Creating a More Complex Data Model for an ASP.NET MVC Application (4 of 10)http://asp.netMon, 17 Oct 2011 11:28:48 GMTumbracoComments for Creating a More Complex Data Model for an ASP.NET MVC Application (4 of 10)enComment Posted by mejamzhttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationFri, 22 Apr 2011 02:12:35 GMT00000000-0000-0000-0000000012931I had some trouble with issues with the error mentioned in this post and the resolve mentioned worked the couple of time. I finally had to save all and close VS 2010. Once reopend, everythng was fine, even the column name changed to firstName finally :) So far... nice

]]>Comment Posted by praveen.prasadhttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationMon, 25 Apr 2011 15:16:11 GMT00000000-0000-0000-0000000012962how to generate entity diagram??

]]>Comment Posted by tdykstrahttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationMon, 25 Apr 2011 19:18:35 GMT00000000-0000-0000-0000000012966@praveen.prasad - I used the Database First designer to create an entity diagram using the database created by Code First. There isn't a tool available yet to create a diagram directly from the Code First code.

]]>Comment Posted by roux76http://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationWed, 27 Apr 2011 11:55:54 GMT00000000-0000-0000-0000000012999Is there a way to override the Icollection navigation property looking for the foreign key name to be the same as the table primary key? For example in the Student / Enrollment scenario, what would happen if the field within the Enrollments table was called something other than StudentID?

]]>Comment Posted by tdykstrahttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationThu, 28 Apr 2011 19:23:20 GMT00000000-0000-0000-0000000013016You can name the field whatever you want and add a [ForeignKey("Student")] attribute or use a fluent API mapping call to do the same thing. There are links at the end of the last tutorial to documents with more info on both attributes and mapping API.

]]>Comment Posted by tobias123http://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationFri, 29 Apr 2011 11:23:13 GMT00000000-0000-0000-0000000013026the modeling in OnModelCreating should be explained a bit more in depth

]]>Comment Posted by tdykstrahttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationSat, 30 Apr 2011 10:56:42 GMT00000000-0000-0000-0000000013041@tobias123 - At the end of the last tutorial, one of the links is to a blog post with more information about the mapping fluent API. Is there something in particular that you are looking for here that's missing but should be present for a basic intro?

]]>Comment Posted by tobias123http://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationTue, 03 May 2011 12:11:25 GMT00000000-0000-0000-0000000013059@tdykstra: can you please explain each of these statements:

no1:

modelBuilder.Entity<Instructor>()

.HasOptional(p => p.OfficeAssignment).WithRequired(p => p.Instructor);

An Instructor has an optional/nullable Property OfficeAssignment!??

Whats the WithRequired for? How to "read" this?

No2:

modelBuilder.Entity<Course>()

.HasMany(c => c.Instructors).WithMany(i => i.Courses)

.Map(t => t.MapLeftKey("CourseID")

.MapRightKey("InstructorID")

.ToTable("CourseInstructor"));

How to "read" this? many-to-many mapping.

One course can have many instructors!? <- indicated by the HasMany function AND thereby switching the "subject" (from Course to Instructors)!?

So that then one instructor can have many courses!? Indicated by the WithMany method but this time WITHOUT(?) switching the subject (back from instructor to course again)!??

What key should be on the left and what on the right side? Does this matter anyway in the Map method?

.Map(t => t.MapLeftKey("CourseID")

.MapRightKey("InstructorID")

thanks, tobi

]]>Comment Posted by tdykstrahttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationThu, 05 May 2011 12:02:42 GMT00000000-0000-0000-0000000013080@tobi - See my blog post for more info about these API call and links to the API reference documentation: blogs.msdn.com/

In the tutorial I added a link to the blog post right after the part where it talks about the method calls also.

]]>Comment Posted by tdykstrahttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationThu, 05 May 2011 16:15:43 GMT00000000-0000-0000-0000000013082That was the wrong link, here's the correct one: blogs.msdn.com/

]]>Comment Posted by assafg2http://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationWed, 11 May 2011 04:33:12 GMT00000000-0000-0000-0000000013130Hello, there is a different between the code you have wrote and the explanation

var courses = new List

{

new Course { CourseID = 1050, Title = "Chemistry", Credits = 3, DepartmentID = 3, Instructors = new List() },

...

