fix: use null instead of ` for default string` args

Author: ThirdEyeSqueegee

src/Amazon.SecretsManager.Extensions.Caching/ISecretsManagerCache.cs

@@ -39,7 +39,7 @@ public interface ISecretsManagerCache : IDisposable
         /// <param name="versionStage">The version stage.</param>
         /// <param name="cancellationToken">The cancellation token used for the Secrets Manager API call.</param>
         /// <returns>The <c>SecretBinary</c>.</returns>
-        Task<byte[]> GetSecretBinary(string secretId, string versionId = "", string versionStage = "", CancellationToken cancellationToken = default);
+        Task<byte[]> GetSecretBinary(string secretId, string versionId = null, string versionStage = null, CancellationToken cancellationToken = default);
 
         /// <summary>
         /// Asynchronously retrieves the specified <c>SecretString</c> after calling <see cref="GetCachedSecret"/>.
@@ -50,7 +50,7 @@ public interface ISecretsManagerCache : IDisposable
         /// <param name="versionStage">The version stage.</param>
         /// <param name="cancellationToken">The cancellation token used for the Secrets Manager API call.</param>
         /// <returns>The <c>SecretString</c>.</returns>
-        Task<string> GetSecretString(string secretId, string versionId = "", string versionStage = "", CancellationToken cancellationToken = default);
+        Task<string> GetSecretString(string secretId, string versionId = null, string versionStage = null, CancellationToken cancellationToken = default);
 
         /// <summary>
         /// Requests the secret value from SecretsManager asynchronously and updates the cache entry with any changes.

src/Amazon.SecretsManager.Extensions.Caching/SecretCacheItem.cs

@@ -46,7 +46,7 @@ protected override async Task<DescribeSecretResponse> ExecuteRefreshAsync(Cancel
         /// <summary>
         /// Asynchronously retrieves the GetSecretValueResponse from the proper SecretCacheVersion.
         /// </summary>
-        protected override async Task<GetSecretValueResponse> GetSecretValueAsync(DescribeSecretResponse result, string versionId = "", string versionStage = "", CancellationToken cancellationToken = default)
+        protected override async Task<GetSecretValueResponse> GetSecretValueAsync(DescribeSecretResponse result, string versionId = null, string versionStage = null, CancellationToken cancellationToken = default)
         {
             SecretCacheVersion version = GetVersion(result, versionId, versionStage);
             if (version == null)
@@ -75,19 +75,19 @@ public override bool Equals(object obj)
         /// Retrieves the SecretCacheVersion corresponding to the Version Stage
         /// specified by the SecretCacheConfiguration.
         /// </summary>
-        private SecretCacheVersion GetVersion(DescribeSecretResponse describeResult, string versionId = "", string versionStage = "")
+        private SecretCacheVersion GetVersion(DescribeSecretResponse describeResult, string versionId = null, string versionStage = null)
         {
             if (null == describeResult?.VersionIdsToStages) return null;
             String currentVersionId = null;
             foreach (KeyValuePair<String, List<String>> entry in describeResult.VersionIdsToStages)
             {
-                if (versionId != string.Empty && entry.Key.Equals(versionId))
+                if (versionId != null && entry.Key.Equals(versionId))
                 {
                     currentVersionId = versionId;
                     break;
                 }
 
-                if ((versionStage != string.Empty && entry.Value.Contains(versionStage)) || entry.Value.Contains(config.VersionStage))
+                if ((versionStage != null && entry.Value.Contains(versionStage)) || entry.Value.Contains(config.VersionStage))
                 {
                     currentVersionId = entry.Key;
                     break;

src/Amazon.SecretsManager.Extensions.Caching/SecretCacheObject.cs

@@ -96,7 +96,7 @@ public SecretCacheObject(String secretId, IAmazonSecretsManager client, SecretCa
 
         protected abstract Task<T> ExecuteRefreshAsync(CancellationToken cancellationToken = default);
 
-        protected abstract Task<GetSecretValueResponse> GetSecretValueAsync(T result, string versionId = "", string versionStage = "", CancellationToken cancellationToken = default);
+        protected abstract Task<GetSecretValueResponse> GetSecretValueAsync(T result, string versionId = null, string versionStage = null, CancellationToken cancellationToken = default);
 
         /// <summary>
         /// Return the typed result object.
@@ -209,7 +209,7 @@ public async Task<bool> RefreshNowAsync(CancellationToken cancellationToken = de
         /// If the secret is due for a refresh, the refresh will occur before the result is returned.
         /// If the refresh fails, the cached result is returned, or the cached exception is thrown.
         /// </summary>
-        public async Task<GetSecretValueResponse> GetSecretValue(CancellationToken cancellationToken, string versionId = "", string versionStage = "")
+        public async Task<GetSecretValueResponse> GetSecretValue(CancellationToken cancellationToken, string versionId = null, string versionStage = null)
         {
             bool success = false;
             await Lock.WaitAsync(cancellationToken);

src/Amazon.SecretsManager.Extensions.Caching/SecretCacheVersion.cs

@@ -56,7 +56,7 @@ protected override async Task<GetSecretValueResponse> ExecuteRefreshAsync(Cancel
             return await this.client.GetSecretValueAsync(new GetSecretValueRequest { SecretId = this.secretId, VersionId = this.versionId }, cancellationToken);
         }
 
-        protected override Task<GetSecretValueResponse> GetSecretValueAsync(GetSecretValueResponse result, string versionId = "", string versionStage = "", CancellationToken cancellationToken = default)
+        protected override Task<GetSecretValueResponse> GetSecretValueAsync(GetSecretValueResponse result, string versionId = null, string versionStage = null, CancellationToken cancellationToken = default)
         {
             return Task.FromResult(result);
         }

src/Amazon.SecretsManager.Extensions.Caching/SecretsManagerCache.cs

@@ -94,7 +94,7 @@ public void Dispose()
         /// <param name="versionStage">The version stage.</param>
         /// <param name="cancellationToken">The cancellation token used for the Secrets Manager API call.</param>
         /// <returns>The <c>SecretString</c>.</returns>
-        public async Task<String> GetSecretString(String secretId, string versionId = "", string versionStage = "", CancellationToken cancellationToken = default)
+        public async Task<String> GetSecretString(String secretId, string versionId = null, string versionStage = null, CancellationToken cancellationToken = default)
         {
             SecretCacheItem secret = GetCachedSecret(secretId);
             GetSecretValueResponse response = null;
@@ -111,7 +111,7 @@ public async Task<String> GetSecretString(String secretId, string versionId = ""
         /// <param name="versionStage">The version stage.</param>
         /// <param name="cancellationToken">The cancellation token used for the Secrets Manager API call.</param>
         /// <returns>The <c>SecretBinary</c>.</returns>
-        public async Task<byte[]> GetSecretBinary(String secretId, string versionId = "", string versionStage = "", CancellationToken cancellationToken = default)
+        public async Task<byte[]> GetSecretBinary(String secretId, string versionId = null, string versionStage = null, CancellationToken cancellationToken = default)
         {
             SecretCacheItem secret = GetCachedSecret(secretId);
             GetSecretValueResponse response = null;