Setting the form boundary for #1716

Author: alexeyzimarev

src/RestSharp/Request/HttpContentExtensions.cs

@@ -44,11 +44,6 @@ public HttpContent BuildContent() {
         var postParameters = _request.Parameters.GetContentParameters(_request.Method);
         AddBody(!postParameters.IsEmpty());
         AddPostParameters(postParameters);
-
-        if (Content is MultipartFormDataContent && _request.FormatMultipartContentType != null) {
-            ReplaceHeader(ContentType, GetContentTypeHeader(Content.Headers.ContentType!.MediaType!));
-        }
-
         AddHeaders();
 
         return Content!;
@@ -57,7 +52,7 @@ public HttpContent BuildContent() {
     void AddFiles() {
         if (!_request.HasFiles() && !_request.AlwaysMultipartFormData) return;
 
-        var mpContent = new MultipartFormDataContent();
+        var mpContent = new MultipartFormDataContent(GetOrSetFormBoundary());
 
         foreach (var file in _request.Files) {
             var stream = file.GetFile();
@@ -122,6 +117,8 @@ static bool BodyShouldBeMultipartForm(BodyParameter bodyParameter) {
         return bodyParameter.Name.IsNotEmpty() && bodyParameter.Name != bodyContentType;
     }
 
+    string GetOrSetFormBoundary() => _request.FormBoundary ?? (_request.FormBoundary = Guid.NewGuid().ToString());
+
     void AddBody(bool hasPostParameters) {
         if (!_request.TryGetBodyParameter(out var bodyParameter)) return;
 
@@ -130,7 +127,7 @@ void AddBody(bool hasPostParameters) {
         // we need to send the body
         if (hasPostParameters || _request.HasFiles() || BodyShouldBeMultipartForm(bodyParameter!) || _request.AlwaysMultipartFormData) {
             // here we must use multipart form data
-            var mpContent = Content as MultipartFormDataContent ?? new MultipartFormDataContent();
+            var mpContent = Content as MultipartFormDataContent ?? new MultipartFormDataContent(GetOrSetFormBoundary());
             var ct        = bodyContent.Headers.ContentType?.MediaType;
             var name      = bodyParameter!.Name.IsEmpty() ? ct : bodyParameter.Name;
 
@@ -167,7 +164,7 @@ void AddPostParameters(ParametersCollection? postParameters) {
             var formContent = new FormUrlEncodedContent(
                 _request.Parameters
                     .Where(x => x.Type == ParameterType.GetOrPost)
-                    .Select(x => new KeyValuePair<string, string>(x.Name!, x.Value!.ToString()!))!
+                    .Select(x => new KeyValuePair<string, string>(x.Name!, x.Value!.ToString()!))
             );
             Content = formContent;
         }
@@ -195,23 +192,18 @@ void AddHeader(Parameter parameter) {
             var pName = Ensure.NotNull(parameter.Name, nameof(parameter.Name));
             ReplaceHeader(pName, value);
         }
+
+        string GetContentTypeHeader(string contentType)
+            => Content is MultipartFormDataContent
+                ? $"{contentType}; boundary=\"{GetOrSetFormBoundary()}\""
+                : contentType;
     }
 
     void ReplaceHeader(string name, string? value) {
         Content!.Headers.Remove(name);
         Content!.Headers.TryAddWithoutValidation(name, value);
     }
 
-    static readonly FormatContentTypeHeader DefaultContentTypeHeader = (contentType, boundary) => $"{contentType}; boundary=\"{boundary}\"";
-
-    string GetContentTypeHeader(string contentType) {
-        return Content is MultipartFormDataContent mpContent
-            ? ContentTypeValue()(contentType, mpContent.GetFormBoundary())
-            : contentType;
-
-        FormatContentTypeHeader ContentTypeValue() => _request.FormatMultipartContentType ?? DefaultContentTypeHeader;
-    }
-
     public void Dispose() {
         _streams.ForEach(x => x.Dispose());
         Content?.Dispose();

src/RestSharp/Request/RequestContent.cs

@@ -17,8 +17,6 @@
 
 namespace RestSharp;
 
-public delegate string FormatContentTypeHeader(string contentType, string formBoundary);
-
 /// <summary>
 /// Container for data used to make requests
 /// </summary>
@@ -69,6 +67,8 @@ public RestRequest(Uri resource, Method method = Method.Get)
     /// Always send a multipart/form-data request - even when no Files are present.
     /// </summary>
     public bool AlwaysMultipartFormData { get; set; }
+    
+    public string? FormBoundary { get; set; }
 
