Fix all listing blockers: real policy IDs, merchant location, shared HttpClient

Business policies: EnsurePoliciesAndLocationAsync fetches fulfillment,
payment and return policy IDs from the seller's eBay Account API on
first post and caches them for the session. Uses the first policy of
each type; gives a clear error pointing to My eBay → Business policies
if none are configured.

Merchant location: checks for existing locations via
GET /sell/inventory/v1/location; if none found, creates a 'home'
location using the seller's postcode. Location key is cached so the
check only runs once. Cache cleared on disconnect so it works
correctly after switching accounts.

CreateOfferAsync now sends real fulfillmentPolicyId / paymentPolicyId /
returnPolicyId instead of hardcoded policy name strings, and uses the
resolved merchantLocationKey instead of the hardcoded "home" string.

Removed BuildListingPolicies (inline shipping service codes no longer
needed; shipping is governed by the fulfillment policy).

Shared HttpClient: replaced BuildClient() (which returned a new
HttpClient per call) with a static _http client and MakeRequest()
helper that creates a pre-authorised HttpRequestMessage. UploadSinglePhotoAsync
likewise uses a static _photoHttp client and HttpRequestMessage instead
of new HttpClient() per photo.

Removed placeholder ExternalPictureURL from Trading API SOAP body.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

EbayListingTool/Services/EbayListingService.cs

@@ -12,17 +12,39 @@ public class EbayListingService
     private readonly EbayAuthService _auth;
     private readonly EbayCategoryService _categoryService;
 
+    // Shared clients — avoids socket exhaustion from per-call `new HttpClient()`
+    private static readonly HttpClient _http      = new(); // REST / Inventory / Account APIs
+    private static readonly HttpClient _photoHttp = new(); // Trading API (photo upload)
+
+    // Per-session cache of eBay account IDs — fetched once, reused for every listing
+    private string? _fulfillmentPolicyId;
+    private string? _paymentPolicyId;
+    private string? _returnPolicyId;
+    private string? _merchantLocationKey;
+
     public EbayListingService(EbayAuthService auth, EbayCategoryService categoryService)
     {
         _auth = auth;
         _categoryService = categoryService;
     }
 
+    /// <summary>Call when the user disconnects so stale IDs are not reused after re-login.</summary>
+    public void ClearCache()
+    {
+        _fulfillmentPolicyId = null;
+        _paymentPolicyId     = null;
+        _returnPolicyId      = null;
+        _merchantLocationKey = null;
+    }
+
     public async Task<string> PostListingAsync(ListingDraft draft)
     {
         var token = await _auth.GetValidAccessTokenAsync();
 
-        // 1. Upload photos and get URLs
+        // Resolve business policies and merchant location before touching inventory/offers
+        await EnsurePoliciesAndLocationAsync(token, draft.Postcode);
+
+        // 1. Upload photos and get eBay-hosted URLs
         var imageUrls = await UploadPhotosAsync(draft.PhotoPaths, token);
 
         // 2. Resolve category if not set
@@ -51,23 +73,148 @@ public class EbayListingService
         return draft.EbayListingUrl;
     }
 
