Reading orders from the marketplace API is done with the IMarketplaceReader interface, implemented by MarketplaceReader. The IMarketplaceReader interface has IntelliSense summaries to help you understand what each method is used for, but, we’ll call out a few of them here as well.

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Usage

All IMarketplaceReader methods are asynchronous Tasks and can be awaited directly and/or you can subscribe to the associated events.

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Methods

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ListCurrencies

Fetch an array of whitelisted Currencies that can be used in your game’s marketplace. 
IMarketplaceReader reader = new MarketplaceReader(_chain);

// optionally subscribe to callback events
reader.OnListCurrenciesReturn += OnCurrenciesFetched; 
reader.OnListCurrenciesError += OnCurrencyFetchError;

Currency[] currencies = await reader.ListCurrencies();
// or if only listening to event handlers
reader.ListCurrencies();
...


private void OnCurrenciesFetched(Currency[] fetchedCurrencies) {
    // Do something
}

private void OnCurrencyFetchError(string error) {
    // Do something
}

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Fetching Listings

There are a few different ways to fetch listings.
  1. ListCollectibleListingsWithLowestPricedListingsFirst is used to get the listings associated with a given contract address. The listings will be ordered with the lowest priced listings first. In addition, only the lowest priced listing for each collectible (i.e. each token id) will be returned.
IMarketplaceReader reader = new MarketplaceReader(_chain);
ListCollectiblesReturn collectiblesReturn = await reader.ListCollectibleListingsWithLowestPricedListingsFirst(myCollectionContractAddress);
CollectibleOrder[] orders = collectiblesReturn.collectibles;
Optionally, you can provide a CollectiblesFilter to apply filters on your query. This request uses pagination. If you’re dealing with a rather small collection and don’t want to deal with pagination, you can use the ListAllCollectibleListingsWithLowestPricedListingsFirst helper function; this will handle the pagination for you and continue to make requests until all the relevant CollectibleOrders have been retrieved. You can also optionally subscribe to the OnListCollectibleOrdersReturn and OnListCollectibleOrdersError events in order to handle the responses elsewhere.
  1. GetLowestPriceListingForCollectible and GetHighestPriceListingForCollectible can be used to fetch the lowest and highest priced listing for a collectible respectively.
IMarketplaceReader reader = new MarketplaceReader(_chain);
Order lowestPricedListing = await reader.GetLowestPriceListingForCollectible(collectionContractAddress, tokenId);
Order highestPricedListing = await reader.GetHighestPriceListingForCollectible(collectionContractAddress, tokenId);
Optionally, you can provide an OrderFilter to apply filters on your query. Additionally, you have the option to subscribe to the OnGetCollectibleOrderReturn and OnGetCollectibleOrderError events in order to handle the response elsewhere.
  1. ListListingsForCollectible is used to get all of the listings for a given Collectible.
IMarketplaceReader reader = new MarketplaceReader(_chain);
ListCollectibleListingsReturn listingsReturn = await reader.ListListingsForCollectible(collectionContractAddress, tokenId);
Order[] listings = listingsReturn.listings;
Optionally, you can provide an OrderFilter to apply filters on your query. This request uses pagination. If you’re dealing with a rather small set of listings and don’t want to deal with pagination, you can use the ListAllListingsForCollectible helper function; this will handle the pagination for you and continue to make requests until all the relevant Orders have been retrieved. Additionally, you have the option to subscribe to the OnListCollectibleListingsReturn and OnListCollectibleListingsError events in order to handle the response elsewhere.
  1. ListAllPurchasableListings is a convenience helper method that can be used to ListAllCollectibleListingsWithLowestPricedListingsFirst, filtering for listings not created by purchasableBy. Then, using a ChainIndexer for the configured Chain to fetch purchasableBy’s token balances and removing any listings they cannot afford to purchase without swapping.
IMarketplaceReader reader = new MarketplaceReader(_chain);
CollectibleOrder[] purchasableListings = await reader.ListAllPurchasableListings(userWalletAddress, collectionContractAddress);
This method will handle pagination for you, continuing to make requests until all CollectibleOrders have been fetched. Be careful to use it on collections with a small amount of listings (as with other helper methods that handle pagination for you) so that you do not use too much memory. This method’s implementation can also serve as an example for how you can work with the Indexer in conjunction with the peer to peer marketplaces.

