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Custom BindableDictionary binded to BindingSource not refreshing Inner List object

Problem:
I'm trying to bind a Dictionary<string key, string value> to BindingSource and use it as DataSource for a ListBox control in a form but it did not work. Later I found that Dictionary does not implement INotifyPropertyChanged interface which is necessary for the BindingSource to work properly.
Any similar topic posted before this wasn't of much help and did not work for me.
Tried Solution:
To cope with the BindingSource's constraint I tried writing a custom dictionary class BindableDictionary with necessary interface implemented. The final layout of my custom dictionary class is:
public class BindableDictionary<TKey, TValue> : IDictionary<TKey, TValue>, INotifyPropertyChanged
{
private readonly IDictionary<TKey, TValue> dictionary;
public BindableDictionary() : this(new Dictionary<TKey, TValue>()) { }
public BindableDictionary(IDictionary<TKey, TValue> dict)
{
dictionary = dict;
}
public TValue this[TKey key] { get => dictionary[key]; set => ReflectChange(key, value); }
public int Count => dictionary.Count;
public bool IsReadOnly => dictionary.IsReadOnly;
public ICollection<TKey> Keys => dictionary.Keys;
public ICollection<TValue> Values => dictionary.Values;
protected virtual event PropertyChangedEventHandler PropertyChanged;
event PropertyChangedEventHandler INotifyPropertyChanged.PropertyChanged
{
add
{
PropertyChanged += value;
}
remove
{
PropertyChanged -= value;
}
}
protected virtual void OnPropertyChanged(string property)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(property));
}
public void Add(KeyValuePair<TKey, TValue> item) => Add(item.Key, item.Value);
public void Add(TKey key, TValue value) => ReflectAdd(key, value);
public void Clear()
{
dictionary.Clear();
OnPropertyChanged("Count");
OnPropertyChanged("Keys");
OnPropertyChanged("Values");
}
public bool Contains(KeyValuePair<TKey, TValue> item) => dictionary.Contains(item);
public bool ContainsKey(TKey key) => dictionary.ContainsKey(key);
public void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex) => dictionary.CopyTo(array, arrayIndex);
public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator() => dictionary.GetEnumerator();
public bool Remove(KeyValuePair<TKey, TValue> item) => ReflectRemove(item.Key);
private bool ReflectRemove(TKey key)
{
if (dictionary.TryGetValue(key, out TValue value) && dictionary.Remove(key))
{
OnPropertyChanged("Count");
OnPropertyChanged("Keys");
OnPropertyChanged("Values");
OnPropertyChanged("Item[]");
return true;
}
return false;
}
private void ReflectAdd(TKey key, TValue value)
{
dictionary.Add(key, value);
OnPropertyChanged("Count");
OnPropertyChanged("Keys");
OnPropertyChanged("Values");
OnPropertyChanged("Item[]");
}
private void ReflectChange(TKey key, TValue value)
{
if (dictionary.TryGetValue(key, out TValue oldValue))
{
dictionary[key] = value;
OnPropertyChanged("Values");
OnPropertyChanged("Item[]");
}
else
{
ReflectAdd(key, value);
}
}
public bool Remove(TKey key) => ReflectRemove(key);
public bool TryGetValue(TKey key, out TValue value) => dictionary.TryGetValue(key, out value);
IEnumerator IEnumerable.GetEnumerator() => dictionary.GetEnumerator();
}
public partial class Form1 : Form
{
BindableDictionary<string, string> AttachDictionary = new BindableDictionary<string, string>();
BindingSource AttachSource;
public Form1()
{
InitializeComponent();
listBox1.DisplayMember = "Key";
listBox1.ValueMember = "Value";
listBox1.DataSource = AttachSource = new BindingSource(AttachDictionary, null);
}
private void button1_Click(object sender, EventArgs e)
{
using (OpenFileDialog OFD = new OpenFileDialog())
{
if (OFD.ShowDialog() == DialogResult.OK)
{
AttachDictionary.Add(OFD.SafeFileName, OFD.FileName);
AttachSource.ResetBindings(false);
}
}
}
}
Conclusion:
Even though I implemented the interface, I found that the inner List object of BindingSource is not being refreshed despite the DataSource getting updated and the list box do not refreshes with new items added.
One alternate Solution by using an ObservableCollection works successfully with BindingSource which I don't know why in my limited knowledge. I tried inspecting the source of ObservableCollection and BindingSource but it was too vast to process at once.
My thought process says that the change in DataSource is not reflecting properly and hence the BindingSource does not realize any update. There could be problem with event hooking maybe?