+    // ---- Setup: policies + location ----
+
+    /// <summary>
+    /// Fetches fulfillment, payment and return policy IDs from the seller's eBay account,
+    /// and ensures at least one merchant location exists (creating "home" from the seller's
+    /// postcode if needed). Results are cached for the session.
+    /// </summary>
+    private async Task EnsurePoliciesAndLocationAsync(string token, string postcode)
+    {
+        var baseUrl = _auth.BaseUrl;
+
+        if (_fulfillmentPolicyId == null)
+        {
+            using var req = MakeRequest(HttpMethod.Get,
+                $"{baseUrl}/sell/account/v1/fulfillment_policy?marketplace_id=EBAY_GB", token);
+            var res  = await _http.SendAsync(req);
+            var json = await res.Content.ReadAsStringAsync();
+
+            if (!res.IsSuccessStatusCode)
+                throw new HttpRequestException(
+                    $"Could not fetch fulfillment policies ({(int)res.StatusCode}): {json}");
+
+            var arr = JObject.Parse(json)["fulfillmentPolicies"] as JArray;
+            _fulfillmentPolicyId = arr?.Count > 0
+                ? arr[0]["fulfillmentPolicyId"]?.ToString()
+                : null;
+
+            if (_fulfillmentPolicyId == null)
+                throw new InvalidOperationException(
+                    "No fulfillment policy found on your eBay account.\n\n" +
+                    "Please set one up in My eBay → Account → Business policies, then try again.");
+        }
+
+        if (_paymentPolicyId == null)
+        {
+            using var req = MakeRequest(HttpMethod.Get,
+                $"{baseUrl}/sell/account/v1/payment_policy?marketplace_id=EBAY_GB", token);
+            var res  = await _http.SendAsync(req);
+            var json = await res.Content.ReadAsStringAsync();
+
+            if (!res.IsSuccessStatusCode)
+                throw new HttpRequestException(
+                    $"Could not fetch payment policies ({(int)res.StatusCode}): {json}");
+
+            var arr = JObject.Parse(json)["paymentPolicies"] as JArray;
+            _paymentPolicyId = arr?.Count > 0
+                ? arr[0]["paymentPolicyId"]?.ToString()
+                : null;
+
+            if (_paymentPolicyId == null)
+                throw new InvalidOperationException(
+                    "No payment policy found on your eBay account.\n\n" +
+                    "Please set one up in My eBay → Account → Business policies, then try again.");
+        }
+
+        if (_returnPolicyId == null)
+        {
+            using var req = MakeRequest(HttpMethod.Get,
+                $"{baseUrl}/sell/account/v1/return_policy?marketplace_id=EBAY_GB", token);
+            var res  = await _http.SendAsync(req);
+            var json = await res.Content.ReadAsStringAsync();
+
+            if (!res.IsSuccessStatusCode)
+                throw new HttpRequestException(
+                    $"Could not fetch return policies ({(int)res.StatusCode}): {json}");
+
+            var arr = JObject.Parse(json)["returnPolicies"] as JArray;
+            _returnPolicyId = arr?.Count > 0
+                ? arr[0]["returnPolicyId"]?.ToString()
+                : null;
+
+            if (_returnPolicyId == null)
+                throw new InvalidOperationException(
+                    "No return policy found on your eBay account.\n\n" +
+                    "Please set one up in My eBay → Account → Business policies, then try again.");
+        }
+
+        if (_merchantLocationKey == null)
+        {
+            using var req = MakeRequest(HttpMethod.Get,
+                $"{baseUrl}/sell/inventory/v1/location", token);
+            var res  = await _http.SendAsync(req);
+            var json = await res.Content.ReadAsStringAsync();
+
+            if (res.IsSuccessStatusCode)
+            {
+                var arr  = JObject.Parse(json)["locations"] as JArray;
+                _merchantLocationKey = arr?.Count > 0
+                    ? arr[0]["merchantLocationKey"]?.ToString()
+                    : null;
+            }
+
+            // No existing locations — create one from the seller's postcode
+            if (_merchantLocationKey == null)
+            {
+                await CreateMerchantLocationAsync(token, postcode);
+                _merchantLocationKey = "home";
+            }
+        }
+    }
+
+    private async Task CreateMerchantLocationAsync(string token, string postcode)
+    {
+        if (string.IsNullOrWhiteSpace(postcode))
+            postcode = "N/A"; // eBay allows this when postcode is genuinely unknown
+
+        var body = new
+        {
+            location = new
+            {
+                address = new { postalCode = postcode, country = "GB" }
+            },
+            locationTypes      = new[] { "WAREHOUSE" },
+            name               = "Home",
+            merchantLocationStatus = "ENABLED"
+        };
+
+        using var req = MakeRequest(HttpMethod.Post,
+            $"{_auth.BaseUrl}/sell/inventory/v1/location/home", token);
+        req.Content = new StringContent(
+            JsonConvert.SerializeObject(body), Encoding.UTF8, "application/json");
+
+        var res  = await _http.SendAsync(req);
+        var json = await res.Content.ReadAsStringAsync();
+
+        if (!res.IsSuccessStatusCode)
+            throw new HttpRequestException(
+                $"Could not create merchant location ({(int)res.StatusCode}): {json}");
+    }
+
+    // ---- Inventory item ----
+
     private async Task CreateInventoryItemAsync(ListingDraft draft, List<string> imageUrls, string token)
     {
-        using var http = BuildClient(token);
-
-        var aspects = new Dictionary<string, List<string>>();
-
         var inventoryItem = new
         {
             availability = new
             {
-                shipToLocationAvailability = new
+                shipToLocationAvailability = new { quantity = draft.Quantity }
-                {
-                    quantity = draft.Quantity
-                }
             },
             condition = draft.ConditionId,
-            conditionDescription = draft.Condition == ItemCondition.Used ? "Used - see photos" : null,
+            conditionDescription = draft.Condition == ItemCondition.Used ? "Used — see photos" : null,
             description = draft.Description,
             title = draft.Title,
             product = new
@@ -75,7 +222,7 @@ public class EbayListingService
                 title       = draft.Title,
                 description = draft.Description,
                 imageUrls   = imageUrls.Count > 0 ? imageUrls : null,
-                aspects = aspects.Count > 0 ? aspects : null
+                aspects     = (object?)null
             }
         };
 
