Viewstate has lots of advantages and as well as disadvantages, so you need to weigh carefully before making the decision to use it. view state doesnt require any server resources for its operation.
It is passed to the client during every postback as an hidden element. Since it is added with every page, it adds few Kbytes to the page.
This effects the loading of the page in the client. Other main problem with Viewstate is, since it is passed as plain text to the client.
Anybody can tamper this value, because of this you shouldnt store any important data in the viewstate. View state is one of the most important features of ASP.NET, not so much because of its technical relevance, but more because it makes the magic of the Web Forms model possible.
However, if used carelessly, view state can easily become a burden. Although ViewState is freely accessible in a hidden field called __VIEWSTATE, the view state information is not clear text. By default, a machine-specific authentication code is calculated on the data and appended to the view state string. The resulting text is then Base64 encoded only, but not encrypted.
In order to make the view state more secure, the ASP.NET @Page directive supports an attribute called EnableViewStateMac whose only purpose is detecting any possible attempt at corrupting original data.