Like you know how to open a solidworks assembly you need all the parts to it, but is that the same case with DXF files or can the other person just save it as DXF and give it to you?
The DXF would not need all (or any) parts. A DXF model or drawing is just a bunch of lines in 2D or 3D space.
Other formats may serve you better, depending on your actual need.
The DXF has no relations or references to parts in an assy. It's basically one sketch.
As Kelvin mentioned, use another format.
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