feat: implement listing a page of files

src/AnthropicClient/AnthropicApiClient.cs

@@ -388,6 +388,15 @@ public class AnthropicApiClient : IAnthropicApiClient
     return await CreateResultAsync<AnthropicFile>(response);
   }
 
+  /// <inheritdoc/>
+  public async Task<AnthropicResult<Page<AnthropicFile>>> ListFilesAsync(PagingRequest? request = null, CancellationToken cancellationToken = default)
+  {
+    var pagingRequest = request ?? new PagingRequest();
+    var endpoint = $"{FilesEndpoint}?{pagingRequest.ToQueryParameters()}";
+    var response = await SendRequestAsync(endpoint, cancellationToken: cancellationToken);
+    return await CreateResultAsync<Page<AnthropicFile>>(response);
+  }
+
   private async IAsyncEnumerable<AnthropicResult<Page<T>>> GetAllPagesAsync<T>(string endpoint, int limit = 20, [EnumeratorCancellation] CancellationToken cancellationToken = default)
   {
     var pagingRequest = new PagingRequest(limit: limit);

src/AnthropicClient/IAnthropicApiClient.cs

@@ -119,4 +119,12 @@ public interface IAnthropicApiClient
   /// <param name="cancellationToken">A token to cancel the asynchronous operation.</param>
   /// <returns>A task that represents the asynchronous operation. The task result contains the response as an <see cref="AnthropicResult{T}"/> where T is <see cref="AnthropicFile"/>.</returns>
   Task<AnthropicResult<AnthropicFile>> CreateFileAsync(CreateFileRequest request, CancellationToken cancellationToken = default);
+
+  /// <summary>
+  /// Lists files asynchronously, returning a single page of results.
+  /// </summary>
+  /// <param name="request">The paging request to use for listing the files.</param>
+  /// <param name="cancellationToken">A token to cancel the asynchronous operation.</param>
+  /// <returns>A task that represents the asynchronous operation. The task result contains the response as an <see cref="AnthropicResult{T}"/> where T is <see cref="Page{T}"/> where T is <see cref="AnthropicFile"/>.</returns>
+  Task<AnthropicResult<Page<AnthropicFile>>> ListFilesAsync(PagingRequest? request = null, CancellationToken cancellationToken = default);
 }

tests/AnthropicClient.Tests/EndToEnd/AnthropicApiClientTests.cs

@@ -708,4 +708,22 @@ public class AnthropicApiClientTests(ConfigurationFixture configFixture) : EndTo
     result.Value.Name.Should().Be(fileName);
     result.Value.MimeType.Should().Be(fileType);
   }
+
+  [Fact]
+  public async Task ListFilesAsync_WhenCalled_ItShouldReturnPageOfFiles()
+  {
+    var httpClient = new HttpClient();
+    httpClient.DefaultRequestHeaders.Add("anthropic-beta", "files-api-2025-04-14");
+    var client = CreateClient(httpClient);
+
+    var fileBytes = await File.ReadAllBytesAsync(TestFileHelper.GetTestFilePath("story.txt"));
+    var createFileRequest = new CreateFileRequest(fileBytes, "story.txt", "text/plain");
+    var createdFile = await client.CreateFileAsync(createFileRequest);
+
+    var result = await client.ListFilesAsync();
+
+    result.IsSuccess.Should().BeTrue();
+    result.Value.Should().BeOfType<Page<AnthropicFile>>();
+    result.Value.Data.Should().ContainSingle(f => f.Id == createdFile.Value.Id);
+  }
 }

