如何将文件上传到 Web API 服务器并将参数发送到操作

抱歉答案晚了，但我们解决了问题（我忘了我没有在这里上传答案）。基本上，我们所做的是在临时位置调用 ReadAsMultiPartAsync 方法，然后从请求中提取其他参数。之后，我们验证了输入并将文件从临时位置移动到永久位置。

如果你想看代码，这就是对我们特定示例有效的代码，我相信适应任何工作案例场景都非常简单：

在客户端，我们有以下形式（是的，此实现用于演示目的，仅支持发送一个文件......此外，输入类型="文件"字段确实在表单之外;在我们的例子中，fileId 文本输入是手动完成的，仅用于测试目的）

<input type="file" name="data" id="fileInput" multiple="multiple" />
<form id="fileSubmission">            
    <input type="text" width="10" onchange="getFileDetails()" autocomplete="off" placeholder="FileId" name="files[0].Id" id="fileId" /> 
    <input type="hidden" name="files[0].FileName" id="FileName"/>
    <input type="hidden" name="files[0].Extension" id="Extension"/>
    <input type="hidden" name="files[0].EntityId" id="EntityId"/>
    <br /><br />
    <input type="submit" id="Upload" value="Upload" />
</form>

其中 getFileDetails（） 填充其他输入字段。此外，表单使用以下jQuery/Javascript发送到服务器：

$('#Upload').click(function(e) {
            e.preventDefault();
            var courseId = $('#courseId').val();
            var fileId = $('#fileId').val();
            if (!courseId || !fileId) {
                return;
            }
            var headers = new Array();
            headers["SessionId"] = sessionId;
            headers["contentType"] = "application/json; charset=UTF-8";
            var formData = new FormData();
            var opmlFile = $('#fileInput').get(0).files;
            // this is like the model we're expecting on the server
            var files = [];
            files.push({ 'Id': $('#fileId').val(), 'OriginalFileName': opmlFile[0].name, 'FileName': $('#FileName').val(), 'Extension': $('#Extension').val(), 'EntityId': $('#EntityId').val() });
            formData.append("fileModels", JSON.stringify(files));
            formData.append("File_0", opmlFile[0]);

            $.ajax({
                url: "api/Courses/" + courseId + "/Submissions/Add/",
                headers: headers,
                type: 'POST',
                data: formData,
                cache: false,
                contentType: false,
                processData: false,
                dataType: 'json'
            });
        });

在服务器端，我们有以下内容：

// POST: api/Courses/{courseId}/Submissions/Add
[HttpPost]
[ValidateModelState]
[ValidateMimeMultipartContent]
[PermissionsAuthorize(CoursePermissions.CanCreateSubmissions)]
public async Task<HttpResponseMessage> Add(int courseId)
    {
        // the same as in the jQuery part
        const string paramName = "fileModels";
        // Put the files in a temporary location
        // this way we call ReadAsMultiPartAsync and we get access to the other data submitted
        var tempPath = HttpContext.Current.Server.MapPath("~/App_Data/Temp/" + Guid.NewGuid());
        Directory.CreateDirectory(tempPath);
        var streamProvider = new MultipartFormDataStreamProvider(tempPath);
        var readResult = await Request.Content.ReadAsMultipartAsync(streamProvider);
        if (readResult.FormData[paramName] == null)
        {
            // We don't have the FileModels ... delete the TempFiles and return BadRequest
            Directory.Delete(tempPath, true);
            return Request.CreateResponse(HttpStatusCode.BadRequest);
        }
        // The files have been successfully saved in a TempLocation and the FileModels are not null
        // Validate that everything else is fine with this command
        var fileModels = JsonConvert.DeserializeObject<IEnumerable<FileModelExtension>>(readResult.FormData[paramName]).ToList();
        // AT THIS POINT, ON THE SERVER, WE HAVE ALL THE FILE MODELS 
        // AND ALL THE FILES ARE SAVED IN A TEMPORARY LOCATION
        // NEXT STEPS ARE VALIDATION OF THE INPUT AND THEN 
        // MOVING THE FILE FROM THE TEMP TO THE PERMANENT LOCATION
        // YOU CAN ACCESS THE INFO ABOUT THE FILES LIKE THIS:
        foreach (var tempFile in readResult.FileData)
            {
                var originalFileName = tempFile.Headers.ContentDisposition.FileName.Replace("'"", string.Empty);
                var localTempPath = tempFile.LocalFileName;
            }
    }

我希望这将帮助任何尝试使用 Post 请求一次向服务器提交文件和其他参数的人！ :)

注意：服务器上使用的某些属性是自定义的。PermissionAuthorize，ValidateModelState和ValidateMimeMultiPartContent是我们使用的自定义过滤器。后两者的实施受到 http://benfoster.io/blog/automatic-modelstate-validation-in-aspnet-mvc

multipartcontent 属性只是对 actionContext.Request.Content.IsMimeMultipartContent（） 进行检查，如下所示：

public class ValidateMimeMultipartContent : ActionFilterAttribute
{
    public override void OnActionExecuting(HttpActionContext actionContext)
    {
        if (!actionContext.Request.Content.IsMimeMultipartContent())
        {
            actionContext.Response = actionContext.Request.CreateErrorResponse(HttpStatusCode.UnsupportedMediaType, Messages.UnsupportedMediaType);
        }
    }
}