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Fetching Offers

There are a few different ways to fetch offers. They all function similarly to their listing-equivalent methods.
  1. ListCollectibleOffersWithHighestPricedOfferFirst is used to get the offers associated with a given contract address. The listings will be ordered with the highest priced offer first. In addition, only the highest priced offer for each collectible (i.e. each token id) will be returned.
IMarketplaceReader reader = new MarketplaceReader(_chain);
ListCollectiblesReturn collectiblesReturn = await reader.ListCollectibleOffersWithHighestPricedOfferFirst(myCollectionContractAddress);
CollectibleOrder[] orders = collectiblesReturn.collectibles;
Optionally, you can provide a CollectiblesFilter to apply filters on your query. This request uses pagination. If you’re dealing with a rather small collection and don’t want to deal with pagination, you can use the ListAllCollectibleOffersWithHighestPricedOfferFirst helper function; this will handle the pagination for you and continue to make requests until all the relevant CollectibleOrders have been retrieved. You can also optionally subscribe to the OnListCollectibleOrdersReturn and OnListCollectibleOrdersError events in order to handle the responses elsewhere.
  1. GetLowestPriceOfferForCollectible and GetHighestPriceOfferForCollectible can be used to fetch the lowest and highest priced offer for a collectible respectively.
IMarketplaceReader reader = new MarketplaceReader(_chain);
Order lowestPricedOffer = await reader.GetLowestPriceOfferForCollectible(collectionContractAddress, tokenId);
Order highestPricedOffer = await reader.GetHighestPriceOfferForCollectible(collectionContractAddress, tokenId);
Optionally, you can provide an OrderFilter to apply filters on your query. Additionally, you have the option to subscribe to the OnGetCollectibleOrderReturn and OnGetCollectibleOrderError events in order to handle the response elsewhere.
  1. ListOffersForCollectible is used to get all of the offers for a given Collectible.
IMarketplaceReader reader = new MarketplaceReader(_chain);
ListCollectibleOffersReturn offersReturn = await reader.ListOffersForCollectible(collectionContractAddress, tokenId);
Order[] offers = offersReturn.offers;
Optionally, you can provide an OrderFilter to apply filters on your query. This request uses pagination. If you’re dealing with a rather small set of offers and don’t want to deal with pagination, you can use the ListAllOffersForCollectible helper function; this will handle the pagination for you and continue to make requests until all the relevant Orders have been retrieved. Additionally, you have the option to subscribe to the OnListCollectibleOffersReturn and OnListCollectibleOffersError events in order to handle the response elsewhere.
  1. ListAllSellableOffers is a convenience helper method that can be used to ListAllCollectibleOffersWithHighestPricedOfferFirst, filtering for offers not created by sellableBy and where sellableBy has at least one of the collectibles being requested.
IMarketplaceReader reader = new MarketplaceReader(_chain);
CollectibleOrder[] sellableOffers = await reader.ListAllSellableOffers(userWalletAddress, collectionContractAddress);
This method will handle pagination for you, continuing to make requests until all CollectibleOrders have been fetched. Be careful to use it on collections with a small amount of offers (as with other helper methods that handle pagination for you) so that you do not use too much memory. This method’s implementation can also serve as an example for how you can work with CollectiblesFilters.

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Conclusion

Using the IMarketplaceReader, you should have sufficient means to query the marketplace API and assemble a marketplace UI for your users to browse. In general, most marketplaces will rely primarily on the ListCollectibleListingsWithLowestPricedListingsFirst and ListCollectibleOffersWithHighestPricedOfferFirst methods and CollectiblesFilter for querying/filtering listings and orders respectively, with the remaining methods being primarily useful during the checkout process.