In Asp.Net Core, how can I get the multipart/form-data from the body?

user_495247 0
Viewed 10433

In Asp.Net Core, it appears that they have done away with the Request.Content.ReadAsMultipartAsync functionality in favor of the IFormFile.

This makes uploading where you have an actual file a LOT easier, however, I have a use case where I need to upload a file to browser memory, process it, then send it as part of the multi-form data in the body. IFormFile cannot see this as there is no actual file to read. It only works if you have a filename property on the Content-Disposition and an actual file on the client to upload.

In my Asp.Net 4 app, I could read the mutlipart data in the body whether that was sent between boundaries or as an attached file.

How do I accomplish this in .Net Core?

asp.net-core multipartform-data
2 Answers

What I figured out is that the multipart values are passed into the HttpRequest.Form as an array of key/value pairs. The "name" value on the body's multipart determines the name of the key.

I created a helper method that grabs both files and form values.

public static List<FileModel> GetFileModelsFromRequest(HttpRequest request)
{
    var fileModels = new FileModels();

    foreach (var formField in request.Form)
    {
        // Form data 
        var fileModelText = formField.Value;

        ... process and add to the FileModel list
    }

    if (request.Form.Files != null && request.Form.Files.Count > 0)
    {
        foreach (var file in request.Form.Files)
        {
            using (MemoryStream ms = new MemoryStream())
            {
                // File data
                formFile.CopyTo(ms);                    
            }

            ... process and add to the FileModel list
        }
    }

    return fileModels;
}
user_4952470

I have done it this way. when I had to capture image from webcam and process (show that image in browser) it in browser memory and later on post that image using a form.

public IActionResult Index()
{
    var files = HttpContext.Request.Form.Files;

    if (files != null)
    {
        foreach (var file in files)
        {
            var fileName = file.Name;
        }
    }

    return View();
}

I used a JS library Webcam.js to capture image from webcam and show that image on the same page. and once a user is satisfied with the image, s/he can upload the image to the server.

<!-- Configure settings and attach camera -->  
<script language="JavaScript">  
    Webcam.set({  
        width: 320,  
        height: 240,  
        image_format: 'jpeg',  
        jpeg_quality: 90  
    });  
    Webcam.attach('#camera');  
</script>  
<!-- handle snapshot and displaying it locally -->  
<script language="JavaScript">  
    function take_snapshot() {  
        // take snapshot and get image data  
        Webcam.snap(function (data_uri) {  
            // display results in page  
            document.getElementById('imageResults').innerHTML =  
                '<img src="' +  
                data_uri +  
                '"/>';  

            Webcam.upload(data_uri,  
                '/Default/Index',  
                function (code, text) {  
                    console.log('Photo Captured');  
                });    
        });  
    }  
</script> 

<div class="panel panel-default">  
        <div class="panel-heading">Camera</div>  
        <div class="panel-body">  
            <div id="camera"></div>  
            <!-- A button for taking snaps -->  
            <form>  
                <input type="button" class="btn btn-success" value="Take Snapshot" onClick="take_snapshot()">  
            </form>  



 <div class="panel panel-default">  
        <div class="panel-heading">Captured Image</div>  
        <div class="panel-body">  
            <div id="imageResults">captured image will appear here...</div>  
        </div>  
        <br />  
        <br />  
    </div>

let me know if this is what you are looking for.

user_65663100
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