Saving Files to SQL server using knockout js - file-upload

Question

I have a requirement on my web app to save multiple attachments to my SQL server. The attachments can be in any format. Is it possible to create a knockout viewmodel to encode the file type on client side to binary and transferring that binary info to my SQL server?
I currently have this method in my REST service:
[OperationContract, WebInvoke(ResponseFormat = WebMessageFormat.Json)]
public string PostAttachments (string FileName)
{
try
{
var MyAttachment = new Binary(File.ReadAllBytes(FileName));
return "Attachments Created";
}
catch (Exception ex)
{
return DefaultError + ex;
}
}
I know this is incorrect but I am really not sure how to do this file upload. I believe I am over complicating it. Any Assistance would be greatly appreciated.

Answer 1

You will have to transfer the buffer to the server not just the filename, since the file exists on the client.
I used the HTML5 FileReader in my last KO project
First a custom binding to read the file from the DOM element
(function () {
ko.bindingHandlers.file = {
init: function (element, valueAccessor, allBindingsAccessor) {
ko.utils.registerEventHandler(element, "change", function () {
writeValueToProperty(valueAccessor(), allBindingsAccessor, "file", element.files[0]);
});
},
update: function (element, valueAccessor) {
if (ko.utils.unwrapObservable(valueAccessor()) == null) {
element.value = "";
}
}
};
var writeValueToProperty = function (property, allBindingsAccessor, key, value, checkIfDifferent) {
if (!property || !ko.isObservable(property)) {
var propWriters = allBindingsAccessor()['_ko_property_writers'];
if (propWriters && propWriters[key])
propWriters[key](value);
} else if (ko.isWriteableObservable(property) && (!checkIfDifferent || property.peek() !== value)) {
property(value);
}
};
} ());
FileReader usage (code specific for how I used it in my app). Check the FileReader part only.
Note if you have large files you need to stream instead
processFiles: function (viewModel, callback) {
var files = [];
ko.utils.arrayForEach(viewModel.files, function (file) {
if (file.fileUpload() == null) return;
var count = Enumerable.From(viewModel.files)
.Where(function(f) { return f.fileUpload() != null; })
.Count();
var reader = new FileReader();
reader.onload = function (e) {
var base64 = e.target.result.substr(e.target.result.indexOf(",") + 1);
files.push({ Type: file.type, Data: base64, Filename: file.fileUpload().name });
if (files.length == count) {
callback(files);
}
};
reader.readAsDataURL(file.fileUpload());
});
}
Update
Like said this is code for my use case, you will need to change it to fit your purpose
<div data-bind="foreach: files">
<p><label data-bind="text: typeName"></label><input data-bind="file: fileUpload" type="file" /></p>
</div>
Controller (I would use WebApi if I did this today)
public JsonResult UploadFiles(IEnumerable<FileUploadViewModel> uploads)
{
fileRepository.SaveUploadedFiles(Mapper.Map<IEnumerable<FileUploadViewModel>, IEnumerable <FileUpload>> (uploads));
return string.Empty.AsJson();
}
FileUploadViewModel
public class FileUploadViewModel
{
public FileType Type { get; set; }
public string Filename { get; set; }
public string Data { get; set; }
}
Automapper config
Mapper.CreateMap<FileUploadViewModel, FileUpload>()
.ForMember(to => to.Buffer, opt => opt.MapFrom(from => Convert.FromBase64String(from.Data)));