Does exist ORM / Framework that converts data automatically when I want to change column datatype in table?-Collection of common programming errors

In the .Net world I’ve had very good experience with LLBLGen Pro. It supports the generation of DDL scripts to migrate the underlying database to the updated entity definitions. Here is quick start guide that shows the overview of how this works, and here is documentation section for Model-First design process

You can either use it with its own runtime framework, or simply as a design tool for Entity Framework, NHibernate, or Linq to SQL.