Business Rules

[Luka803]

Hello community!

I have created custom async business rule which should check if the account with the same name already exists which work just fine, it triggers and return proper result.

private class NameAlreadyExist : BusinessRuleAsync
{
    private IUnitOfWork UnitOfWork { get; set; }

    public NameAlreadyExist(IUnitOfWork unitOfWork, IPropertyInfo property) : base(property)
    {
        UnitOfWork = unitOfWork;
        IsAsync = true;
        ProvideTargetWhenAsync = true;
    }
    protected override async Task ExecuteAsync(IRuleContext context)
    {
        var target = (AccountEdit)context.Target;
        var input = (string)ReadProperty(target, NameProperty);
        var result = await UnitOfWork.Account.NameAlreadyExist(input);
        if (result)
            context.AddErrorResult($"Account with this name: {input} already exist");
    }

}

The problem is that my BrokenRulesCollection is null so i cant display message from this particular rule. For example, my DataAnnotation rule displays just fine but those custom rules are not provided in BrokenRulesCollection. I ll also provide other code for rules:

1. Calling rule
   this.BusinessRules.AddRule(new NameAlreadyExist(service, NameProperty));
2. Input field at UI where i mapped NameProperty

<div>
    <label>@Property.FriendlyName</label>
    <input @bind-value="@TextValue" @bind-value:event="oninput" />
    <span class="text-danger">@Property.ErrorText</span>
    <span>Is busy: @Property.IsBusy</span>
</div>

@code {
#nullable disable
    [Parameter]
    public Csla.Blazor.IPropertyInfo Property { get; set; }

    private string TextValue
    {
        get => (string)Property.Value;
        set => Property.Value = value;
    }
}

Thanks in advance!

[ajohnstone-ks]

I'm not sure why BRC would be null, but I would ask why you're using the Target and not context.GetInputProperty. Also your UOW can't be injected like that; you'll need to use context.ApplicationContext.GetRequiredService<IUnitOfWork>()

Is your business rule add code in an override for AddBusinessRules

[Luka803]

Hey @ajohnstone-ks, thanks for response.

For first question, i was looking at ProjectTracker project from Git examples and there are few custom rules that are defined like i did.
I injected UOW at AddBusinessRules method and then passed that into rule constructor:

protected override void AddBusinessRules()
{
    var service = ApplicationContext.GetRequiredService<IUnitOfWork>();
    base.AddBusinessRules();
    this.BusinessRules.AddRule(new NameAlreadyExist(service)
    {
        PrimaryProperty = NameProperty
    });

}

I set breakpoint at UI Save method and BrokenRulesColletion of vm.Model is null, which is the whole problem... If you have any ideas, feel free to type.
Thanks!

[Luka803]

If someone would have same problem, it cannot go like i did with UOW. You must go via IDataPortal of the object which will return list of the objects from the database or it's just my soultion.

 private class NameAlreadyExist : BusinessRuleAsync
 {
     public NameAlreadyExist(IPropertyInfo property) : base(property)
     {
         ProvideTargetWhenAsync = true;
         IsAsync = true;
         InputProperties = new List<IPropertyInfo> { PrimaryProperty };
     }
     protected override async Task ExecuteAsync(IRuleContext context)
     {
         var service = context.ApplicationContext.GetRequiredService<IDataPortal<AccountList>>();
         string input = (string)context.InputPropertyValues[PrimaryProperty];
         var result = await service.FetchAsync();
         foreach (var item in result)
         {
             if (item.Name == input)
             {
                 context.AddErrorResult($"Account with this input {input} already exist");
                 break;
             }
         }
     }
 }

Now, it work just fine.

[StefanOssendorf]

I'm glad you solved your problem.
One thought though: If your AccountList is growing over time, you are loading the whole list potentially lot of times onto the client just to check if the name is already in use. My suggestion here is to use a dedicated command which something like NameAlreadyExistCommand which uses the Name as a parameter and returns a bool. This saves imho a lot of traffic between client and server.

[Luka803]

Hey @StefanOssendorf thank you for the suggestion. I am aware of that, but i am a beginer in term of CSLA, so i still catch up things and the concepts of the framework. This is just example i am practicing on , not a real application 😄. I will consider your solution!

Thanks!