将两个 lambda 与表达式相乘

Question

基本上，我试图将两个 lambda 表达式与 class 表达式相乘，但我什至无法构建，也找不到相关文档。这是我的代码：

var f = x=>x+2;
var g = x=>x+3;
var argX = Expression.Parameter(typeof(double), "x");
var fg = Expression.Multiply(Expression.Constant(g, typeof(Func<double, double>)), Expression.Constant(f, typeof(Func<double, double>)));
//var fg = Expression.Multiply(Expression.Constant(g),Expression.Constant(f));
var lambda = Expression.Lambda<Func<double, double>>(f3, argX);
return lambda.Compile();

Answer 1

为此，只需将 f 和 g 也定义为 Expression：

var argX = Expression.Parameter(typeof(double), "x");

var f = Expression.Add(argX, Expression.Constant(3.0)); // applies to x => x + 3
var g = Expression.Add(argX, Expression.Constant(2.0)); // applies to x => x + 2
var fg = Expression.Multiply(f, g); // applies to f(x) * g(x)
var lambda = Expression.Lambda<Func<double, double>>(fg, argX);

现在这样称呼它：

var r = lambda.Compile()(1);

其中 returns 12。

Answer 2

你想要这样的东西吗：

Expression<Func<double,double>> f = x => x + 2;
Expression<Func<double,double>> g = x => x + 3;

var param = Expression.Parameter(typeof(double));
var invokeF = Expression.Invoke(f, param);
var invokeG = Expression.Invoke(g, param);

var mult = Expression.Multiply(invokeF,invokeG);

var lambda = ((Expression<Func<double, double>>)Expression.Lambda(mult, param)).Compile();

如果我这样称呼它：

lambda(3);

我得到 30 个有效答案。

将两个 lambda 与表达式相乘

Multiply two lambda with Expression

c#

performance

lambda

linq-expressions