How to choose between code First, Database first, and model first

Basic diagram of Code first, Database first, and model first:

1 ) Database First :

if the database already exists, you can use the VS automatic generation of data models, already relevant edmx Information

2 ) Model First

If you have not yet created a database, you can VS used in Model Design the database to generate mapping information through the designer ( edmx file) and generate the database automatically

3 ) Code First

automatically generate a database from a design data model without the need for additional edmx files, you can also generate data models from existing databases, database mappings, and do not require edmx file.

How to choose between code First, Database first, and model first