ASP.NET MVC 3代码优先使用空数据库

Question

I am new to ASP.NET MVC but have worked with RoR quite a bite so I am familiar with the MVC pattern.

I am curious about the possibilities when handling the database part when using the Code First approach. I was told by an ASP.NET developer colleague that you can create an empty database, that is a database with no tables and use EF Code First to create the tables in that empty database.

Is that correct?

I cannot find any tutorials/documentation on that particular approach anywhere. I have come across Code First approaches that start with an existing database and tables but not an existing database without tables.

I would love to know:

If this is possible. If it isn't, what's the next-closest approach?

Thanks

Thanks

Answer 1

Yes, it is possible by design. Here is the official tutorial

http://msdn.microsoft.com/en-us/data/jj591621.aspx

See section "Building an Initial Model & Database"

Note: If you database already exists, you can either name your dbcontext class as that database, or specify "Initial Catalog" in connection string to match your database.

Answer 2

At it's most basic level, you create a class to represent your table, a context class (derived from DbContext) and then execute commands in the Package Manager Console to create migrations/scripts and/or update the database schema directly (think of it as rake db migrate for EF Code First).

public class User
{
    public string Username {get;set;}
    public string Password {get;set;}
}

public class DatabaseContext : DbContext
{
    public DbSet<User> Users {get;set;}
}

Tools -> Library Package Manager -> Package Manager Console

Once the console window is open, make sure the project with your entity/context is selected in the "Default Project" dropdown at the top of the window and execute the following commands:

Add-Migration "Description of your migration"

This will create a migration class for you that represents your changes to the database since the last migration. If this is the first one (given that you're starting from an empty database), it will also generate a system table called "__MigrationHistory" which is used to track which migrations have already been applied to the database.

Update-Database -script

Executing Update-Database with the -script flag will generate a SQL script you can save/check in to source control if needed. If you'd prefer just to update the database itself without the script, just leave off the -script tag.

Be sure you have a connection string in web.config named the same thing as your context class ("DatabaseContext" in this example). This can point to your existing database but it will only manage/track changes to entities which are defined in your context class. I've found sometimes it's necessary to explicitly define the context when using the Add-Migration and Update-Database commands like so:

Add-Migration "Description of your migration" -connectionstringname "DatabaseContext"

Answer 3

You can simply create a class wich that is your table like

 public class Person{
public Guid id {get;set;};
public string Name {get;set;};
}

then you can add a ADO.NET data entity model type codefirst empty database then add the class into that database

add a ctor in db

static myDB(){
Database.setInitializer(new DropCreateDataBaseIfModelChanges<myDB>());
}


public virtual dbset<Person> People {get;set;};

after that your database will be create