我完全在这一个丢失。我有一张code，做我需要在这样的实施是什么：

I am completely lost on this one. I have a piece of code that does what I need when implemented like this:

return filters.Add(m => m.Metadata.RecordId).IsEqualTo(1);

其中m为 TestObj 类对象和添加方法的参数是防爆pression＆LT; Func键＆LT; TestObj，布尔＆GT;＆GT;

where m is a TestObj class object and Add method's argument is Expression<Func<TestObj,bool?>>.

现在的问题是，我不能硬code m.Metadata.RecordId里面添加的，因为我来到这里就是告诉我有关应使用属性的字符串，在这种情况下，Metadata.RecordId 。我需要做的就是构建这样一个前pression这个字符串，会做同样的事情为m => m.Metadata.RecordId一样。我需要的是这样的：

Now the problem is that I cannot hardcode m.Metadata.RecordId inside Add, because what I get here is a string that informs me about the property that should be used, in this case "Metadata.RecordId". what I need to do is to construct such an expression with this string that will do the same thing as m => m.Metadata.RecordId does. I need something like this:

string propertyName = "Metadata.RecordId";
Expression expr = null;//create expression here somehow that will do the same as m => m.Metadata.RecordId
return filters.Add(expr).IsEqualTo(1); 

我该怎么办呢？

How do I do that?

推荐答案

我不知道究竟你想有作为输出（BOOL，INT和比较）， 但是，这应该让你在正确的轨道......

I'm not sure what exactly you want there as an output (bool, int and comparing), But this should get you on the right track...

public static void Test(string propertyPath)
{
    var props = propertyPath.Split('.');
    Expression parameter = Expression.Parameter(typeof(TestObj), "x");
    Expression property = parameter;
    foreach (var propertyName in props)
        property = Expression.Property(property, propertyName);
    Expression<Func<TestObj, int>> lambdaExpression =
        Expression.Lambda<Func<TestObj, int>>(property, parameter as ParameterExpression);
    Add(lambdaExpression);
}
static void Add(Expression<Func<TestObj, int>> paramExp)
{
    TestObj obj = new TestObj { Metadata = new Metadata { RecordId = 1, Name = "test" } };
    var id = paramExp.Compile()(obj);
}

和您还可以查看这个帖子Jon的这很好地描述了如何工作的？ Use反射来获取物业名称拉姆达EX pression

And you can also check this post of Jon's which nicely describes how that works... Use reflection to get lambda expression from property Name