Multipolygon shapefile - Border problem in ArcMap

I am analyzing a shapefile which shows a state of my country. The state shapefile also contains lots of different districs.

Now I want to have an border only for the state. But when I activate the border, ArcMap creates borders around the different districts, not around the whole state. But I want border around extent of the state, not district. How can I do it?

Thank you in advance!