Generic implementation of OrderDictionary in C# is showing ambiguous method warnings

Since C# has no generic implementation of the OrderedDictionary at the time of asking this question I downloaded one from here. To be very clear I am using this in the Unity game engine with MonoDevelop to code a game.
The implementation seems nicely put together however it gives me an ambiguous method call warning the solution to which I can't seem to figure out. Can somebody please explain me what is going on here and propose a possible solution to get rid of the warnings?
To be specific here are the similar method calls:
IDictionaryEnumerator IOrderedDictionary.GetEnumerator()
{
return Dictionary.GetEnumerator();
}
IDictionaryEnumerator IDictionary.GetEnumerator()
{
return Dictionary.GetEnumerator();
}
IEnumerator IEnumerable.GetEnumerator()
{
return List.GetEnumerator();
}
IEnumerator<KeyValuePair<TKey, TValue>> IEnumerable<KeyValuePair<TKey,TValue>>.GetEnumerator()
{
return List.GetEnumerator();
}
And here is the error:
[Warning] [CS0278] `TurboLabz.Game.IOrderedDictionary<string,TurboLabz.Game.RoomInfo>' contains ambiguous implementation of `enumerable' pattern.
Method `System.Collections.Specialized.IOrderedDictionary.GetEnumerator()' is ambiguous with method `System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string,TurboLabz.Game.RoomInfo>>.GetEnumerator()'
Thanks in advance.
Edit:
Here is the source and its usage in the codebase that I have:
IOrderedDictionary.cs
using System.Collections.Generic;
using System.Collections.Specialized;
namespace TurboLabz.Game
{
public interface IOrderedDictionary<TKey, TValue> : IOrderedDictionary, IDictionary<TKey, TValue>
{
new int Add(TKey key, TValue value);
void Insert(int index, TKey key, TValue value);
new TValue this[int index]
{
get;
set;
}
}
}
OrderedDictionary.cs
using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
namespace TurboLabz.Game
{
public class OrderedDictionary<TKey, TValue> : IOrderedDictionary<TKey, TValue>
{
private const int DefaultInitialCapacity = 0;
private static readonly string _keyTypeName = typeof(TKey).FullName;
private static readonly string _valueTypeName = typeof(TValue).FullName;
private static readonly bool _valueTypeIsReferenceType = !typeof(ValueType).IsAssignableFrom(typeof(TValue));
private Dictionary<TKey, TValue> _dictionary;
private List<KeyValuePair<TKey, TValue>> _list;
private IEqualityComparer<TKey> _comparer;
private object _syncRoot;
private int _initialCapacity;
public OrderedDictionary()
: this(DefaultInitialCapacity, null)
{
}
public OrderedDictionary(int capacity)
: this(capacity, null)
{
}
public OrderedDictionary(IEqualityComparer<TKey> comparer)
: this(DefaultInitialCapacity, comparer)
{
}
public OrderedDictionary(int capacity, IEqualityComparer<TKey> comparer)
{
if(0 > capacity)
throw new ArgumentOutOfRangeException("capacity", "'capacity' must be non-negative");
_initialCapacity = capacity;
_comparer = comparer;
}
private static TKey ConvertToKeyType(object keyObject)
{
if(null == keyObject)
{
throw new ArgumentNullException("key");
}
else
{
if(keyObject is TKey)
return (TKey)keyObject;
}
throw new ArgumentException("'key' must be of type " + _keyTypeName, "key");
}
private static TValue ConvertToValueType(object value)
{
if(null == value)
{
if(_valueTypeIsReferenceType)
return default(TValue);
else
throw new ArgumentNullException("value");
}
else
{
if(value is TValue)
return (TValue)value;
}
throw new ArgumentException("'value' must be of type " + _valueTypeName, "value");
}
private Dictionary<TKey, TValue> Dictionary
{
get
{
if(null == _dictionary)
{
_dictionary = new Dictionary<TKey, TValue>(_initialCapacity, _comparer);
}
return _dictionary;
}
}
private List<KeyValuePair<TKey, TValue>> List
{
get
{
if(null == _list)
{
_list = new List<KeyValuePair<TKey, TValue>>(_initialCapacity);
}
return _list;
}
}
IDictionaryEnumerator IOrderedDictionary.GetEnumerator()
{
return Dictionary.GetEnumerator();
}
IDictionaryEnumerator IDictionary.GetEnumerator()
{
return Dictionary.GetEnumerator();
}
IEnumerator IEnumerable.GetEnumerator()
{
return List.GetEnumerator();
}
IEnumerator<KeyValuePair<TKey, TValue>> IEnumerable<KeyValuePair<TKey,TValue>>.GetEnumerator()
{
return List.GetEnumerator();
}
public void Insert(int index, TKey key, TValue value)
{
if(index > Count || index < 0)
throw new ArgumentOutOfRangeException("index");
Dictionary.Add(key, value);
List.Insert(index, new KeyValuePair<TKey, TValue>(key, value));
}
void IOrderedDictionary.Insert(int index, object key, object value)
{
Insert(index, ConvertToKeyType(key), ConvertToValueType(value));
}
public void RemoveAt(int index)
{
if(index >= Count || index < 0)
throw new ArgumentOutOfRangeException("index", "'index' must be non-negative and less than the size of the collection");
TKey key = List[index].Key;
List.RemoveAt(index);
Dictionary.Remove(key);
}
public TValue this[int index]
{
get
{
return List[index].Value;
}
set
{
if(index >= Count || index < 0)
throw new ArgumentOutOfRangeException("index", "'index' must be non-negative and less than the size of the collection");
TKey key = List[index].Key;
List[index] = new KeyValuePair<TKey, TValue>(key, value);
Dictionary[key] = value;
}
}
object IOrderedDictionary.this[int index]
{
get
{
return this[index];
}
set
{
this[index] = ConvertToValueType(value);
}
}
void IDictionary<TKey, TValue>.Add(TKey key, TValue value)
{
Add(key, value);
}
public int Add(TKey key, TValue value)
{
Dictionary.Add(key, value);
List.Add(new KeyValuePair<TKey,TValue>(key, value));
return Count - 1;
}
void IDictionary.Add(object key, object value)
{
Add(ConvertToKeyType(key), ConvertToValueType(value));
}
public void Clear()
{
Dictionary.Clear();
List.Clear();
}
public bool ContainsKey(TKey key)
{
return Dictionary.ContainsKey(key);
}
bool IDictionary.Contains(object key)
{
return ContainsKey(ConvertToKeyType(key));
}
bool IDictionary.IsFixedSize
{
get
{
return false;
}
}
public bool IsReadOnly
{
get
{
return false;
}
}
ICollection IDictionary.Keys
{
get
{
return (ICollection)Keys;
}
}
public int IndexOfKey(TKey key)
{
if(null == key)
throw new ArgumentNullException("key");
for(int index = 0; index < List.Count; index++)
{
KeyValuePair<TKey, TValue> entry = List[index];
TKey next = entry.Key;
if(null != _comparer)
{
if(_comparer.Equals(next, key))
{
return index;
}
}
else if(next.Equals(key))
{
return index;
}
}
return -1;
}
public bool Remove(TKey key)
{
if(null == key)
throw new ArgumentNullException("key");
int index = IndexOfKey(key);
if(index >= 0)
{
if(Dictionary.Remove(key))
{
List.RemoveAt(index);
return true;
}
}
return false;
}
void IDictionary.Remove(object key)
{
Remove(ConvertToKeyType(key));
}
ICollection IDictionary.Values
{
get
{
return (ICollection)Values;
}
}
public TValue this[TKey key]
{
get
{
return Dictionary[key];
}
set
{
if(Dictionary.ContainsKey(key))
{
Dictionary[key] = value;
List[IndexOfKey(key)] = new KeyValuePair<TKey, TValue>(key, value);
}
else
{
Add(key, value);
}
}
}
object IDictionary.this[object key]
{
get
{
return this[ConvertToKeyType(key)];
}
set
{
this[ConvertToKeyType(key)] = ConvertToValueType(value);
}
}
void ICollection.CopyTo(Array array, int index)
{
((ICollection)List).CopyTo(array, index);
}
public int Count
{
get
{
return List.Count;
}
}
bool ICollection.IsSynchronized
{
get
{
return false;
}
}
object ICollection.SyncRoot
{
get
{
if(this._syncRoot == null)
{
System.Threading.Interlocked.CompareExchange(ref this._syncRoot, new object(), null);
}
return this._syncRoot;
}
}
public ICollection<TKey> Keys
{
get
{
return Dictionary.Keys;
}
}
public bool TryGetValue(TKey key, out TValue value)
{
return Dictionary.TryGetValue(key, out value);
}
public ICollection<TValue> Values
{
get
{
return Dictionary.Values;
}
}
void ICollection<KeyValuePair<TKey,TValue>>.Add(KeyValuePair<TKey, TValue> item)
{
Add(item.Key, item.Value);
}
bool ICollection<KeyValuePair<TKey,TValue>>.Contains(KeyValuePair<TKey, TValue> item)
{
return ((ICollection<KeyValuePair<TKey,TValue>>)Dictionary).Contains(item);
}
void ICollection<KeyValuePair<TKey,TValue>>.CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
{
((ICollection<KeyValuePair<TKey,TValue>>)Dictionary).CopyTo(array, arrayIndex);
}
bool ICollection<KeyValuePair<TKey,TValue>>.Remove(KeyValuePair<TKey, TValue> item)
{
return Remove(item.Key);
}
}
}
This is how the above given OrderedDictionary is being used:
IRoomSettingsModel.cs
namespace TurboLabz.Game
{
public interface IRoomSettingsModel
{
IOrderedDictionary<string, RoomInfo> settings { get; set; }
}
}
RoomSettingsModel.cs
namespace TurboLabz.Game
{
public class RoomSettingsModel : IRoomSettingsModel
{
public IOrderedDictionary<string, RoomInfo> settings { get; set; }
public RoomSettingsModel()
{
settings = new OrderedDictionary<string, RoomInfo>();
}
}
public struct RoomInfo
{
public string id;
public long gameDuration;
public long prize;
}
}
GSService.cs
namespace TurboLabz.Game
{
public class SomeService
{
public IRoomSettingsModel roomSettingsModel = new RoomSettingsModel();
public void ReadModel()
{
foreach (KeyValuePair<string, RoomInfo> room in roomSettingsModel.settings)
{
RoomInfo roomInfo = room.Value;
Debug.Log(roomInfo.id);
}
}
}
}
To keep things confidential I've changed the code a bit here but overall it should deliver the idea. The most important statement in usage above is foreach (KeyValuePair<string, RoomInfo> room in roomSettingsModel.settings) which is the source of the warning. It's in this line that I think the compiler gets confused about which GetEnumerator() method to call.
Firstly, is that really the issue? Secondly, how do I resolve the problem?

