Dear All            My question is that there is command in auto cad through which (e.g we want to delete a line,for this we give erase command but for the first time this line will not delete and in 2nd attempt it will be deleted).Do you know about that command or settings in autocad

You can use the Express Tools OVERKILL command to delete duplicate objects that are overlapping, but if you just want to delete both objects then Window select them.