Are you creating a 'Master Model' Drawing where the Drawing file and the Model File are different part files? If so, is the Sketch in the Model file? Or are you creating a Sketch in one of the Drawing views?
the model file and the drawing file is linked.
i created some simple sketch in the model and want them to show up in a projection view in drafting mode. so whenever i make some changes to those sketch in the model, i want those sketches can update themselves when i click the "Update" in the drafting mode
You will have to make sure that the Sketch is part of the 'Model' Reference Set. This is not done automatically so you will need to manually add the sketch to the Reference Set by going to the...
Format -> Reference Sets...
...and selecting the 'Model' Reference Set in the list and then selecting the Sketch.
Alternate, we can move sketch to a particular layer and use Layer Visible in View command show/hide that particular layer in required drafting view.