I tried to follow what you've done, but it's a spaghetti of nested interfaces.
If you put breakpoints in every GetEnumerator() in OrderedDictionary, you may find it is not calling the enumerator you expect.
The problem, I think, is with trying to implement the non-generic IOrderedDictionary interface along with IDictionary<TKey, TValue>.
If you want generics, why do you need to maintain compatibilty with non-generic IOrderedDictionary?
If you follow (F12) the inheritance trail of IOrderedDictionary, it inherits IDictionary, ICollection, IEnumerable.
Then IDictionary<TKey, TValue> inherits from ICollection<KeyValuePair<TKey, TValue>>, IEnumerable<KeyValuePair<TKey, TValue>>, IEnumerable.
I'm not quite sure what all your requirements are, but I would drop any interfaces you don't need to support. Don't provide code features that you don't need.
This is not completely of your making, but it is the consequence of trying to support multiple interfaces with lots of baggage of their own.
Based on your question, I would only support IDictionary<TKey, TValue> & IList<T>.
And their baggage ;)
For those curious about KeyedCollection, here's an implmentation that does most of what #Mubeen implemented in his code. This is not fully tested, so don't just do a copy->paste if you use this.
using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Collections.ObjectModel;
namespace TurboLabz.Game
{
public class GenericComparer<TKey> : IComparer<TKey>
{
public static GenericComparer<TKey> CreateComparer(Func<TKey, TKey, int> comparer)
{
return new GenericComparer<TKey>(comparer);
}
internal GenericComparer(Func<TKey, TKey, int> comparer)
{
Comparer = comparer;
}
private Func<TKey, TKey, int> Comparer { get; set; }
public int Compare(TKey x, TKey y)
{
return Comparer(x, y);
}
}
public class OrderedDictionaryKC<TKey, TValue> : KeyedCollection<TKey,KeyValuePair<TKey, TValue>>
{
public OrderedDictionaryKC()
{ }
public OrderedDictionaryKC(IEnumerable<KeyValuePair<TKey, TValue>> collection)
{
if (collection != null)
{
foreach (KeyValuePair<TKey, TValue> item in collection)
{
base.Add(item);
}
}
}
public OrderedDictionaryKC(IDictionary<TKey, TValue> dictionary) : this((IEnumerable<KeyValuePair<TKey, TValue>>)dictionary)
{ }
public ICollection<TKey> Keys
{
get
{
return base.Dictionary.Keys;
}
}
public ICollection<KeyValuePair<TKey, TValue>> Values
{
get
{
return base.Dictionary.Values;
}
}
public void Add(TKey key, TValue value)
{
if (key == null)
{
throw new ArgumentNullException("key");
}
base.Add(new KeyValuePair<TKey, TValue>(key, value));
}
public bool ContainsKey(TKey key)
{
if (key == null)
{
throw new ArgumentNullException("key");
}
return base.Dictionary.ContainsKey(key);
}
public bool TryGetValue(TKey key, out TValue value)
{
KeyValuePair<TKey, TValue> outValue;
var result= base.Dictionary.TryGetValue(key, out outValue);
value = outValue.Value;
return result;
}
protected override TKey GetKeyForItem(KeyValuePair<TKey, TValue> item)
{
return item.Key;
}
}
}