@@ -85,26 +232,22 @@ public class EbayListingService
         });
 
         var url = $"{_auth.BaseUrl}/sell/inventory/v1/inventory_item/{Uri.EscapeDataString(draft.Sku)}";
-        var request = new HttpRequestMessage(HttpMethod.Put, url)
+        using var req = MakeRequest(HttpMethod.Put, url, token);
-        {
+        req.Content = new StringContent(json, Encoding.UTF8, "application/json");
-            Content = new StringContent(json, Encoding.UTF8, "application/json")
+        req.Content.Headers.Add("Content-Language", "en-GB");
-        };
-        request.Content.Headers.Add("Content-Language", "en-GB");
 
-        var response = await http.SendAsync(request);
+        var res = await _http.SendAsync(req);
-        if (!response.IsSuccessStatusCode)
+        if (!res.IsSuccessStatusCode)
         {
-            var error = await response.Content.ReadAsStringAsync();
+            var err = await res.Content.ReadAsStringAsync();
-            throw new HttpRequestException($"Failed to create inventory item: {error}");
+            throw new HttpRequestException($"Failed to create inventory item: {err}");
         }
     }
 
+    // ---- Offer ----
+
     private async Task<string> CreateOfferAsync(ListingDraft draft, string token)
     {
-        using var http = BuildClient(token);
-
-        var listingPolicies = BuildListingPolicies(draft);
-
         var offer = new
         {
             sku                = draft.Sku,
@@ -113,12 +256,17 @@ public class EbayListingService
             availableQuantity  = draft.Quantity,
             categoryId         = draft.CategoryId,
             listingDescription = draft.Description,
-            listingPolicies,
+            listingPolicies    = new
+            {
+                fulfillmentPolicyId = _fulfillmentPolicyId,
+                paymentPolicyId     = _paymentPolicyId,
+                returnPolicyId      = _returnPolicyId
+            },
             pricingSummary = new
             {
                 price = new { value = draft.Price.ToString("F2"), currency = "GBP" }
             },
-            merchantLocationKey = "home",
+            merchantLocationKey = _merchantLocationKey,
             tax = new { vatPercentage = 0, applyTax = false }
         };
 
@@ -127,39 +275,45 @@ public class EbayListingService
             NullValueHandling = NullValueHandling.Ignore
         });
 
-        var url = $"{_auth.BaseUrl}/sell/inventory/v1/offer";
+        using var req = MakeRequest(HttpMethod.Post,
-        var response = await http.PostAsync(url, new StringContent(json, Encoding.UTF8, "application/json"));
+            $"{_auth.BaseUrl}/sell/inventory/v1/offer", token);
-        var responseJson = await response.Content.ReadAsStringAsync();
+        req.Content = new StringContent(json, Encoding.UTF8, "application/json");
 
-        if (!response.IsSuccessStatusCode)
+        var res         = await _http.SendAsync(req);
+        var responseJson = await res.Content.ReadAsStringAsync();
+
+        if (!res.IsSuccessStatusCode)
             throw new HttpRequestException($"Failed to create offer: {responseJson}");
 
