DevForce 2010: Navigation Property Verification

Navigation Property Verification

Printed From: IdeaBlade
Category: DevForce
Forum Name: DevForce 2010
Forum Discription: For .NET 4.0
URL: http://www.ideablade.com/forum/forum_posts.asp?TID=2540
Printed Date: 29-Jul-2026 at 4:58pm

Topic: Navigation Property Verification

Posted By: smi-mark
Subject: Navigation Property Verification
Date Posted: 02-Mar-2011 at 5:09pm

Is there an inbuilt way for making sure navigation properties are not null? I've done this, but i wondered if there was perhaps a better way.

public class NullEntityVerifier : PropertyValueVerifier
    {
        public NullEntityVerifier(Type entityType, String propertyName,
          String displayName = null, bool? shouldTreatEmptyStringAsNull = null)
            : base(new PropertyValueVerifierArgs(entityType, propertyName, false,
              displayName, shouldTreatEmptyStringAsNull))
        {
        }

        protected override VerifierResult VerifyValue(object itemToVerify, object valueToVerify, TriggerContext triggerContext, VerifierContext verifierContext)
        {
            var entity = (Entity)valueToVerify;
            var result = !entity.EntityAspect.IsNullEntity;
            return new VerifierResult(result);
        }

    }

Then I added this into my provider. I attempted to use the buddy class method to add the verifier but it didn't seem to work, so at this moment in time I have it in my VerifierProvider.

Replies:

Posted By: DenisK
Date Posted: 04-Mar-2011 at 10:50am

Hi smi-mark;

We don't have an in-built way of doing this. So your verifier solution seems to be perfectly reasonable.

Let me check on the buddy class method and get back to you.

Posted By: DenisK
Date Posted: 07-Mar-2011 at 12:29pm

Hi smi-mark;

I've tested the buddy class method of adding the verifier and it seems to work for me. Perhaps I misunderstood something specific to your use case?

Here's my test.

//The NullEntityVerifier

public class NullEntityVerifier : PropertyValueVerifier {

public NullEntityVerifier(Type entityType, String propertyName,

String displayName = null, bool? shouldTreatEmptyStringAsNull = null)

: base(new PropertyValueVerifierArgs(entityType, propertyName, false,

displayName, shouldTreatEmptyStringAsNull)) {

}

public NullEntityVerifier(PropertyValueVerifierArgs args) : base(args) { }

protected override VerifierResult VerifyValue(object itemToVerify, object valueToVerify,

TriggerContext triggerContext, VerifierContext verifierContext) {

var entity = (Entity)valueToVerify;

var result = !entity.EntityAspect.IsNullEntity;

return new VerifierResult(result);

}

//The NullEntityVerifierAttribute

[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field, Inherited = false)]

public class NullEntityVerifierAttribute : PropertyValueVerifierAttribute {

protected override Verifier BuildVerifierCore(Type pType, String propertyName) {

return new NullEntityVerifier(

new PropertyValueVerifierArgs(pType, propertyName, false, DisplayName,

GetShouldTreatEmptyStringAsNull())

);

}

//The buddy class

public class EmployeeMetadata {

[NullEntityVerifier]

public static Employee Manager;

}

//The generated code

#region Manager property

/// <summary>Gets or sets the Manager. </summary>

[DomainModel.Employee.NullEntityVerifier]

[Bindable(false)]

[Display(Name="Manager", AutoGenerateField=false)]

[DataMember]

[IbEm.RelationProperty("FK_Employee_Employee", IbEm.QueryDirection.ToRole2)]

public Employee Manager {

get { return PropertyMetadata.Manager.GetValue(this); }

set { PropertyMetadata.Manager.SetValue(this, value); }

}

#endregion Manager property

Posted By: smi-mark
Date Posted: 07-Mar-2011 at 9:35pm

Hi Denis,

I think I tested it with the RequiredValueVerifier at first, and since it didn't generate anything for the navigation property, I assumed it didn't work. I'll try it with my null verifier tomorrow.

Thanks for looking into it.

Posted By: DenisK
Date Posted: 08-Mar-2011 at 11:18am

Hi smi-mark;

I just tested it with the RequiredValueVerifier. And although code generation picked it up, it won't work with navigational property since RequiredValueVerifier deals with null values and a "null" navigational property is not exactly null but rather a "detached/null entity".