I ended up writing a new implementation which is a pure generic wrapper around System.Collections.Specialized.OrderedDictionary.
Although this is not an answer to the original question, it is warning free and, like #ashley-pillay mentioned in his answer, implements only the necessary interfaces.
I am providing the implementation here in hopes of helping others since it's hard to find a good implementation of a warning free generic OrderedDictionary even after a lot of Googling.
IOrderedDictionary.cs
using System.Collections.Generic;
namespace TurboLabz.Common
{
public interface IOrderedDictionary<TKey, TValue> :
IDictionary<TKey, TValue>,
ICollection<KeyValuePair<TKey, TValue>>,
IEnumerable<KeyValuePair<TKey, TValue>>
{
}
}
OrderedDictionary.cs
//-----------------------------------------------------------------------------
// Initial code provided by Microsoft Corporation. All rights reserved.
//-----------------------------------------------------------------------------
using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
namespace TurboLabz.Common
{
// System.Collections.Specialized.OrderedDictionary is NOT generic.
// This class is essentially a generic wrapper for OrderedDictionary.
public class OrderedDictionary<TKey, TValue> : IOrderedDictionary<TKey, TValue>
{
private OrderedDictionary _internalDictionary;
public OrderedDictionary()
{
_internalDictionary = new OrderedDictionary();
}
public OrderedDictionary(IDictionary<TKey, TValue> dictionary)
{
if (dictionary != null)
{
_internalDictionary = new OrderedDictionary();
foreach (KeyValuePair<TKey, TValue> pair in dictionary)
{
_internalDictionary.Add(pair.Key, pair.Value);
}
}
}
public int Count
{
get
{
return _internalDictionary.Count;
}
}
public bool IsReadOnly
{
get
{
return false;
}
}
public TValue this[TKey key]
{
get
{
if (key == null)
{
throw new ArgumentNullException("key");
}
if (_internalDictionary.Contains(key))
{
return (TValue)_internalDictionary[(object)key];
}
else
{
throw new KeyNotFoundException("Cannot find key " + key);
}
}
set
{
if (key == null)
{
throw new ArgumentNullException("key");
}
_internalDictionary[(object)key] = value;
}
}
public ICollection<TKey> Keys
{
get
{
IList<TKey> keys = new List<TKey>(_internalDictionary.Count);
foreach (TKey key in _internalDictionary.Keys)
{
keys.Add(key);
}
// Keys should be put in a ReadOnlyCollection,
// but since this is an internal class, for performance reasons,
// we choose to avoid creating yet another collection.
return keys;
}
}
public ICollection<TValue> Values
{
get
{
IList<TValue> values = new List<TValue>(_internalDictionary.Count);
foreach (TValue value in _internalDictionary.Values)
{
values.Add(value);
}
// Values should be put in a ReadOnlyCollection,
// but since this is an internal class, for performance reasons,
// we choose to avoid creating yet another collection.
return values;
}
}
public void Add(KeyValuePair<TKey, TValue> item)
{
Add(item.Key, item.Value);
}
public void Add(TKey key, TValue value)
{
if (key == null)
{
throw new ArgumentNullException("key");
}
_internalDictionary.Add(key, value);
}
public void Clear()
{
_internalDictionary.Clear();
}
public bool Contains(KeyValuePair<TKey, TValue> item)
{
if ((item.Key == null) || !(_internalDictionary.Contains(item.Key)))
{
return false;
}
else
{
return _internalDictionary[(object)item.Key].Equals(item.Value);
}
}
public bool ContainsKey(TKey key)
{
if (key == null)
{
throw new ArgumentNullException("key");
}
return _internalDictionary.Contains(key);
}
public void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
{
if (array == null)
{
throw new ArgumentNullException("array");
}
if (arrayIndex < 0)
{
throw new ArgumentOutOfRangeException("arrayIndex");
}
if ((array.Rank > 1) ||
(arrayIndex >= array.Length) ||
((array.Length - arrayIndex) < _internalDictionary.Count))
{
throw new Exception("Fx.Exception.Argument('array', SRCore.BadCopyToArray)");
}
int index = arrayIndex;
foreach (DictionaryEntry entry in _internalDictionary)
{
array[index] = new KeyValuePair<TKey, TValue>((TKey)entry.Key, (TValue)entry.Value);
++index;
}
}
public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
{
foreach (DictionaryEntry entry in _internalDictionary)
{
yield return new KeyValuePair<TKey, TValue>((TKey)entry.Key, (TValue)entry.Value);
}
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
public bool Remove(KeyValuePair<TKey, TValue> item)
{
if (Contains(item))
{
_internalDictionary.Remove(item.Key);
return true;
}
else
{
return false;
}
}
public bool Remove(TKey key)
{
if (key == null)
{
throw new ArgumentNullException("key");
}
if (_internalDictionary.Contains(key))
{
_internalDictionary.Remove(key);
return true;
}
else
{
return false;
}
}
public bool TryGetValue(TKey key, out TValue value)
{
if (key == null)
{
throw new ArgumentNullException("key");
}
bool keyExists = _internalDictionary.Contains(key);
value = keyExists ? (TValue)_internalDictionary[(object)key] : default(TValue);
return keyExists;
}
}
}

