If you read my blog backward you will find some implementations of IDataErrorInfo. I’ve even implemented IDataErrorInfo with AOP in unhaddins. I found the interface useful when I want to show validations errors through a DataBinding infrastructure, WPF, WinForms or even Asp.Net MVC.
In my last post, there are some comments about service locator:
- Mauricio Scheffer said; “It's just easier and more maintainable to use real dependency injection.”
- Ivan Korneliuk said; “I prefer to inject IServiceLocator abstraction for such classes, rather than using global ServiceLocator.”
And I agree with both, but there are corner cases.
So, this is all I need to implement IDataErrorInfo in my base entity:
public class BaseEntity : ComparableEntity, IDataErrorInfo
{
private static IEntityValidator entityValidator;
private static IEntityValidator EntityValidator
{
get
{
if (entityValidator == null)
{
return entityValidator
= ServiceLocator
.Current
.GetInstance<IEntityValidator>();
}
return entityValidator;
}
}
string IDataErrorInfo.this[string columnName]
{
get
{
var errors = EntityValidator
.Validate(this, columnName)
.Select(iv => iv.Message)
.ToArray();
return string.Join(Environment.NewLine, errors);
}
}
string IDataErrorInfo.Error
{
get
{
var errors = EntityValidator
.Validate(this)
.Select(iv => iv.Message)
.ToArray();
return string.Join(Environment.NewLine, errors);
}
}
}
Yes, there are some posts about dependency injection in entities, and I’ve done months ago, but it is over complicated for this case. So, with this code, I am not injecting IServiceLocator, and I am not injecting IValidatorEngine. I’m just using a good pattern :)
You can test this code with the code in my previous post.
