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How to: Convert from a .NET Collection to a STL/CLR Container

This topic shows how to convert .NET collections to their equivalent STL/CLR containers. As an example we show how to convert a .NET List<T> to a STL/CLR vector and how to convert a .NET Dictionary<TKey, TValue> to a STL/CLR map, but the procedure is similar for all collections and containers.

To create a container from a collection

  • To convert an entire collection, create a STL/CLR container and pass the collection to the constructor.

    The first example demonstrates this procedure.

-OR-

  1. Create a generic STL/CLR container by creating a collection_adapter object. This template class takes a .NET collection interface as an argument. To verify which interfaces are supported, see collection_adapter (STL/CLR).

  2. Copy the contents of the .NET collection to the container. This can be done by using a STL/CLR algorithm, or by iterating over the .NET collection and inserting a copy of each element into the STL/CLR container.

    The second example demonstrates this procedure.

In this example, we create a generic List<T> and add 5 elements to it. Then, we create a vector using the constructor that takes a IEnumerable<T> as an argument.

// cliext_convert_list_to_vector.cpp
// compile with: /clr

#include <cliext/adapter>
#include <cliext/algorithm>
#include <cliext/vector>

using namespace System;
using namespace System::Collections;
using namespace System::Collections::Generic;

int main(array<System::String ^> ^args)
{
    List<int> ^primeNumbersColl = gcnew List<int>();
    primeNumbersColl->Add(2);
    primeNumbersColl->Add(3);
    primeNumbersColl->Add(5);
    primeNumbersColl->Add(7);
    primeNumbersColl->Add(11);

    cliext::vector<int> ^primeNumbersCont =
        gcnew cliext::vector<int>(primeNumbersColl);

    Console::WriteLine("The contents of the cliext::vector are:");
    cliext::vector<int>::const_iterator it;
    for (it = primeNumbersCont->begin(); it != primeNumbersCont->end(); it++)
    {
        Console::WriteLine(*it);
    }
}
The contents of the cliext::vector are:
2
3
5
7
11

In this example, we create a generic Dictionary<TKey, TValue> and add 5 elements to it. Then, we create a collection_adapter to wrap the Dictionary<TKey, TValue> as a simple STL/CLR container. Finally, we create a map and copy the contents of the Dictionary<TKey, TValue> to the map by iterating over the collection_adapter. During this process, we create a new pair by using the make_pair function, and insert the new pair directly into the map.

// cliext_convert_dictionary_to_map.cpp
// compile with: /clr

#include <cliext/adapter>
#include <cliext/algorithm>
#include <cliext/map>

using namespace System;
using namespace System::Collections;
using namespace System::Collections::Generic;

int main(array<System::String ^> ^args)
{
    System::Collections::Generic::Dictionary<float, int> ^dict =
        gcnew System::Collections::Generic::Dictionary<float, int>();
    dict->Add(42.0, 42);
    dict->Add(13.0, 13);
    dict->Add(74.0, 74);
    dict->Add(22.0, 22);
    dict->Add(0.0, 0);

    cliext::collection_adapter<System::Collections::Generic::IDictionary<float, int>> dictAdapter(dict);
    cliext::map<float, int> aMap;
    for each (KeyValuePair<float, int> ^kvp in dictAdapter)
    {
        cliext::pair<float, int> aPair = cliext::make_pair(kvp->Key, kvp->Value);
        aMap.insert(aPair);
    }

    Console::WriteLine("The contents of the cliext::map are:");
    cliext::map<float, int>::const_iterator it;
    for (it = aMap.begin(); it != aMap.end(); it++)
    {
        Console::WriteLine("Key: {0:F} Value: {1}", it->first, it->second);
    }
}
The contents of the cliext::map are:
Key: 0.00 Value: 0
Key: 13.00 Value: 13
Key: 22.00 Value: 22
Key: 42.00 Value: 42
Key: 74.00 Value: 74

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