If you're talking about sweet corn for eating, then no.

First, If it's an improvement on regular corn then it probably is cross pollinated and seeds from that will not necessarily produce the same results as the parent seed.

Second, to make viable seed the cob has to stay on the plant until it is well past the stage that it is in for eating. Sweet corn is picked the milk stage, or slightly after which is why it's so sweet, soft and juicy.

To grow viable seed, the cob has to be on the plant past the milk stage, past the dough stage, past the dent stage, then longer until the kernel is dry enough to store over winter without molding or decaying.

If a cob is picked too soon, the result will be a shriveled up kernel with a thin skin and not much inside which may even be fermented. So even if dried, it may not be a viable seed. There may be some variance to what I described but not enough so you can pick sweet corn, let it dry and have ripened seed that will produce the same thing as the parent seed or even be viable at all.

Why don't you just ask the seller what the name of the corn is you are buying and then buy that type of seed for yourself to plant in your garden? There are many great types of sweet corn seed for sale on the open market for anyone to buy.

The biggest factor to producing great sweet corn is knowing how to grow good corn in the first place and then to know just the right time to pick it so it's at it's height of sweetness and flavor. And even then to promptly cook the corn soon after picking so it doesn't loose any flavor or sweetness due to the beginnings of fermentation.