Try this: public class Team { public int TeamId { get; set;} public string Name { get; set; } public virtual ICollection<Match> HomeMatches { get; set; } public virtual ICollection<Match> AwayMatches { get; set; } } public class Match { public int MatchId { get; set; } public int HomeTeamId { get; set; } public … Read more
The difference is that in the first case the retrieved user is not tracked by the context so when you are going to save the user back to database you must attach it and set correctly state of the user so that EF knows that it should update existing user instead of inserting a new … Read more
You’re trying to update the record (which to me means “change a value on an existing record and save it back”). So you need to retrieve the object, make a change, and save it. using (var db = new MyContextDB()) { var result = db.Books.SingleOrDefault(b => b.BookNumber == bookNumber); if (result != null) { result.SomeValue … Read more
It is not about closing connection. EF manages connection correctly. My understanding of this problem is that there are multiple data retrieval commands executed on single connection (or single command with multiple selects) while next DataReader is executed before first one has completed the reading. The only way to avoid the exception is to allow … Read more
It’s not possible to create a many-to-many relationship with a customized join table. In a many-to-many relationship EF manages the join table internally and hidden. It’s a table without an Entity class in your model. To work with such a join table with additional properties you will have to create actually two one-to-many relationships. It … Read more
For those that are googling this and ended up here like me, this is how you currently do it in EF5 and EF6: context.Database.ExecuteSqlCommand(“TRUNCATE TABLE [TableName]”); Assuming context is a System.Data.Entity.DbContext Edit: Currently in net6.0 (dotnet 6 core) you can do the following: context.Database.ExecuteSqlRaw(“TRUNCATE TABLE [TableName]”); Or use the Async overload: await context.Database.ExecuteSqlRawAsync(“TRUNCATE TABLE [TableName]”); … Read more
You can extract all the information from the DbEntityValidationException with the following code (you need to add the namespaces: System.Data.Entity.Validation and System.Diagnostics to your using list): catch (DbEntityValidationException dbEx) { foreach (var validationErrors in dbEx.EntityValidationErrors) { foreach (var validationError in validationErrors.ValidationErrors) { Trace.TraceInformation(“Property: {0} Error: {1}”, validationError.PropertyName, validationError.ErrorMessage); } } }
You need to : Delete the state: Delete the migrations folder in your project; And Delete the __MigrationHistory table in your database (may be under system tables); Then Run the following command in the Package Manager Console: Enable-Migrations -EnableAutomaticMigrations -Force Use with or without -EnableAutomaticMigrations And finally, you can run: Add-Migration Initial
I ran into this and it was caused by the entity’s ID (key) field not being set. Thus when the context went to save the data, it could not find an ID = 0. Be sure to place a break point in your update statement and verify that the entity’s ID has been set. From … Read more
You can use the NotMapped attribute data annotation to instruct Code-First to exclude a particular property public class Customer { public int CustomerID { set; get; } public string FirstName { set; get; } public string LastName{ set; get; } [NotMapped] public int Age { set; get; } } [NotMapped] attribute is included in the … Read more