Adding CartesianProduct (#14)

* Adding CartesianProduct extension method.

Author: wbaldoumas

documentation/Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-).md

@@ -1,31 +1,31 @@
-#### [Atrea.Extensions](./index.md 'index')
-### [Atrea.Extensions](./Atrea-Extensions.md 'Atrea.Extensions').[DictionaryExtensions](./Atrea-Extensions-DictionaryExtensions.md 'Atrea.Extensions.DictionaryExtensions')
-## DictionaryExtensions.Merge<TKey,TValue>(System.Collections.Generic.IDictionary<TKey,TValue>, System.Collections.Generic.IDictionary<TKey,TValue>) Method
-Merge the new dictionary into the source directory, overwriting on duplicate keys.  
-If the new dictionary is null or empty, the first dictionary is returned unmodified.  
-If the source dictionary is null or empty, the new dictionary is returned unmodified.  
-```csharp
-public static System.Collections.Generic.IDictionary<TKey,TValue> Merge<TKey,TValue>(this System.Collections.Generic.IDictionary<TKey,TValue> source, System.Collections.Generic.IDictionary<TKey,TValue> newDictionary);
-```
-#### Type parameters
-<a name='Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TKey'></a>
-`TKey`  
-The dictionary key type  
-  
-<a name='Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TValue'></a>
-`TValue`  
-The dictionary value type  
-  
-#### Parameters
-<a name='Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-source'></a>
-`source` [System.Collections.Generic.IDictionary&lt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')[TKey](#Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TKey 'Atrea.Extensions.DictionaryExtensions.Merge&lt;TKey,TValue&gt;(System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;, System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;).TKey')[,](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')[TValue](#Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TValue 'Atrea.Extensions.DictionaryExtensions.Merge&lt;TKey,TValue&gt;(System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;, System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;).TValue')[&gt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')  
-The dictionary of old values  
-  
-<a name='Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-newDictionary'></a>
-`newDictionary` [System.Collections.Generic.IDictionary&lt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')[TKey](#Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TKey 'Atrea.Extensions.DictionaryExtensions.Merge&lt;TKey,TValue&gt;(System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;, System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;).TKey')[,](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')[TValue](#Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TValue 'Atrea.Extensions.DictionaryExtensions.Merge&lt;TKey,TValue&gt;(System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;, System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;).TValue')[&gt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')  
-The dictionary with new values  
-  
-#### Returns
-[System.Collections.Generic.IDictionary&lt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')[TKey](#Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TKey 'Atrea.Extensions.DictionaryExtensions.Merge&lt;TKey,TValue&gt;(System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;, System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;).TKey')[,](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')[TValue](#Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TValue 'Atrea.Extensions.DictionaryExtensions.Merge&lt;TKey,TValue&gt;(System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;, System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;).TValue')[&gt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')  
-A merged dictionary whose keys are a union of the keys of the two dictionaries, and  
-whose values are drawn from the second dictionary if they are present, otherwise the first.  
+#### [Atrea.Extensions](./index.md 'index')
+### [Atrea.Extensions](./Atrea-Extensions.md 'Atrea.Extensions').[DictionaryExtensions](./Atrea-Extensions-DictionaryExtensions.md 'Atrea.Extensions.DictionaryExtensions')
+## DictionaryExtensions.Merge&lt;TKey,TValue&gt;(System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;, System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;) Method
+Merge the new dictionary into the source directory, overwriting on duplicate keys.  
+If the new dictionary is null or empty, the first dictionary is returned unmodified.  
+If the source dictionary is null or empty, the new dictionary is returned unmodified.  
+```csharp
+public static System.Collections.Generic.IDictionary<TKey,TValue> Merge<TKey,TValue>(this System.Collections.Generic.IDictionary<TKey,TValue> source, System.Collections.Generic.IDictionary<TKey,TValue> newDictionary);
+```
+#### Type parameters
+<a name='Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TKey'></a>
+`TKey`  
+The dictionary key type  
+  
+<a name='Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TValue'></a>
+`TValue`  
+The dictionary value type  
+  
+#### Parameters
+<a name='Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-source'></a>
+`source` [System.Collections.Generic.IDictionary&lt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')[TKey](#Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TKey 'Atrea.Extensions.DictionaryExtensions.Merge&lt;TKey,TValue&gt;(System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;, System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;).TKey')[,](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')[TValue](#Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TValue 'Atrea.Extensions.DictionaryExtensions.Merge&lt;TKey,TValue&gt;(System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;, System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;).TValue')[&gt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')  
+The dictionary of old values  
+  
+<a name='Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-newDictionary'></a>
+`newDictionary` [System.Collections.Generic.IDictionary&lt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')[TKey](#Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TKey 'Atrea.Extensions.DictionaryExtensions.Merge&lt;TKey,TValue&gt;(System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;, System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;).TKey')[,](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')[TValue](#Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TValue 'Atrea.Extensions.DictionaryExtensions.Merge&lt;TKey,TValue&gt;(System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;, System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;).TValue')[&gt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')  
+The dictionary with new values  
+  
+#### Returns
+[System.Collections.Generic.IDictionary&lt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')[TKey](#Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TKey 'Atrea.Extensions.DictionaryExtensions.Merge&lt;TKey,TValue&gt;(System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;, System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;).TKey')[,](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')[TValue](#Atrea-Extensions-DictionaryExtensions-Merge-TKey_TValue-(System-Collections-Generic-IDictionary-TKey_TValue-_System-Collections-Generic-IDictionary-TKey_TValue-)-TValue 'Atrea.Extensions.DictionaryExtensions.Merge&lt;TKey,TValue&gt;(System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;, System.Collections.Generic.IDictionary&lt;TKey,TValue&gt;).TValue')[&gt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IDictionary-2 'System.Collections.Generic.IDictionary`2')  
+A merged dictionary whose keys are a union of the keys of the two dictionaries, and  
+whose values are drawn from the second dictionary if they are present, otherwise the first.  

