A lot of times, we would like to get information about properties and fields in a class. This has lot of applications, in particular, provides a way to get rid of the magic strings spread throughout the program. Reflection used to the only method of choice to implement this feature, but with the introduction of expression trees, this becomes a lot more simple and elegant. A good introduction to the basics of expression trees can be found here.
Here is an implementation of Nameof using expression trees:
- publicstaticclassProperty<T>
- {
- publicstaticFunc<string> Nameof<TProperty>(Expression<Func<T, TProperty>> selector)
- {
- var expression = selector.Body asMemberExpression;
- if (expression == null)
- {
- thrownewArgumentException("'" + selector + "': is not a valid property or field selector");
- }
- return () => expression.Member.Name;
- }
- }
The Nameof implementation returns a function instead of the actual name. The Infoof implementation is very similar and can be achieved by changing the return value to PropertyInfo and using the following as the return value:
- return expression.Member asPropertyInfo;
The above implementation uses the type parameter T to define the containing class. This makes it easier to access the functions in a static context. An example usage is provided below:
- publicclassTestTarget
- {
- publicstaticreadonlyFunc<string> SampleProperty = Property<TestTarget>.Nameof(me => me.Sample);
- publicstring Sample { get; privateset; }
- }
The full source code along with the corresponding tests can be accessed as part of the core project here.
References :
