比较两个表达式的结果 [英] Compare the Results of Two Expressions

问题描述

我想比较两个表达式的结果，以确定它们是否相等.下面的代码可以编译，但是我得到一个例外，那就是参数数量不正确.考虑到这一点，我有两个问题.

I'd like to compare the results of two expressions to determine if they are equal.  The below code compiles but I get an exception that there is an incorrect number of parameters.  With that in mind I have two questions.

1. 比较两个表达式的正确Lambda表达式方法是什么?
2. 比较两个表达式的结果是否有更好/更简单的方法?

谢谢您的帮助.

瑞安

public static void SaveValue<T>(this Something first, ref Something second, Expression<Func<Something, T>> outExpr)
{
	Expression.Lambda<Func<Something, Something, bool>>(
		Expression.Equal(
			Expression.Invoke(outExpr, Expression.Parameter(typeof(Something))),
			Expression.Invoke(outExpr, Expression.Parameter(typeof(Something)))
	)).Compile()(first, second);				
}

public class Something
{
	public Something() {}
	public Something(string here) { Here = here; }
	public Something(int there ) { There = there; }
	public Something(string here, int there) { Here = here; There = there; }
        
	public string Here  { get; set; }
	public int    There { get; set; }
}

public class Program
{
	public static void Main(string[] args)
	{
		var mySomething = new Something("Hello");
		var mySomething3 = new Something("World", 3);

            	mySomething3.SaveValue(ref mySomething, s => s.Here);
            	mySomething3.SaveValue(ref mySomething, s => s.There);
            
            	Console.WriteLine(mySomething3.Here + ", " + mySomething3.There);
            	Console.WriteLine(mySomething.Here + ", " + mySomething.There);
        }
    }

推荐答案

您好，Ryan Sof 软件，

根据您的描述和相关代码，我创建了一个演示，它引发了异常.需要在名为的方法上添加参数 表达式 . Lambda. 请像这样修改代码:

Based on your description and related code, I create a demo and it throws an exception. which need to add parameters on your method named Expression.Lambda. please modify the code like this:

  public static void SaveValue<T>(this Something first, ref Something second, Expression<Func<Something, T>> outExpr)
        {
            ParameterExpression param1 = Expression.Parameter(typeof(Something));
            ParameterExpression param2 = Expression.Parameter(typeof(Something));

            var val1 = Expression.Invoke(outExpr, param1);
            var val2 = Expression.Invoke(outExpr, param2);
            var andExp = Expression.Equal(val1, val2);
            Expression.Lambda<Func<Something, Something, bool>>(
                 andExp, param1, param2
             ).Compile()(first, second);
        }

最诚挚的问候，

吴可乐

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