How to check if the file already exists in the LinkItemCollection? - episerver-7

Question

I'm using EPiServer CMS 7.5. I have a block that has a LinkItemCollection property.
public virtual LinkItemCollection LinkList { get; set; }
The user can drag-and-drop any document from the Assets pane into the Link Item Collection. How do I prevent the user from adding a document that already exists in the Link Item Collection?

Answer 1

Ok I have found a way to check duplicates in a Link Item Collection while in forms edit mode.
I have created a helper class that checks duplicates in a collection:
public static class EnumerableExtensions
{
public static bool HasDuplicates<T>(this IEnumerable<T> subjects)
{
return HasDuplicates(subjects, EqualityComparer<T>.Default);
}
public static bool HasDuplicates<T>(this IEnumerable<T> subjects, IEqualityComparer<T> comparer)
{
if (subjects == null)
throw new ArgumentNullException("subjects");
if (comparer == null)
throw new ArgumentNullException("comparer");
var set = new HashSet<T>(comparer);
foreach (var s in subjects)
if (!set.Add(s))
return true;
return false;
}
Then I created a custom Validator for my Link Item Collection:
public class LinkItemCollectionValidator : IValidate<LinkItemCollection>
{
public IEnumerable<ValidationError> Validate(LinkItemCollection instance)
{
var errors = new List<ValidationError>();
List<string> list = new List<string>();
foreach (var i in instance)
{
list.Add(i.Text);
}
if (list.HasDuplicates())
{
errors.Add(new ValidationError()
{
ErrorMessage = "Duplicate content is not allowed",
PropertyName = "LinkList",
Severity = ValidationErrorSeverity.Error,
ValidationType = ValidationErrorType.StorageValidation
});
}
return errors;
}