Add Element to Dictionary of Lists

I have
Dictionary<string, List<int>> myDict = new Dictionary<string, List<int>>();
and at some points I want to add numbers to myDict for a specific Dictionary key.
I am currently doing
if (!myDict.ContainsKey(newKey)){
myDict[newKey] = new List<int>();
}
myDict[newKey].Add(myNumber);
but that seems to be error prone to forgetting the ContainsKey check at some point.
I have searched for a way to make Dictionaries return a new List in case myDict["entry"] doesn't exist yet, but I couldn't find anything.

Here's a relatively simple implementation of the LazyLookup example I mentioned. It only implements IEnumerable out of brevity/simplicity to answer the question.
Essentially, upon accessing an index, it will make sure it has already been initialized to a new instance of the List<T> class.
public class LazyLookup<TKey, TValue> : IEnumerable<List<TValue>>
{
private readonly Dictionary<TKey, List<TValue>> CachedEntries;
private readonly Func<List<TValue>> LazyListCreator;
public LazyLookup()
: this(() => new List<TValue>())
{
}
public LazyLookup(Func<List<TValue>> lazyListCreator)
{
this.LazyListCreator = lazyListCreator;
this.CachedEntries = new Dictionary<TKey, List<TValue>>();
}
public List<TValue> this[TKey key]
{
get
{
return GetOrCreateValue(key);
}
}
private List<TValue> GetOrCreateValue(TKey key)
{
List<TValue> returnValue;
if (!CachedEntries.TryGetValue(key, out returnValue))
{
returnValue = LazyListCreator();
CachedEntries[key] = returnValue;
}
return returnValue;
}
public IEnumerator<List<TValue>> GetEnumerator()
{
return CachedEntries.Values.GetEnumerator();
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
}
With some usage:
var lazyLookup = new LazyLookup<string, int>();
lazyLookup["nocheck"].Add(9001);
//outputs 9001
Console.WriteLine(lazyLookup["nocheck"][0]);
//outputs 0 as it's a newly initialized list
Console.WriteLine(lazyLookup["someOtherLookup"].Count);
At this point, you could update it to be threadsafe (as GetOrCreateValue currently is not threadsafe), or generalize it so it doesn't assume it's of List<T> but any type, or extend it to implement the full IDictionary<TKey, TValue> interface. But at minimum, if the above pattern you posted is used often, you may consider swapping direct usage of the dictionaries with some encapsulation which trivializes the task for you and eliminates code duplication.

