly;
_evaluatorType = assembly.GetType("Evaluator.Evaluator");
_evaluator = Activator.CreateInstance(_evaluatorType);
}
static public int EvaluateToInteger(string statement)
{
string s = EvaluateToString(statement);
return int.Parse(s);
}
static public double EvaluateToDouble(string statement)
{
string s = EvaluateToString(statement);
return double.Parse(s);
}
static public decimal ForceEvaluateToDecimal(string statement)
{
decimal result;
bool s = Decimal.TryParse(statement, out result);
return result;
}
static public decimal EvaluateToDecimal(string statement)
{
string s = EvaluateToString(statement);
return decimal.Parse(s);
}
static public string EvaluateToString(string statement)
{
object o = EvaluateToObject(statement);
return o.ToString();
}
static public bool EvaluateToBool(string statement)
{
object o = EvaluateToObject(statement);
return (bool)o;
}
static public object EvaluateToObject(string statement)
{
try
{
return _evaluatorType.InvokeMember(
"Eval",
BindingFlags.InvokeMethod,
null,
_evaluator,
new object[] {statement}
);
}
catch (Exception)
{
InstantiateInternalEvaluator();
return null;
}
}
}
然后您就可以调用 Evaluator.EvaluateToBool(string)。从现有项目中提取,因此您可能需要进行调整!
关于.net - 在 .NET 中将复杂的 boolean 条件从字符串转换为 boolean 值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/690017/