Reflection vs. compiled expressions vs. delegates - Performance comparision

I'm currently working on an application which uses reflection to create a generic UI. Therefore I was interested in the performance impact of reflection. In this post I will do a comparison between the various possibilities to access a property.

The test setup

The following methods are used to access a property called Name in a class Person:

Access the property directly:

string name = p.Name;

Use reflection:

var property = p.GetType().GetProperty("Name");
string name = (string)property.GetValue(p, null);

This test is executed twice. First the PropertyInfo is created in every iteration. In the second test one instance is reused.

Use compiled expression:

ParameterExpression arg = Expression.Parameter(p.GetType(), "x");
Expression expr = Expression.Property(arg, "Name");

var propertyResolver = Expression.Lambda<Func<Person, object>>(expr, arg).Compile();

string name = (string)propertyResolver(p);

This test is also executed twice. First the Expression is created in every iteration. In the second test one instance is reused.

Use delegates:

ParameterExpression arg = Expression.Parameter(p.GetType(), "x");
Expression expr = Expression.Property(arg, "Name");

var propertyResolver = Expression.Lambda(expr, arg).Compile();

string name = (string)propertyResolver(p);

This seems to be the same as the test with the compiled expression. But there is a subtle change: The lambda is created without type information.

Each test is executed 1.000.000 times and the overall time is measured.

The results

Overview

Conclusion

Using the property is of course the fasted way to get the value of a (known) property. But also reflection is not that slow, especially when you reuse the PropertyInfo object.
Compiling an expression is a time consuming operation, but if you reuse the compiled expression the performance is equal to the regular property access. Compilation of expressions only makes sense, if you have to process a lot of objects.
Delegates are relatively slow, because type information is missing compared to compiled expressions.

Downloads

ReflectionPerformance.7z