how to convert string to Button

Question

I know the id(string value) of button.Now i have to access the button depending on the string (id). I know can create the Id(String) of the button from database.Now i have to access(convert that to button) the button based on the created Id.There is complesary a Button with that created Id.But iam unable match boath of them in ASP.Net with C#.net.