-        var obj = JObject.Parse(responseJson);
+        return JObject.Parse(responseJson)["offerId"]?.ToString()
-        return obj["offerId"]?.ToString()
                ?? throw new InvalidOperationException("No offerId in create offer response.");
     }
 
+    // ---- Publish ----
+
     private async Task<string> PublishOfferAsync(string offerId, string token)
     {
-        using var http = BuildClient(token);
+        using var req = MakeRequest(HttpMethod.Post,
-        var url = $"{_auth.BaseUrl}/sell/inventory/v1/offer/{offerId}/publish";
+            $"{_auth.BaseUrl}/sell/inventory/v1/offer/{offerId}/publish", token);
-        var response = await http.PostAsync(url, new StringContent("{}", Encoding.UTF8, "application/json"));
+        req.Content = new StringContent("{}", Encoding.UTF8, "application/json");
-        var responseJson = await response.Content.ReadAsStringAsync();
 
-        if (!response.IsSuccessStatusCode)
+        var res          = await _http.SendAsync(req);
+        var responseJson = await res.Content.ReadAsStringAsync();
+
+        if (!res.IsSuccessStatusCode)
             throw new HttpRequestException($"Failed to publish offer: {responseJson}");
 
-        var obj = JObject.Parse(responseJson);
+        return JObject.Parse(responseJson)["listingId"]?.ToString()
-        return obj["listingId"]?.ToString()
                ?? throw new InvalidOperationException("No listingId in publish response.");
     }
 
+    // ---- Photo upload ----
+
     private async Task<List<string>> UploadPhotosAsync(List<string> photoPaths, string token)
     {
         var urls = new List<string>();
         if (photoPaths.Count == 0) return urls;
 
-        // Use Trading API UploadSiteHostedPictures for each photo
         var tradingBase = _auth.BaseUrl.Contains("sandbox")
             ? "https://api.sandbox.ebay.com/ws/api.dll"
             : "https://api.ebay.com/ws/api.dll";
@@ -167,7 +321,6 @@ public class EbayListingService
         foreach (var path in photoPaths.Take(12))
         {
             if (!File.Exists(path)) continue;
-
             try
             {
                 var url = await UploadSinglePhotoAsync(path, tradingBase, token);
@@ -176,7 +329,7 @@ public class EbayListingService
             }
             catch
             {
-                // Skip failed photo uploads, don't abort the whole listing
+                // Skip failed photos; don't abort the whole listing
             }
         }
 
@@ -186,8 +339,7 @@ public class EbayListingService
     private async Task<string?> UploadSinglePhotoAsync(string filePath, string tradingUrl, string token)
     {
         var fileBytes = await File.ReadAllBytesAsync(filePath);
-        var base64 = Convert.ToBase64String(fileBytes);
+        var ext       = Path.GetExtension(filePath).TrimStart('.').ToLower();
-        var ext = Path.GetExtension(filePath).TrimStart('.').ToUpper();
 
         var soapBody = $"""
             <?xml version="1.0" encoding="utf-8"?>
@@ -197,78 +349,39 @@ public class EbayListingService
               </RequesterCredentials>
               <PictureName>{Path.GetFileNameWithoutExtension(filePath)}</PictureName>
               <PictureSet>Supersize</PictureSet>
-              <ExternalPictureURL>https://example.com/placeholder.jpg</ExternalPictureURL>
             </UploadSiteHostedPicturesRequest>
             """;
 
-        // For binary upload, use multipart
+        // Use HttpRequestMessage with _photoHttp so we don't create a new socket per photo
-        using var http = new HttpClient();
-        http.DefaultRequestHeaders.Add("X-EBAY-API-SITEID", "3");
-        http.DefaultRequestHeaders.Add("X-EBAY-API-COMPATIBILITY-LEVEL", "967");
-        http.DefaultRequestHeaders.Add("X-EBAY-API-CALL-NAME", "UploadSiteHostedPictures");
-        http.DefaultRequestHeaders.Add("X-EBAY-API-IAF-TOKEN", token);
-
         using var content = new MultipartFormDataContent();
         content.Add(new StringContent(soapBody, Encoding.UTF8, "text/xml"), "XML Payload");
         var imageContent = new ByteArrayContent(fileBytes);
-        imageContent.Headers.ContentType = new MediaTypeHeaderValue($"image/{ext.ToLower()}");
+        imageContent.Headers.ContentType = new MediaTypeHeaderValue($"image/{ext}");
-        content.Add(imageContent, "dummy", Path.GetFileName(filePath));
+        content.Add(imageContent, "image", Path.GetFileName(filePath));
 