tests/AnthropicClient.Tests/Integration/AnthropicApiClientTests.cs

@@ -1965,4 +1965,107 @@ public class AnthropicApiClientTests : IntegrationTest
       Type = "file"
     });
   }
+
+  [Fact]
+  public async Task ListFilesAsync_WhenCalled_ItShouldReturnPageOfFiles()
+  {
+    _mockHttpMessageHandler
+      .WhenListFilesRequest()
+      .Respond(
+        HttpStatusCode.OK,
+        "application/json",
+        @"{
+            ""data"": [
+              {
+                ""created_at"": ""2023-11-07T05:31:56Z"",
+                ""downloadable"": false,
+                ""filename"": ""example.txt"",
+                ""id"": ""file_013Zva2CMHLNnXjNJJKqJ2EF"",
+                ""mime_type"": ""text/plain"",
+                ""size_bytes"": 1234,
+                ""type"": ""file""
+              }
+            ],
+            ""has_more"": true,
+            ""first_id"": ""1"",
+            ""last_id"": ""1""
+          }"
+      );
+
+    var result = await Client.ListFilesAsync();
+
+    result.IsSuccess.Should().BeTrue();
+    result.Value.Should().BeOfType<Page<AnthropicFile>>();
+    result.Value.HasMore.Should().BeTrue();
+    result.Value.FirstId.Should().Be("1");
+    result.Value.LastId.Should().Be("1");
+    result.Value.Data.Should().BeEquivalentTo(new AnthropicFile[]
+    {
+      new()
+      {
+        CreatedAt = DateTimeOffset.Parse("2023-11-07T05:31:56Z"),
+        Downloadable = false,
+        Name = "example.txt",
+        Id = "file_013Zva2CMHLNnXjNJJKqJ2EF",
+        MimeType = "text/plain",
+        Size = 1234,
+        Type = "file"
+      }
+    });
+  }
+
+  [Fact]
+  public async Task ListFilesAsync_WhenCalledWithPagingRequest_ItShouldReturnPageOfFiles()
+  {
+    var pagingRequest = new PagingRequest(afterId: "next_id", limit: 10);
+
+    _mockHttpMessageHandler
+      .WhenListFilesRequest()
+      .WithQueryString(new Dictionary<string, string>
+      {
+        { "after_id", pagingRequest.AfterId },
+        { "limit", pagingRequest.Limit.ToString() },
+      })
+      .Respond(
+        HttpStatusCode.OK,
+        "application/json",
+        @"{
+            ""data"": [
+              {
+                ""created_at"": ""2023-11-07T05:31:56Z"",
+                ""downloadable"": false,
+                ""filename"": ""example.txt"",
+                ""id"": ""file_013Zva2CMHLNnXjNJJKqJ2EF"",
+                ""mime_type"": ""text/plain"",
+                ""size_bytes"": 1234,
+                ""type"": ""file""
+              }
+            ],
+            ""has_more"": true,
+            ""first_id"": ""1"",
+            ""last_id"": ""1""
+          }"
+      );
+
+    var result = await Client.ListFilesAsync(pagingRequest);
+
+    result.IsSuccess.Should().BeTrue();
+    result.Value.Should().BeOfType<Page<AnthropicFile>>();
+    result.Value.HasMore.Should().BeTrue();
+    result.Value.FirstId.Should().Be("1");
+    result.Value.LastId.Should().Be("1");
+    result.Value.Data.Should().BeEquivalentTo(new AnthropicFile[]
+    {
+      new()
+      {
+        CreatedAt = DateTimeOffset.Parse("2023-11-07T05:31:56Z"),
+        Downloadable = false,
+        Name = "example.txt",
+        Id = "file_013Zva2CMHLNnXjNJJKqJ2EF",
+        MimeType = "text/plain",
+        Size = 1234,
+        Type = "file"
+      }
+    });
+  }
 }

tests/AnthropicClient.Tests/Integration/IntegrationTest.cs

@@ -110,4 +110,10 @@ public static class MockHttpMessageHandlerExtensions
     return mockHttpMessageHandler
       .SetupBaseRequest(HttpMethod.Post, FilesEndpoint);
   }
+
+  public static MockedRequest WhenListFilesRequest(this MockHttpMessageHandler mockHttpMessageHandler)
+  {
+    return mockHttpMessageHandler
+      .SetupBaseRequest(HttpMethod.Get, FilesEndpoint);
+  }
 }