Selective disabling of lazy loading with Database First method

Question

I am not interested in disabling lazy loading for the entire context. I want only to selectively disable lazy loading for a few key navigational properties.

With the Code First method, I understand how to selectively disable lazy loading:

public virtual Person Requestor { get; set; } //lazy loading enabled
...
public Person Requestor { get; set; } //lazy loading disabled

However with the Database First method, this is code generated from a template so this modification is going to be lost on the next regeneration.

Is there a way to modify the model or template generator for such selective disabling of lazy loading?

Surprisingly there is no way to statically define this for a navigation property in the edmx designer. An effective, but far more elaborate way would be to modify the t4 template to not write the virtual modifier for specific properties in specific classes. — Gert Arnold
– Gert Arnold, Commented Jun 8, 2013 at 20:59
@GertArnold I ended up doing two things. Modyifying the t4 template and the accepted answer. — Sportball
– Sportball, Commented Jul 11, 2013 at 14:20

Quinton Bernhardt · Accepted Answer · 2013-07-14 11:48:09Z

1

I don't know of a way. But if you are going to use the Entity code generator you could build in a warning system so that when the code is re-generated you get notified immediately (depending on your build strategy).

So what I would do is for the selected entites, say the entity is Request and the property in question is Requestor then write a test to assert that the property is NOT virtual

            [TestMethod()]
            public void RequestPropertyRequestor_MustNotBeVirtual() {

                PropertyInfo[] properties = typeof(Request).GetProperties()
                    .Where(p => p.GetGetMethod().IsVirtual).ToArray();
               Assert.AreEqual(0, properties.Count(p => p.Name == "Requestor"), "Model Code Regenerated - change the Request Entity");
            }

Not sure of the accuracy of the reflection code but you get what i mean. This way when the entities are regenerated and you have amended the code, the test fails. early warning system

OR

you could turn off code generation and use POCO's.

Recommended Change

If you don't wanna turn off code gen then modifying the T4 template is the way to go. Just

set the "Code Generation Stategy" to None in the properties of the EDMX designer so that the default generation doesn't occur. This results in no derived DbContext or entity classes
in the EDMX designer, right click on the drawing surface and select "Add Code Generation Item". There should be generators listed there, if not just install one through NuGet. Select the EF5 DbContext one.
Find the T4 template for the entity generation and modify.

edited Jul 14, 2013 at 11:48

answered Jun 8, 2013 at 16:24

Quinton Bernhardt

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2 Comments

Sportball Over a year ago

A very creative approach. In the absence of coming up with something better, this is a viable (though not at all desirable) solution.

Quinton Bernhardt Over a year ago

You're right, but i couldn't resist demonstrating another use for unit tests, albeit not the traditional use for it. The way to go IMHO is changing the T4 template. See my edit on how to hook it up. I changed mine, for example, to generate the entity class name as <EntityName>Generated.cs so that when i create my partial classes for the Entities i can use the name <EntityName> for my class files.

Rkaufman · Accepted Answer · 2013-11-22 12:49:13Z

1

You can modify the Entities.tt file. More specifically modify the "AccessibilityAndVirtual" method to handle your specific situation. As this template is specific to your current project you do not have to worry about reuse in other projects. You should be able to selectively define which property names you want to exclude from lazy loading. Happy coding.

answered Nov 22, 2013 at 12:49

Rkaufman

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Comments

Joakim · Accepted Answer · 2013-06-08 16:16:27Z

0

if I understand you correctly what you want is .Include("Requestor")

Person person =
        context.Persons.Include("Requestor").FirstOrDefault();

this would get a Person and the Requestor in one trip to the db for that query.

Edit: Looking a bit more, this was assuming you had the Property of Requestor on the Person entity, you can however just change this to the appropriate entity and property.

answered Jun 8, 2013 at 16:16

Joakim

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1 Comment

Sportball Over a year ago

I understand why you might think what I'd want is eager loading of Requestor. But what I am interested in is learning selective disabling of lazy loading, which isn't the same thing (though very confusing at first to differentiate). I do also have a question (in my head as of now) as to how modify the model or templates to selectively have eager loading with a Database First technique.

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