};

vs

new Course { CourseID = 1050, Title = "Chemistry", Credits = 3, DepartmentID = 3, Instructors = new List<Instructor>() },

new Course { CourseID = 4022, Title = "Microeconomics", Credits = 3, DepartmentID = 4, Instructors = new List<Instructor>() },

]]>Comment Posted by emersionhttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationWed, 11 May 2011 05:58:53 GMT00000000-0000-0000-0000000013131Required(ErrorMessage = "First name is required.")]

How to make above messages language specific ? e.g. if I want to give message based on user's selected language then how it can be achieved ?

]]>Comment Posted by tdykstrahttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationWed, 11 May 2011 17:04:14 GMT00000000-0000-0000-0000000013136See this MSDN page and these StackOverflow threads:

msdn.microsoft.com/

stackoverflow.com/

stackoverflow.com/

]]>Comment Posted by hsharberhttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationSat, 28 May 2011 20:23:01 GMT00000000-0000-0000-0000000013304For the entity Enrollment, why do you include the foreign keys as well as the navigation properties for Course and Student? Wouldn't the navigational property be able to provide its key?

I can see that you've done this for other entities whenever there is a one-to-one relationship. Does it have a use that the navigational property doesn't provide?

Thanks for the series.

]]>Comment Posted by tdykstrahttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationTue, 31 May 2011 11:34:34 GMT00000000-0000-0000-0000000013340@hsharber - See the section on Foreign Key Associations in www.asp.net/

In web applications it is often much easier to work with foreign keys than it is to work with navigation properties; you often have a foreign key value and can insert or update an entity using that without having to retrieve the entity that the foreign key refers to in order to use the navigation property to establish the relationship.

]]>Comment Posted by godspeed1208http://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationWed, 24 Aug 2011 18:04:37 GMT00000000-0000-0000-0000000014049Thanks for the help,was having trouble with www.enticemarketing.com

]]>Comment Posted by wrlucashttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationThu, 01 Sep 2011 18:55:32 GMT00000000-0000-0000-0000000014106I comment out this code in the Global.asax.cs file

//Database.SetInitializer<SchoolContext>(new SchoolInitializer());

Once I have created the database I want to be able to work with as if it were the production version.

But simply adding this attribute:

[MaxLength(50)]

public string LastName { get; set; }

To the LastName property in the Student class, I get the below error when executing this code in the Index method of the Student Controller:

var students = from s in db.Students

select s;

Why is this even an issue. The structure of the database has not changed -- just the business rule for LastName.

System.InvalidOperationException was unhandled by user code

Message=The model backing the 'SchoolContext' context has changed since the database was created. Either manually delete/update the database, or call Database.SetInitializer with an IDatabaseInitializer instance. For example, the DropCreateDatabaseIfModelChanges strategy will automatically delete and recreate the database, and optionally seed it with new data.

Source=EntityFramework

StackTrace:

at System.Data.Entity.CreateDatabaseIfNotExists`1.InitializeDatabase(TContext context)

at System.Data.Entity.Internal.InternalContext.<>c__DisplayClass5.<PerformDatabaseInitialization>b__3()

at System.Data.Entity.Internal.InternalContext.PerformInitializationAction(Action action)

at System.Data.Entity.Internal.InternalContext.PerformDatabaseInitialization()

at System.Data.Entity.Internal.LazyInternalContext.<InitializeDatabase>b__4(InternalContext c)

at System.Data.Entity.Internal.RetryAction`1.PerformAction(TInput input)

at System.Data.Entity.Internal.LazyInternalContext.InitializeDatabaseAction(Action`1 action)

at System.Data.Entity.Internal.LazyInternalContext.InitializeDatabase()

at System.Data.Entity.Internal.InternalContext.Initialize()

at System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type entityType)

at System.Data.Entity.Internal.Linq.InternalSet`1.Initialize()

at System.Data.Entity.Internal.Linq.InternalSet`1.get_InternalContext()

at System.Data.Entity.Infrastructure.DbQuery`1.System.Linq.IQueryable.get_Provider()

at System.Linq.Queryable.Select[TSource,TResult](IQueryable`1 source, Expression`1 selector)

at ContosoUniversity.Controllers.StudentController.Index(String sortOrder, String currentFilter, String searchString, Nullable`1 page) in D:\Visual Studio 2010 Projects\MVC\ContosoUniversity\ContosoUniversity\Controllers\StudentController.cs:line 43

at lambda_method(Closure , ControllerBase , Object[] )

at System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters)

at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)

at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)

at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClass15.<InvokeActionMethodWithFilters>b__12()

at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)

InnerException:

]]>Comment Posted by wrlucashttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationThu, 01 Sep 2011 20:27:40 GMT00000000-0000-0000-0000000014108This is a great tutorial. But how about one that addresses database first but not in the clunky way I have seen every other tutorial do it. Either they generate a conceptual model or it is just a comment after a tutorial like this. There must be elegant solutions equal to Code First. How often does the opportunity for code first come up? Zero, in my life.

