How to get names from expression property?

Question

Possible Duplicates:
Get method name and type using lambda expression
Can I use Expression<Func<T, bool>> and reliably see which properties are referenced in the Func<T, bool>?

Hi,

I want to have a method, which I can use like this

<% Html.TextBoxFor(x=>x.Property, Helper.GetAttributes<ViewModel>(x=>x.PropertyA)) %>

The method header looks like this

public static Dictionary<string, string> GetAttributeValues<T>(Expression<Func<T, object>> myParam)

but how do i find out the name of PropertyA? i need to do some checks before returning the right attributes. thanks in advance..

cheers

PS: thanks to driis post How to get names from expression property? i found the solution

it is

public static Dictionary<string, string> GetAttributeValues<T>(Expression<Func<T, object>> myParam)
{
    var item = myParam.Body as UnaryExpression;
    var operand = item.Operand as MemberExpression;
    Log.Debug(operand.Member.Name);
}

I think it should stay open. @GvS's answer is really good and applicable to doing this sort of work in an asp.net mvc application. None of the other questions we've marked as dupes have his answer. — John Farrell, Dec 29 '10 at 16:23
See also http://stackoverflow.com/questions/671968/retrieving-property-name-from-lambda-expression -- there's a gotcha if you want nested properties (i.e. `Thing1.Thing2` from `o => o.Thing1.Thing2` -- see [my attempt for an alternative](http://stackoverflow.com/a/17220748/1037948) — drzaus, Jun 20 '13 at 18:21

score 2 · Answer 1 · edited Feb 05 '13 at 15:25

2

Create an instance of a ModelMetadata class:

var data = ModelMetadata.FromLambdaExpression<T, object>(myParam);

And now you can get all the information you need, with respect to attributes used on your model:

var propName = data.PropertyName;
var label = data.DisplayName;

edited Feb 05 '13 at 15:25

Lightness Races in Orbit

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answered Dec 29 '10 at 14:03

GvS

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score 1 · Accepted Answer · answered Dec 29 '10 at 13:24

1

That could be:

string propertyName = ((MemberExpression) myParam.Body).Member.Name;

In production code, you should probably check the Expression type before the cast and throw an appropiate exception if the expression passed in is not MemberExpression.

answered Dec 29 '10 at 13:24

driis

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thanks for you fast response, but i get the error InvalidCastexception, cannot convert from "System.Linq.Expressions.UnaryExpression" to "System.Ling.Expressions.MemberExpression" – nWorx Dec 29 '10 at 13:27
thanks again,your hint with memberexpression has shown me the right way to solve this problem :-) i've updated my original post – nWorx Dec 29 '10 at 13:42

How to get names from expression property?

2 Answers2