ICollection<T> Issue

I have a class that have two properties

public class FormField
{
public string FormCode { get; set; }
public string FieldCode { get; set; }
}

I have an another class that implements ICollection

public class FormFieldCollection : ICollection<FormField>
{
ICollection<FormField> m_form_field;

public FormFieldCollection()
{
m_form_field = new Collection<FormField>();
}

public void Add(FormField item)
{
m_form_field.Add(item);
}
public void Clear()
{
m_form_field.Clear();
}

public bool Contains(FormField item)
{
return m_form_field.Contains(item);
}

public void CopyTo(FormField[] array, int arrayIndex)
{
m_form_field.CopyTo(array, arrayIndex);
}

public int Count
{
get { return m_form_field.Count; }
}

public bool IsReadOnly
{
get { return m_form_field.IsReadOnly; }
}

public bool Remove(FormField item)
{
return m_form_field.Remove(item);
}

public IEnumerator<FormField> GetEnumerator()
{
return m_form_field.GetEnumerator();
}

IEnumerator IEnumerable.GetEnumerator()
{
return m_form_field.GetEnumerator();
}
}

I have a method in an another class that is returning ICollection interface

public class FormFieldXmlTesting
{
string filePath = @"C:\RnD\CollectionRnD\FormFieldXml.xml";

public ICollection RetriveAllUsingGenerics() where T : class
{
ICollection<FormField> projectCollection;
XDocument document = XDocument.Load(filePath);

projectCollection = (from XElement element in document.Elements("FormFields")
.Elements("Module").Elements("Field")
select new FormField{
FormCode = element.Parent.Attribute("Name").Value,
FieldCode = element.Attribute("Name").Value,
}).ToList();
return projectCollection as ICollection;
}
}

When I am calling the above method the output is astonizing me

FormFieldXmlTesting testing = new FormFieldXmlTesting();

//Returns correct output
ICollection<FormField> coll = testing.RetriveAllUsingGenerics<FormField>();

//Returns null values
FormFieldCollection collection = testing.RetriveAllUsingGenerics<FormField>() as FormFieldCollection;

Console.WriteLine(string.Format("ICollection record fetched: {0}", coll == null ? 0 : coll.Count));
Console.WriteLine(string.Format("FormFieldCollection record fetched: {0}", collection == null ? 0 : collection.Count));
Console.ReadLine();

The xml used in the application is as follows

1 Reply

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Vulpes15y ago
The problem is that the ICollection returned by testing.RetriveAllUsingGenerics() is really a List and not a FormFieldCollection object.

I'd see if this works instead:

List list = testing.RetriveAllUsingGenerics() as List;

FormFieldCollection collection = new FormFieldCollection();
foreach(FormField ff in list) collection.Add(ff);