documentation/Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-).md

@@ -1,28 +1,28 @@
-#### [Atrea.Extensions](./index.md 'index')
-### [Atrea.Extensions](./Atrea-Extensions.md 'Atrea.Extensions').[DictionaryExtensions](./Atrea-Extensions-DictionaryExtensions.md 'Atrea.Extensions.DictionaryExtensions')
-## DictionaryExtensions.ToMultiLookup<TKey,TValue>(System.Collections.Generic.IEnumerable<TValue>, System.Func<TValue,TKey>) Method
-Create a lookup by key that maps to multiple items per key.  
-```csharp
-public static System.Collections.Generic.Dictionary<TKey,System.Collections.Generic.List<TValue>> ToMultiLookup<TKey,TValue>(this System.Collections.Generic.IEnumerable<TValue> source, System.Func<TValue,TKey> keyFunction);
-```
-#### Type parameters
-<a name='Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-TKey'></a>
-`TKey`  
-The dictionary key type  
-  
-<a name='Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-TValue'></a>
-`TValue`  
-The source item type  
-  
-#### Parameters
-<a name='Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-source'></a>
-`source` [System.Collections.Generic.IEnumerable&lt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IEnumerable-1 'System.Collections.Generic.IEnumerable`1')[TValue](#Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-TValue 'Atrea.Extensions.DictionaryExtensions.ToMultiLookup&lt;TKey,TValue&gt;(System.Collections.Generic.IEnumerable&lt;TValue&gt;, System.Func&lt;TValue,TKey&gt;).TValue')[&gt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IEnumerable-1 'System.Collections.Generic.IEnumerable`1')  
-The source enumeration  
-  
-<a name='Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-keyFunction'></a>
-`keyFunction` [System.Func&lt;](https://docs.microsoft.com/en-us/dotnet/api/System.Func-2 'System.Func`2')[TValue](#Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-TValue 'Atrea.Extensions.DictionaryExtensions.ToMultiLookup&lt;TKey,TValue&gt;(System.Collections.Generic.IEnumerable&lt;TValue&gt;, System.Func&lt;TValue,TKey&gt;).TValue')[,](https://docs.microsoft.com/en-us/dotnet/api/System.Func-2 'System.Func`2')[TKey](#Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-TKey 'Atrea.Extensions.DictionaryExtensions.ToMultiLookup&lt;TKey,TValue&gt;(System.Collections.Generic.IEnumerable&lt;TValue&gt;, System.Func&lt;TValue,TKey&gt;).TKey')[&gt;](https://docs.microsoft.com/en-us/dotnet/api/System.Func-2 'System.Func`2')  
-The function to map items to their keys  
-  
-#### Returns
-[System.Collections.Generic.Dictionary&lt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.Dictionary-2 'System.Collections.Generic.Dictionary`2')[TKey](#Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-TKey 'Atrea.Extensions.DictionaryExtensions.ToMultiLookup&lt;TKey,TValue&gt;(System.Collections.Generic.IEnumerable&lt;TValue&gt;, System.Func&lt;TValue,TKey&gt;).TKey')[,](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.Dictionary-2 'System.Collections.Generic.Dictionary`2')[System.Collections.Generic.List&lt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.List-1 'System.Collections.Generic.List`1')[TValue](#Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-TValue 'Atrea.Extensions.DictionaryExtensions.ToMultiLookup&lt;TKey,TValue&gt;(System.Collections.Generic.IEnumerable&lt;TValue&gt;, System.Func&lt;TValue,TKey&gt;).TValue')[&gt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.List-1 'System.Collections.Generic.List`1')[&gt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.Dictionary-2 'System.Collections.Generic.Dictionary`2')  
-A dictionary mapping keys to an enumeration of source items with that key  