You can use TryGetValue:
List<int> list;
if(!myDict.TryGetValue(newKey, out list))
{
list = new List<int>();
myDict.Add(newKey, list);
}
list.Add(myNumber);
If the Dictionary is a field i would encapsulate the acces in a method:
Dictionary<string, List<int>> myDict = new Dictionary<string, List<int>>();
public void AddNumber(string key, int value)
{
List<int> list;
if(!myDict.TryGetValue(key, out list))
{
list = new List<int>();
myDict.Add(key, list);
}
list.Add(value);
}

If you use ConcurrentDictionary<T>, you can do this:
myDict.GetOrAdd(newKey, new List<int>()).Add(myNumber);

You can actually use the others' suggestions. By encapsulating the access in a method or even using ConcurrentDictionary.
But for me, I would have a custom dictionary so you can actually implement what myDict["entry"] does if it did not see an element.
Good thing with this is you have full control on how you would like this dictionary to behave.
class MyCustomDictionary<TKey, TValue> : IDictionary<TKey, TValue>
where TValue : class, new()
{
private Dictionary<TKey, TValue> _dictionary;
public MyCustomDictionary()
{
_dictionary = new Dictionary<TKey, TValue>();
}
public TValue this[TKey key] // this is what's important
{
get
{
TValue val;
if (!_dictionary.TryGetValue(key, out val)) // if there is no element for that key, add a new element and return it
{
_dictionary.Add(key, new TValue());
return _dictionary[key];
}
else // else return the found element
{
return val;
}
}
set
{
_dictionary[key] = value;
}
}
public void Add(TKey key, TValue value)
{
_dictionary.Add(key, value);
}
public bool ContainsKey(TKey key)
{
return _dictionary.ContainsKey(key);
}
public ICollection<TKey> Keys
{
get { return _dictionary.Keys; }
}
public bool Remove(TKey key)
{
return _dictionary.Remove(key);
}
public bool TryGetValue(TKey key, out TValue value)
{
return _dictionary.TryGetValue(key, out value);
}
public ICollection<TValue> Values
{
get { return _dictionary.Values; }
}
public void Add(KeyValuePair<TKey, TValue> item)
{
_dictionary.Add(item.Key, item.Value);
}
public void Clear()
{
_dictionary.Clear();
}
public bool Contains(KeyValuePair<TKey, TValue> item)
{
return _dictionary.Contains(item);
}
public void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
{
_dictionary.ToList().CopyTo(array, arrayIndex); // do you need this? you can leave this :)
}
public int Count
{
get { return _dictionary.Count; }
}
public bool IsReadOnly
{
get { return false; }
}
public bool Remove(KeyValuePair<TKey, TValue> item)
{
return _dictionary.Remove(item.Key);
}
public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
{
return _dictionary.GetEnumerator();
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
return _dictionary.GetEnumerator();
}
}
Then you use it like:
MyCustomDictionary<string, List<int>> myCustomDict = new MyCustomDictionary<int, List<int>>();
// return a new List of int
var someElementThatIsNotFound = myCustomDict["keyThatIsNonExistent"];

You can use TryGetValue method: if there's the key in the dictionary
you should just add the value into the list; otherwise you should
add a list with a value:
List<int> list
if (myDict.TryGetValue(newKey, out list))
list.Add(myNumber);
else
myDict.Add(newKey, new List<int>() { myNumber });

Lots of good answers already. I implemented an extension method for this exact reason:
public static TVALUE GetOrSet<TKEY, TVALUE>(this IDictionary<TKEY, TVALUE> self,
TKEY key,
Func<TVALUE> defaultValue)
{
TVALUE value;
if (!self.TryGetValue(key, out value))
{
value = defaultValue();
self[key] = value;
}
return value;
} // eo GetOrSet
Note that it takes a function to assign the value if it is not present. Either way, the value will be returned. Usage:
var dict = new Dictionary<string, List<int>>();
List<int> ints = dict.GetOrSet("list1", () => return new List<int>());
ints.Add(1);
If you're not referencing it again, you could potentially be less verbose:
dict.GetOrSet("list1", () => return new List<int>()).Add(1);

ObservableDictionary for c#

I'm trying to use following implementation of the ObservableDictionary: ObservableDictionary (C#).
When I'm using following code while binding the dictionary to a DataGrid:
ObserveableDictionary<string,string> dd=new ObserveableDictionary<string,string>();
....
dd["aa"]="bb";
....
dd["aa"]="cc";
at dd["aa"]="cc"; I'm getting following exception
Index was out of range. Must be non-negative and less than the size of the
collection. Parameter name: index
This exception is thrown in CollectionChanged(this, new NotifyCollectionChangedEventArgs(action, newItem, oldItem) in the following method:
private void OnCollectionChanged(NotifyCollectionChangedAction action, KeyValuePair<TKey, TValue> newItem, KeyValuePair<TKey, TValue> oldItem)
{
OnPropertyChanged();
if (CollectionChanged != null) CollectionChanged(this, new NotifyCollectionChangedEventArgs(action, newItem, oldItem));
}
The index param seems to correspond to KeyValuePair<TKey, TValue> oldItem.
How can KeyValuePair<TKey, TValue> be out of range, and what should I do to make this work?