     /// <summary>
     /// Container of all HTTP parameters to be passed with the request.
@@ -147,11 +147,6 @@ public RestRequest(Uri resource, Method method = Method.Get)
     /// </summary>
     public HttpCompletionOption CompletionOption { get; set; } = HttpCompletionOption.ResponseContentRead;
 
-    /// <summary>
-    /// Function that formats the content type header for multipart form fata
-    /// </summary>
-    public FormatContentTypeHeader? FormatMultipartContentType { get; set; }
-
     /// <summary>
     /// Set this to write response to Stream rather than reading into memory.
     /// </summary>

src/RestSharp/Request/RestRequest.cs

@@ -84,16 +84,9 @@ public async Task MultipartFormData() {
 
         AddParameters(request);
 
-        string boundary = null;
-
-        request.OnBeforeRequest = http => {
-            boundary = ((MultipartFormDataContent)http.Content)!.GetFormBoundary();
-            return default;
-        };
-
         var response = await _client.ExecuteAsync(request);
 
-        var expected = string.Format(Expected, boundary);
+        var expected = string.Format(Expected, request.FormBoundary);
 
         _output.WriteLine($"Expected: {expected}");
         _output.WriteLine($"Actual: {response.Content}");
@@ -110,15 +103,10 @@ public async Task MultipartFormData_HasDefaultContentType() {
 
         request.AddParameter(new BodyParameter("controlName", "test", "application/json"));
 
-        string boundary = null;
-
-        request.OnBeforeRequest = http => {
-            boundary = ((MultipartFormDataContent)http.Content)!.GetFormBoundary();
-            return default;
-        };
-
         var response = await _client.ExecuteAsync(request);
 
+        var boundary = request.FormBoundary;
+
         var expectedFileAndBodyRequestContent   = string.Format(ExpectedFileAndBodyRequestContent, boundary);
         var expectedDefaultMultipartContentType = string.Format(ExpectedDefaultMultipartContentType, boundary);
 
@@ -140,14 +128,8 @@ public async Task MultipartFormData_WithCustomContentType() {
         request.AddFile("fileName", path);
         request.AddParameter(new BodyParameter("controlName", "test", "application/json"));
 
-        string boundary = null;
-
-        request.OnBeforeRequest = http => {
-            boundary = ((MultipartFormDataContent)http.Content)!.GetFormBoundary();
-            return default;
-        };
-
         var response = await _client.ExecuteAsync(request);
+        var boundary = request.FormBoundary;
 
         var expectedFileAndBodyRequestContent  = string.Format(ExpectedFileAndBodyRequestContent, boundary);
         var expectedCustomMultipartContentType = string.Format(ExpectedCustomMultipartContentType, boundary);
@@ -167,58 +149,23 @@ public async Task MultipartFormData_WithParameterAndFile_Async() {
 
         request.AddParameter(new BodyParameter("controlName", "test", "application/json"));
 
-        string boundary = null;
-
-        request.OnBeforeRequest = http => {
-            boundary = ((MultipartFormDataContent)http.Content)!.GetFormBoundary();
-            return default;
-        };
-
         var response = await _client.ExecuteAsync(request);
+        var boundary = request.FormBoundary;
 
         var expectedFileAndBodyRequestContent = string.Format(ExpectedFileAndBodyRequestContent, boundary);
 
         response.Content.Should().Be(expectedFileAndBodyRequestContent);
     }
 
-    [Fact]
-    public async Task MultipartFormDataWithBoundaryOverride() {
-        var request = new RestRequest("/", Method.Post) {
-            AlwaysMultipartFormData    = true,
-            FormatMultipartContentType = (ct, b) => $"{ct}; boundary=--------{b}"
-        };
-
-        AddParameters(request);
-
-        HttpContent content  = null;
-        var         boundary = "";
-
-        request.OnBeforeRequest = http => {
-            content  = http.Content;
-            boundary = ((MultipartFormDataContent)http.Content)!.GetFormBoundary();
-            return default;
-        };
-
-        await _client.ExecuteAsync(request);
-
-        var contentType = content.Headers.ContentType!.ToString();
-        contentType.Should().Be($"multipart/form-data; boundary=--------{boundary}");
-    }
-
     [Fact]
     public async Task MultipartFormDataAsync() {
         var request = new RestRequest("/", Method.Post) { AlwaysMultipartFormData = true };
 
         AddParameters(request);
 
-        string boundary = null;
-
-        request.OnBeforeRequest = http => {
-            boundary = ((MultipartFormDataContent)http.Content)!.GetFormBoundary();
-            return default;
-        };
-
         var response = await _client.ExecuteAsync(request);
+
+        var boundary = request.FormBoundary;
         var expected = string.Format(Expected, boundary);
 
         response.Content.Should().Be(expected);