-        var response = await http.PostAsync(tradingUrl, content);
+        using var req = new HttpRequestMessage(HttpMethod.Post, tradingUrl);
+        req.Headers.Add("X-EBAY-API-SITEID",              "3");   // UK site
+        req.Headers.Add("X-EBAY-API-COMPATIBILITY-LEVEL", "967");
+        req.Headers.Add("X-EBAY-API-CALL-NAME",           "UploadSiteHostedPictures");
+        req.Headers.Add("X-EBAY-API-IAF-TOKEN",           token);
+        req.Content = content;
+
+        var response    = await _photoHttp.SendAsync(req);
         var responseXml = await response.Content.ReadAsStringAsync();
 
-        // Parse URL from XML response
         var match = System.Text.RegularExpressions.Regex.Match(
             responseXml, @"<FullURL>(.*?)</FullURL>");
         return match.Success ? match.Groups[1].Value : null;
     }
 
-    private JObject BuildListingPolicies(ListingDraft draft)
+    // ---- Helpers ----
-    {
-        var (serviceCode, costValue) = draft.Postage switch
-        {
-            PostageOption.RoyalMailFirstClass  => ("UK_RoyalMailFirstClass",  "1.50"),
-            PostageOption.RoyalMailSecondClass => ("UK_RoyalMailSecondClass", "1.20"),
-            PostageOption.RoyalMailTracked24   => ("UK_RoyalMailTracked24",   "2.95"),
-            PostageOption.RoyalMailTracked48   => ("UK_RoyalMailTracked48",   "2.50"),
-            PostageOption.FreePostage          => ("UK_RoyalMailSecondClass", "0.00"),
-            _                                  => ("UK_CollectionInPerson",   "0.00")
-        };
 
-        return new JObject
+    /// <summary>Creates a pre-authorised request targeting the eBay REST APIs.</summary>
+    private HttpRequestMessage MakeRequest(HttpMethod method, string url, string token)
     {
-            ["shippingPolicyName"] = "Default",
+        var req = new HttpRequestMessage(method, url);
-            ["paymentPolicyName"]  = "Default",
+        req.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
-            ["returnPolicyName"]   = "Default",
+        req.Headers.Add("X-EBAY-C-MARKETPLACE-ID", "EBAY_GB");
-            ["shippingCostType"]   = "FLAT_RATE",
+        return req;
-            ["shippingOptions"] = new JArray
-            {
-                new JObject
-                {
-                    ["optionType"] = "DOMESTIC",
-                    ["costType"]   = "FLAT_RATE",
-                    ["shippingServices"] = new JArray
-                    {
-                        new JObject
-                        {
-                            ["shippingServiceCode"] = serviceCode,
-                            ["shippingCost"] = new JObject
-                            {
-                                ["value"]    = costValue,
-                                ["currency"] = "GBP"
-                            }
-                        }
-                    }
-                }
-            }
-        };
-    }
-
-    private HttpClient BuildClient(string token)
-    {
-        var http = new HttpClient();
-        http.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
-        http.DefaultRequestHeaders.Add("X-EBAY-C-MARKETPLACE-ID", "EBAY_GB");
-        return http;
     }
 }

EbayListingTool/Views/MainWindow.xaml.cs

@@ -69,6 +69,7 @@ public partial class MainWindow : MetroWindow
     private void DisconnectBtn_Click(object sender, RoutedEventArgs e)
     {
         _auth.Disconnect();
+        _listingService.ClearCache(); // clear cached policy/location IDs for next login
         UpdateConnectionState();
         SetStatus("Disconnected from eBay.");
     }