Once again pushing broken code

PcgsInvUi/Services/PcgsClient.cs

@@ -25,10 +25,34 @@ public class PcgsClient : ReactiveObject {
     private readonly string _apiKey;
     private int _numApiRequests;
 
-    public PcgsClient(string apiKey) {
+    /// <summary>
+    /// Creates a new instance of the PcgsClient class.
+    /// Although this is a constructor, it's meant to be called only from the CreateClient method.
+    /// </summary>
+    private PcgsClient(string apiKey) {
         _apiKey = apiKey;
             // "E8xivTVN_k4Q8ubk8Xv_uU11U91WX0wDht4S4m4BAf2HPmKnGrZ0J2f9nccM7Ns1VkGoT1SXYR74I7aNaMKqXlJGEy3oobseKV0nGiqu1IKvFkOTVjhV37SWUVExSDFMC6FLzs7xJQIHwkcxr5JFOQNmc4ZytEh_-hmCN3NL-z0fEk98tzBmPJ_F7bq_xNru86QMD2A9yalu_dWe-lCysfyE2bCA2EDqwvWenRYf-0XnNtp6qlxxCMlCd-TDqqRKLC3qefCwpXSemwBiNSP5gbC9pwcKrZugkruuJ0nyxxThZymm";
     }
+    
+    /// <summary>
+    /// Creates a new instance of the PcgsClient class.
+    /// </summary>
+    /// <param name="apiKey">The api key to use for requests.</param>
+    /// <returns>A new instance of the PcgsClient class, or null if the key is invalid.</returns>
+    public static PcgsClient? CreateClient(string apiKey) {
+        // Check if the api key is valid.
+        var testClient = new PcgsClient(apiKey);
+        if (!testClient.VerifyCredentials()) return null;
+        return testClient;
+    }
+
+    public bool VerifyCredentials() {
+        // Create a way to check if the api key given is valid
+        // I think the best way to do this is to make a request to the api and see if it returns the expected response.
+        var result = this.GetCoinFactsByGrade(1, "1");  // This is a known invalid coin id - this is because the api is very fast with invalid requests.
+        if (result.Result.Item1 == ErrorType.ApiKeyInvalid) return false;
+        return true;
+    }
 
     public async Task<(ErrorType, Coin?)> GetCoinFactsByGrade(int pcgsNumber, string grade, bool plusGrade = false) {
         using (HttpClient client = new HttpClient()) {