here's what I did in the end:
[Serializable]
public class ObservableKeyValuePair<TKey,TValue>:INotifyPropertyChanged
{
#region properties
private TKey key;
private TValue value;
public TKey Key
{
get { return key; }
set
{
key = value;
OnPropertyChanged("Key");
}
}
public TValue Value
{
get { return value; }
set
{
this.value = value;
OnPropertyChanged("Value");
}
}
#endregion
#region INotifyPropertyChanged Members
[field:NonSerialized]
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(name));
}
#endregion
}
[Serializable]
public class ObservableDictionary<TKey,TValue>:ObservableCollection<ObservableKeyValuePair<TKey,TValue>>, IDictionary<TKey,TValue>
{
#region IDictionary<TKey,TValue> Members
public void Add(TKey key, TValue value)
{
if (ContainsKey(key))
{
throw new ArgumentException("The dictionary already contains the key");
}
base.Add(new ObservableKeyValuePair<TKey, TValue>() {Key = key, Value = value});
}
public bool ContainsKey(TKey key)
{
//var m=base.FirstOrDefault((i) => i.Key == key);
var r = ThisAsCollection().FirstOrDefault((i) => Equals(key, i.Key));
return !Equals(default(ObservableKeyValuePair<TKey, TValue>), r);
}
bool Equals<TKey>(TKey a, TKey b)
{
return EqualityComparer<TKey>.Default.Equals(a, b);
}
private ObservableCollection<ObservableKeyValuePair<TKey, TValue>> ThisAsCollection()
{
return this;
}
public ICollection<TKey> Keys
{
get { return (from i in ThisAsCollection() select i.Key).ToList(); }
}
public bool Remove(TKey key)
{
var remove = ThisAsCollection().Where(pair => Equals(key, pair.Key)).ToList();
foreach (var pair in remove)
{
ThisAsCollection().Remove(pair);
}
return remove.Count > 0;
}
public bool TryGetValue(TKey key, out TValue value)
{
value = default(TValue);
var r = GetKvpByTheKey(key);
if (!Equals(r, default(ObservableKeyValuePair<TKey, TValue>)))
{
return false;
}
value = r.Value;
return true;
}
private ObservableKeyValuePair<TKey, TValue> GetKvpByTheKey(TKey key)
{
return ThisAsCollection().FirstOrDefault((i) => i.Key.Equals(key));
}
public ICollection<TValue> Values
{
get { return (from i in ThisAsCollection() select i.Value).ToList(); }
}
public TValue this[TKey key]
{
get
{
TValue result;
if (!TryGetValue(key,out result))
{
throw new ArgumentException("Key not found");
}
return result;
}
set
{
if (ContainsKey(key))
{
GetKvpByTheKey(key).Value = value;
}
else
{
Add(key, value);
}
}
}
#endregion
#region ICollection<KeyValuePair<TKey,TValue>> Members
public void Add(KeyValuePair<TKey, TValue> item)
{
Add(item.Key, item.Value);
}
public bool Contains(KeyValuePair<TKey, TValue> item)
{
var r = GetKvpByTheKey(item.Key);
if (Equals(r, default(ObservableKeyValuePair<TKey, TValue>)))
{
return false;
}
return Equals(r.Value, item.Value);
}
public void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
{
throw new NotImplementedException();
}
public bool IsReadOnly
{
get { return false; }
}
public bool Remove(KeyValuePair<TKey, TValue> item)
{
var r = GetKvpByTheKey(item.Key);
if (Equals(r, default(ObservableKeyValuePair<TKey, TValue>)))
{
return false;
}
if (!Equals(r.Value,item.Value))
{
return false ;
}
return ThisAsCollection().Remove(r);
}
#endregion
#region IEnumerable<KeyValuePair<TKey,TValue>> Members
public new IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
{
return (from i in ThisAsCollection() select new KeyValuePair<TKey, TValue>(i.Key, i.Value)).ToList().GetEnumerator();
}
#endregion
}
This implementation looks and feels like dictionary to the user and like ObservableCollection to WPF

Similar data structure, to bind to Dictionary type collection
http://drwpf.com/blog/2007/09/16/can-i-bind-my-itemscontrol-to-a-dictionary/
It provides a new Data structure ObservableDictionary and fires PropertyChanged in case of any change to underlying Dictionary.

I ended up writing a class to hold the Key-Value pair and using a collection of that class. I'm using Caliburn Micro which is where the BindableCollection comes from, but an ObservableCollection should work the same way. I use the MVVM pattern.
the viewmodel
using Caliburn.Micro;
private BindableCollection<KeyValuePair> _items;
public BindableCollection<KeyValuePair> Items
{
get { return _items; }
set
{
if (_items != value)
{
_items = value;
NotifyOfPropertyChange(() => Items);
}
}
}
the custom keyValuePair
public class KeyValuePair
{
public string Key { get; set; }
public string Value { get; set; }
}
and in the view
<ItemsControl ItemsSource="{Binding Items}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="2*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<TextBox Grid.Column="0"
Text="{Binding Key, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
<TextBox Grid.Column="1"
Text="{Binding Value, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
It bothers me that I can't just bind to a dictionary, but I find this much easier and cleaner than writing an ObservableDictionary from scratch and worrying about the change notifications.