]]>Comment Posted by TheGDizzohttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationFri, 02 Sep 2011 15:24:38 GMT00000000-0000-0000-0000000014111In the tutorial series soo far... I have not picked-up on the meanings of some of the piece-parts (in the parenthesis) of the "Fluent API" coding you've shown.

For example, in :

protected override void OnModelCreating(DbModelBuilder modelBuilder)

{

modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();

modelBuilder.Entity<Instructor>()

.HasOptional(p => p.OfficeAssignment).WithRequired(p => p.Instructor);

modelBuilder.Entity<Course>()

.HasMany(c => c.Instructors).WithMany(i => i.Courses)

.Map(t => t.MapLeftKey("CourseID")

.MapRightKey("InstructorID")

.ToTable("CourseInstructor"));

modelBuilder.Entity<Department>()

.HasOptional(x => x.Administrator);

}

What the heck do the "p", "c", "t", and "x" correlate too in the statements which describe .HasMany( ) and .WithMany( ) relationships? They seem to have no ryhme-or-reason and are just mnemonic placeholders you've chosen off the top of your head I take it?

Also... if you could write a little blurb on what the English sentence translation of what (for example) "(c => c.Instructors)" is stating... specifically the "=>" symbol... I'd be very appreciative. I hate not knowing what some of the syntax pieces are saying to me.

Also... on the "Fluent API" link you provided... the code samples and description of them had their width cutoff with no way to scroll or stretch the screen to be able to view what I was missing (most likely because my default Font size I bumped-up one notch bigger the other day since doing soo much reading thru these tutorials)

Please let me know if further clarification is required.

]]>Comment Posted by tdykstrahttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationThu, 08 Sep 2011 17:07:06 GMT00000000-0000-0000-0000000014155@wrlucas - The first two of the three tutorial series at asp.net/ are database first; specifically how would you change the approach in those tutorials?

]]>Comment Posted by tdykstrahttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationThu, 08 Sep 2011 17:27:43 GMT00000000-0000-0000-0000000014156@TheGDizzo - Great questions. These are lambda expressions, and the best explanation of lambdas available on the web that I've seen is at:

www.c

This is a book chapter that starts out on delegates -- to go straight to lambdas if you're already familiar with delegates, anonymous methods, etc., go to the 5th page.

Thanks for the note about the code font size on the Fluent API code block; I've changed it to a smaller font and added line breaks.

]]>Comment Posted by controlaltdeletehttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationSun, 02 Oct 2011 03:06:17 GMT00000000-0000-0000-0000000014313I created classes as given in the tutorial, yet there was no change in School.sdf. In schoolcontext and schoolinitializer i am getting these errors:

'ContosoUniversity.Models.Course' does not contain a definition for 'DepartmentID' and 'ContosoUniversity.Models.Course' does not contain a definition for 'Instructors'. Please help me.

]]>Comment Posted by tdykstrahttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationThu, 06 Oct 2011 14:32:40 GMT00000000-0000-0000-0000000014341@controlaltdelete - The quickest way to find where you might have missed a step is to download the completed project (see download links at the top of the tutorial) and compare its files with what you have created by following the tutorial.

]]>Comment Posted by maximusmdhttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationMon, 10 Oct 2011 11:35:38 GMT00000000-0000-0000-0000000014377What if I did not use the OnModelCreating method? for instance, would it be ok to create a table CourseInstructor and create the associate links between Course and Instructorby using a EDMX file?

]]>Comment Posted by ManAtArms_Kalhttp://asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-applicationMon, 17 Oct 2011 11:28:48 GMT00000000-0000-0000-0000000014437In "Entity Diagram Showing Relationships" chapter,you says :"zero-or-one-to-many relationship line (0..1 to *) between the Department and Instructor entities."

and then ,in "Customizing the Database Context" chapter,you says: "•A one-to-zero-or-one relationship between the Department and Instructor tables, represented by the Department.Administrator navigation property"

This is why? Would you help me understand above different.

]]>