Could you tell me please which option you prefer? I created the sentence in my head. Can you show me what you have done/did?
Context: I want to ask someone to show me the result of his work.
I would prefer the present perfect.
I agree with Julian. It depends on the context. If I were standing in front of someone who had just completed a task I'd use the present perfect. if I wanted to see the results of a task which he/she had completed previously I'd use the past tense.
However, in order to decide whether to use the present perfect or the past simple you need to know how those two tenses are used, Slovac (there are plenty of threads which discuss the difference).
Was the work done recently? Was the work done a long time ago? Is the work completed? Your simple sentence and limited context can still allow the use of either tense.
<<Cross posted with london calling: the forum guidelines requiring the inclusion of context are in place precisely because of this kind of issue. My first posts were a less direct way of reminding the OP of the importance >>