+#### [Atrea.Extensions](./index.md 'index')
+### [Atrea.Extensions](./Atrea-Extensions.md 'Atrea.Extensions').[DictionaryExtensions](./Atrea-Extensions-DictionaryExtensions.md 'Atrea.Extensions.DictionaryExtensions')
+## DictionaryExtensions.ToMultiLookup&lt;TKey,TValue&gt;(System.Collections.Generic.IEnumerable&lt;TValue&gt;, System.Func&lt;TValue,TKey&gt;) Method
+Create a lookup by key that maps to multiple items per key.  
+```csharp
+public static System.Collections.Generic.Dictionary<TKey,System.Collections.Generic.List<TValue>> ToMultiLookup<TKey,TValue>(this System.Collections.Generic.IEnumerable<TValue> source, System.Func<TValue,TKey> keyFunction);
+```
+#### Type parameters
+<a name='Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-TKey'></a>
+`TKey`  
+The dictionary key type  
+  
+<a name='Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-TValue'></a>
+`TValue`  
+The source item type  
+  
+#### Parameters
+<a name='Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-source'></a>
+`source` [System.Collections.Generic.IEnumerable&lt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IEnumerable-1 'System.Collections.Generic.IEnumerable`1')[TValue](#Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-TValue 'Atrea.Extensions.DictionaryExtensions.ToMultiLookup&lt;TKey,TValue&gt;(System.Collections.Generic.IEnumerable&lt;TValue&gt;, System.Func&lt;TValue,TKey&gt;).TValue')[&gt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.IEnumerable-1 'System.Collections.Generic.IEnumerable`1')  
+The source enumeration  
+  
+<a name='Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-keyFunction'></a>
+`keyFunction` [System.Func&lt;](https://docs.microsoft.com/en-us/dotnet/api/System.Func-2 'System.Func`2')[TValue](#Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-TValue 'Atrea.Extensions.DictionaryExtensions.ToMultiLookup&lt;TKey,TValue&gt;(System.Collections.Generic.IEnumerable&lt;TValue&gt;, System.Func&lt;TValue,TKey&gt;).TValue')[,](https://docs.microsoft.com/en-us/dotnet/api/System.Func-2 'System.Func`2')[TKey](#Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-TKey 'Atrea.Extensions.DictionaryExtensions.ToMultiLookup&lt;TKey,TValue&gt;(System.Collections.Generic.IEnumerable&lt;TValue&gt;, System.Func&lt;TValue,TKey&gt;).TKey')[&gt;](https://docs.microsoft.com/en-us/dotnet/api/System.Func-2 'System.Func`2')  
+The function to map items to their keys  
+  
+#### Returns
+[System.Collections.Generic.Dictionary&lt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.Dictionary-2 'System.Collections.Generic.Dictionary`2')[TKey](#Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-TKey 'Atrea.Extensions.DictionaryExtensions.ToMultiLookup&lt;TKey,TValue&gt;(System.Collections.Generic.IEnumerable&lt;TValue&gt;, System.Func&lt;TValue,TKey&gt;).TKey')[,](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.Dictionary-2 'System.Collections.Generic.Dictionary`2')[System.Collections.Generic.List&lt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.List-1 'System.Collections.Generic.List`1')[TValue](#Atrea-Extensions-DictionaryExtensions-ToMultiLookup-TKey_TValue-(System-Collections-Generic-IEnumerable-TValue-_System-Func-TValue_TKey-)-TValue 'Atrea.Extensions.DictionaryExtensions.ToMultiLookup&lt;TKey,TValue&gt;(System.Collections.Generic.IEnumerable&lt;TValue&gt;, System.Func&lt;TValue,TKey&gt;).TValue')[&gt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.List-1 'System.Collections.Generic.List`1')[&gt;](https://docs.microsoft.com/en-us/dotnet/api/System.Collections.Generic.Dictionary-2 'System.Collections.Generic.Dictionary`2')  
+A dictionary mapping keys to an enumeration of source items with that key