How to create lambda expression that returns object's property, having this property's name?

Question

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).IsEqua         


        

Answer 1

What about this call:

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

The method would have this signature:

public object ReflectionMagic(object source, string property);

If that would work, you could do something like this:

var propertyTree = property.Split('.');

foreach(var propertyName in propertyTree)
{
     var propInfo = source.GetType().GetProperty(propertyName);
     var source = propInfo.GetValue(source, null);
}

return source;

Be aware that any kind of argument and return value checks are missing and are left as an excercise to the reader.

Answer 2

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);
}

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