C# – check wheter Linq 2 SQL’s DataContext is tracking entities

clinq-to-sql

We want to throw an exception, if a user calls DataContext.SubmitChanges() and the DataContext is not tracking anything.

That is… it is OK to call SubmitChanges if there are no inserts, updates or deletes. But we want to ensure that the developer didn't forget to attach the entity to the DataContext.

Even better… is it possible to get a collection of all entities that the DataContext is tracking (including those that are not changed)?

PS: The last question I asked were answered with: "do it this way instead"… please don't 🙂

Best Answer

I don't think there are any public/protected methods that would let you get at this directly. You'd probably have to use reflection, like I did about 3 messages down here, looking at the ChangeTracker property of the Services. Very ugly, I'm afraid.

Related Solutions

Sql – Customizing Linq to Sql DataContext

Is there a simple way to add a property to Linq to Sql generated entity to reference its DataContext?

There is no simple way to achieve this.

C# – DbEntityValidationException – How to easily tell what caused the error

The easiest solution is to override SaveChanges on your entities class. You can catch the DbEntityValidationException, unwrap the actual errors and create a new DbEntityValidationException with the improved message.

Create a partial class next to your SomethingSomething.Context.cs file.
Use the code at the bottom of this post.
That's it. Your implementation will automatically use the overriden SaveChanges without any refactor work.

Your exception message will now look like this:

System.Data.Entity.Validation.DbEntityValidationException: Validation failed for one or more entities. See 'EntityValidationErrors' property for more details. The validation errors are: The field PhoneNumber must be a string or array type with a maximum length of '12'; The LastName field is required.

You can drop the overridden SaveChanges in any class that inherits from DbContext:

public partial class SomethingSomethingEntities
{
    public override int SaveChanges()
    {
        try
        {
            return base.SaveChanges();
        }
        catch (DbEntityValidationException ex)
        {
            // Retrieve the error messages as a list of strings.
            var errorMessages = ex.EntityValidationErrors
                    .SelectMany(x => x.ValidationErrors)
                    .Select(x => x.ErrorMessage);
    
            // Join the list to a single string.
            var fullErrorMessage = string.Join("; ", errorMessages);
    
            // Combine the original exception message with the new one.
            var exceptionMessage = string.Concat(ex.Message, " The validation errors are: ", fullErrorMessage);
    
            // Throw a new DbEntityValidationException with the improved exception message.
            throw new DbEntityValidationException(exceptionMessage, ex.EntityValidationErrors);
        }
    }
}

The DbEntityValidationException also contains the entities that caused the validation errors. So if you require even more information, you can change the above code to output information about these entities.

Best Answer

Related Solutions

Sql – Customizing Linq to Sql DataContext

C# – DbEntityValidationException – How to easily tell what caused the error

Related Topic