Reflection

Reflection is a powerful programming feature supported by .Net. The name describes exactly what it does - it reflects.

With reflection a program can read about itself and perform certain tasks for itself or the user.

One use of reflection is to discover the members of a class and act on those members. Perhaps the name of a member gets passed to a function that needs to be evaluated.

I ran across such a scenario in a program that filled up an ArrayList of records. I needed to perform some filtering on that ArrayList that with SQL was a little too complicated. I needed to do some intersections and minus operations that might have been easier to do with Oracle than with MS SQL but, I also wanted to see how it would be if I created my own little filtering language.

What I ended up using was the “GetProperty” method from the Type class, then use “GetValue” to find the value of a class member.

Here would be an example:

string str1 = rectype.GetProperty(field).GetValue(rc1[i], null).ToString();

“field” is just a string type containing the name of the member, and rc1 is a collection type containing an instance of a class having the members.

Although this type of reflection has quite a performance penalty especially over much iteration, it at least gets the job done.

With a little innovation one can create a nice flexible filtering program. Reflection programming makes it happen.