Creating programmatically a new table using entities

ASP4student · January 26th, 2013, 10:28 PM

I wanted to create programmatically a new table, which will list the user names and emails of all the users. Here's the code:

Code:

var query =
           from u in myEntities.aspnet_Users
           join m in myEntities.aspnet_Membership
           on u.UserId
           equals m.UserId into userList
           select new
           {
             UserName = u.UserName,
             Email = u.aspnet_Membership.Email,
           };
      myEntities.SaveChanges();

I get no error when run the code, however, the userList table is not created.
Any help on this issue will be highly appreciated.
By the way, creating tables programmatically is not covered in this book. Is it covered in "Professional ASP.NET 4 in C# and VB"?

Imar · January 27th, 2013, 04:51 AM

Hi there,

This example does *not* create new tables; all it does is select new data, store it in a new, anonymous object that can then be used to display in the frontend. It's the equivalent of a JOIN in SQL that selects data from multiple tables but doesn't affect the database's structure.

You can't use EF to create new tables; based on the database schema some code needs to run first that generates .NET objects based on the underlying tables. You can create tables using Management Studio, DDL (e.g. CREATE TABLE statements) or programmatically using code. For that last option, take a look here: http://www.christophdebaene.com/blog...g-net-and-smo/ Just realize that this just creates a table; it doesn't make it available in your EF diagram; you have the run the Update wizard for that.

Cheers,

Imar

ASP4student · January 27th, 2013, 08:02 AM

The confirmation that "You can't use EF to create new tables" is very important.
I thought that the EF implemented all the basic features of SQL and tried to stay within EF with my entire code, but now I see that I have to mix in some SOL too.
Thank you very much.

Imar · January 27th, 2013, 08:13 AM

Not the Model First and Database First approaches of EF. EF also supports Code First that does create the database based on classes you create in your project (as opposed to the query you tried to use). However, that still requires you to write classes up front that are then turned into tables the first time you load an application with the changes. This is quite a different model, and requires quite a bit of knowledge on EF, Pocos and object modeling. For more info: http://msdn.microsoft.com/en-us/data/ee712907

Cheers,

Imar

ASP4student · January 27th, 2013, 12:19 PM

Thanks a lot for this information.