KeyedCollection Error

Question

I'm fairly new to C# collectons. I do not know how to solve this issue.

This line of code

public class clsFeatureCollection : KeyedCollection<string, clsFeature>

Gives the error

'clsFeatureCollection' does not implement inherited abstract member 'System.Collections.ObjectModel.KeyedCollection<string, clsFeature>.GetKeyForItem(clsFeature)'

This is the code I have. I am not sure how to correct this Can anyone help?

public class clsFeature
{
    private int m_OID { get; set; }
    private IGeometry m_Geometry { get; set; }
}

public class clsFeatureCollection : KeyedCollection<string, clsFeature> // : IEnumerable
{
    // ************************** Keyed Collection ****************
    // https://msdn.microsoft.com/en-us/library/ms132438(v=vs.100)

    public KeyedCollection<string, clsFeature> m_oCol; // KeyedCollection<string, clsFeature>();
    public Dictionary<string, string> m_oColReverse;

    public clsFeatureCollection() : base() 
    {
        m_oCol = new clsFeatureCollection();
        m_oColReverse = new Dictionary<string, string>();
    }

    public int GeyKeyForItem(clsFeature item)
    {
        return item.OID;
    }
}

Answer 1

Thanks everyone for their input and help

Below is the final working solution I came up with. It integrates with the other similar collections. I initially used a list but I needed a string as a key for the other collections

// ************************** Ordered Dictionary - works ****************
// http://stackoverflow.com/questions/2722767/c-sharp-order-preserving-data-structures
// http://www.go4expert.com/articles/understanding-c-sharp-dictionaries-t30034/

    public OrderedDictionary m_oCol;
    public OrderedDictionary m_oColReverse;

    public clsFeatureCollection()
        : base()
    {
        m_oCol = new OrderedDictionary();
        m_oColReverse = new OrderedDictionary();
    }

    public IEnumerator GetEnumerator()
    {
        return m_oCol.GetEnumerator();
    }

    public void Add(IFeature pFeature, string strBefore = "", string strAfter = "", bool bReverse = false)
    {
        if (bReverse == true)
        {
            m_oColReverse.Add(pFeature.OID.ToString().Trim(), pFeature.OID.ToString().Trim());
        }

        if (!ContainsItem(pFeature.OID.ToString()))
        {
            m_oCol.Add(pFeature.OID.ToString(), new clsFeature(pFeature.OID, pFeature.ShapeCopy));
        }
    }

    public void AddBefore(IFeature pFeature, string strBefore, bool bReverse = false)
    {
        if (bReverse == true)
        {
            m_oColReverse.Add(pFeature.OID.ToString().Trim(), pFeature.OID.ToString().Trim());
        }

        if (!ContainsItem(pFeature.OID.ToString()))
        {
            if (strBefore != null)
            {
                int index = GetIndex(m_oCol, strBefore);

                if (index > 0)
                {
                    m_oCol.Insert(index - 1, pFeature.OID.ToString(), new clsFeature(pFeature.OID, pFeature.ShapeCopy));

                }
                else
                {
                    m_oCol.Insert(0, pFeature.OID.ToString(), new clsFeature(pFeature.OID, pFeature.ShapeCopy));
                }
            }
        }
    }

    public void AddAfter(IFeature pFeature, string strAfter, bool bReverse = false)
    {
        if (bReverse == true)
        {
            m_oColReverse.Add(pFeature.OID.ToString().Trim(), pFeature.OID.ToString().Trim());
        }

        if (!ContainsItem(pFeature.OID.ToString()))
        {
            if (!string.IsNullOrEmpty(strAfter))
            {
                int index = GetIndex(m_oCol, strAfter);

                m_oCol.Insert(index + 1, pFeature.OID.ToString(), new clsFeature(pFeature.OID, pFeature.ShapeCopy));
            }
            else
            {
                m_oCol.Insert(0, pFeature.OID.ToString(), new clsFeature(pFeature.OID, pFeature.ShapeCopy));
            }
        }
    }

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

    public void Remove(int Id)
    {
        m_oCol.RemoveAt(Id);
    }

    public clsFeature Item(int Position)
    {
        try
        {
            clsFeature value = (clsFeature)m_oCol.Cast<DictionaryEntry>().ElementAt(Position).Value;

            return value;
        }
        catch (Exception)
        {
            throw;
        }
    }

    public void Clear()
    {
        m_oCol = new OrderedDictionary();
        m_oColReverse = new OrderedDictionary();
    }

    public bool Reverse(string valueRenamed)
    {
        bool bReverse = false;

        try
        {
            if (m_oColReverse.Contains(valueRenamed))
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        catch (Exception ex)
        {
            if (ex is ArgumentException | ex is IndexOutOfRangeException)
            {
                bReverse = false;
            }
        }

        return bReverse;
    }

    public bool ContainsItem(string oidValue)
    {
        bool bContainsItem = false;

        string intOID = oidValue.ToString();

        try
        {
            // dictionary
            if (m_oCol.Contains(intOID))
            {
                bContainsItem = true;
            }
            else
            {
                bContainsItem = false;
            }

            return bContainsItem;
        }

        catch (Exception ex)
        {
            if (ex is ArgumentException | ex is IndexOutOfRangeException)
            {
                bContainsItem = false;
            }
        }

        return bContainsItem;
    }

    public static int GetIndex(OrderedDictionary dictionary, string key)
    {
        for (int index = 0; index < dictionary.Count; index++)
        {
            if (dictionary[index] == dictionary[key])
            {
                return index;
            }
        }

        return -1;
    }
}

// ******************************  End Ordered Dictionary - works *****************************   

Answer 2

There's three major issues:

1. As in the other answer, there's a misspelling of the method name
2. KeyedCollection<TKey, TItem>.GetKeyForItem is supposed to return an object of type TKey (docs)
3. The line m_oCol = new clsFeatureCollection(); in the constructor recursively calls the constructor. Since KeyedCollection is abstract, you can't directly instantiate it. You need to call the base constructor with base(). (See this answer or this answer)