如何将二元运算符分配给委托

Question

我如何将操作员分配给代表？int a = 5;int b = 2;Func<int, int, int> operation = /* int.operator+ or int.operator- */;int result = operation(a, b);我知道三种方法：Func<int, int, int> operation = (a, b) => a + b;这一个包装成一个额外的函数调用。Func<C, C, C> operation = (Func<C, C, C>)typeof(C).GetMethod("op_Addition").CreateDelegate(typeof(Func<C, C, C>));这个很可怕，不适用于基元。Expression<Func<C, C, C>> expression = (c, c2) => c + c2;BinaryExpression binaryExpression = (BinaryExpression)expression.Body;MethodInfo binaryExpressionMethod = binaryExpression.Method;Func<C, C, C> operation = (Func<C, C, C>)binaryExpressionMethod.CreateDelegate(typeof(Func<C, C, C>));这个更可怕，也不适用于基元。有优雅的方法吗？

Answer 1

您可以使用.Compilelambda 表达式的方法执行此操作：

Func<int, int, int> result;

var a = Expression.Parameter(typeof(int), "a");

var b = Expression.Parameter(typeof(int), "b");

var body = Expression.Add(a, b);

var lambda = Expression.Lambda<Func<int, int, int>>(body, a, b);

现在你lambda已经a + b准备好编译了：

result = lambda.Compile();

Console.WriteLine(result(5, 2)); // print 7