ObservableDictionary was added to the .Net Framework at version 4.5:-
https://zamjad.wordpress.com/2012/10/12/observabledictionary-in-net-4-5/
Here is a link to the latest source code:-
https://referencesource.microsoft.com/#PresentationFramework/src/Framework/MS/Internal/Annotations/ObservableDictionary.cs

I first created a class called "ConcurrentObservableCollection" in which i extended the ObservableCollection functions.
public class ConcurrentObservableCollection<T> : ObservableCollection<T>
{
private readonly object _lock = new object();
public new void Add(T value)
{
lock (_lock)
{
base.Add(value);
}
}
public List<T> ToList()
{
lock (_lock)
{
var copyList = new List<T>();
copyList.AddRange(base.Items);
return copyList;
}
}
public new IEnumerator<T> GetEnumerator()
{
lock (_lock)
{
return base.GetEnumerator();
}
}
public new bool Remove(T item)
{
lock (_lock)
{
return base.Remove(item);
}
}
public new void Move(int oldIndex, int newIndex)
{
lock (_lock)
{
base.Move(oldIndex, newIndex);
}
}
public new bool Contains(T item)
{
lock (_lock)
{
return base.Contains(item);
}
}
public new void Insert(int index, T item)
{
lock (_lock)
{
base.Insert(index, item);
}
}
public new int Count()
{
lock (_lock)
{
return base.Count;
}
}
public new void Clear()
{
lock (_lock)
{
base.Clear();
}
}
public new T this[int index]
{
get
{
lock (_lock)
{
return base[index];
}
}
}
}
Then i replaced the exisitng "ObservabeCollection" with my new "ConcurrentObservableCollection"

Even I am using the ObservableDictionary of github, I also faced this exception. I had declared the dictionary variable at class level later I tried to create a new instance in the method where it was getting accessed.
OldCode which gave exception:
public class CName
{
ObservableDictionary<string, string> _classVariableDictionary = new ObservableDictionary<string, string>();
}
NewCode which worked:
public void MethodName()
{
ObservableDictionary<string, string> _localVariableDictionary = new ObservableDictionary<string, string>();
}

Making a SortedList readonly

I often have classes exposing lists as ReadOnlyCollection<T>s, i.e.
public class Class
{
List<string> list;
public ReadOnlyCollection<string> TheList
{
get { return list.AsReadOnly(); }
}
}
What's the best way to do this for an IDictionary<T,U> such as a SortedList<string, string>?

public class ReadOnlyDictionary<TKey, TValue> : IDictionary<TKey, TValue>
{
private readonly IDictionary<TKey, TValue> sourceDictionary;
public ICollection<TKey> Keys
{
get { return sourceDictionary.Keys; }
}
public ICollection<TValue> Values
{
get { return sourceDictionary.Values; }
}
public TValue this[TKey key]
{
get { return sourceDictionary[key]; }
set { throw new NotSupportedException(); }
}
public int Count
{
get { return sourceDictionary.Count; }
}
public bool IsReadOnly
{
get { return true; }
}
public ReadOnlyDictionary(IDictionary<TKey, TValue> sourceDictionary)
{
AssertUtilities.ArgumentNotNull(sourceDictionary, "sourceDictionary");
this.sourceDictionary = sourceDictionary;
}
void IDictionary<TKey, TValue>.Add(TKey key, TValue value)
{
throw new NotSupportedException();
}
public bool ContainsKey(TKey key)
{
return sourceDictionary.ContainsKey(key);
}
bool IDictionary<TKey, TValue>.Remove(TKey key)
{
throw new NotSupportedException();
}
public bool TryGetValue(TKey key, out TValue value)
{
return sourceDictionary.TryGetValue(key, out value);
}
void ICollection<KeyValuePair<TKey, TValue>>.Add(KeyValuePair<TKey, TValue> item)
{
throw new NotSupportedException();
}
void ICollection<KeyValuePair<TKey, TValue>>.Clear()
{
throw new NotSupportedException();
}
public bool Contains(KeyValuePair<TKey, TValue> item)
{
return sourceDictionary.Contains(item);
}
public void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
{
sourceDictionary.CopyTo(array, arrayIndex);
}
bool ICollection<KeyValuePair<TKey, TValue>>.Remove(KeyValuePair<TKey, TValue> item)
{
throw new NotSupportedException();
}
public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
{
return sourceDictionary.GetEnumerator();
}
IEnumerator IEnumerable.GetEnumerator()
{
return ((IEnumerable)sourceDictionary).GetEnumerator();
}
}
[Edit]
#Simon Buchan and #Cory Nelson pointed out that it is better to use implicit interface implementation for those methods that are not supported. Updated the code accordingly.

Create a ReadOnlyDictionary class that implements IDictionary as a wrapper around an internal Dictionary instance. For the methods that would modify the dictionary, throw an exception. Implement IsReadOnly to return true. Implement all other methods to pass through to the internal Dictionary instance.

You can do it with standard LINQ methods.
Create you source list:
List<String> myList = new List<String>() { "A", "B", "C" };
Project your list into a dictionary using .ToDictionary linq extension method:
var myDictionary = myList.ToDictionary(listItem => listItem);
Note: The lambda expression peeks a key from you list (rembember that dictionary can only contain unique keys; otherwise consider the use of ILookup which represents a dictionary of list).
Reform your dictionary to a SortedDictionary instance:
var mySortedDictionary = new SortedDictionary<string, string>(myDictionary);
Expose your sorted dictionary as an IReadOnlyDictionary interface as follows:
public IReadOnlyDictionary MemberDictionary { get; private set; );
// ...somewhere in your constructor or class's initialization method...
this.MemberDictionary = mySortedDictionary;