Pass array object inside formdata

If you post data by ajax,you need firstly know the two things below:

1.For each property of the complex type, model binding looks through the sources for the name pattern prefix.property_name. If nothing is found, it looks for just property_name without the prefix.For model you receive in backend is a List,you need give the name like:[index].FormFile or model[index].FormFile.

2.Your model has a IFormFile and your action receives a list model,if you only pass the IFormFile you need remove FromForm attribute and be sure do not have [ApiController].It is a known github issue and this has been moved to Next sprint planning milestone.

Here is a whole working demo:

Model:

public class FileModels
{
    public string Description { get; set; }

    public IFormFile FormFile { get; set; }
}

View:

<input type="file" multiple onchange="saveDocuments(this.files)"/>
<div class="form-group">
    <input type="button" value="Submit" id="submit" class="btn btn-primary" />
</div>

@section Scripts
{
    <script>
        function saveDocuments(documentList) {
            if (documentList.length > 0) {
                var form = new FormData();
                for (var i = 0; i < documentList.length; i++) {                    
                    var file = documentList[i];                    
                    form.append('model['+i+'].FormFile', file);
                }
                savePhysicalFile(form);
            }
        }    
        function savePhysicalFile(formData) {
            if (formData != null) {
                $.ajax({
                    url: "/Home/Save",
                    type: 'POST',
                    dataType: "json",
                    contentType: "multipart/form-data",
                    data: formData,
                    processData: false,
                    contentType: false,
                    success: function (result) {
                        console.log("Success", result);
                    },
                    error: function (data) {
                        console.log(data);
                    }
                });
            }
        }
    </script>
}

Controller:

[HttpPost]
public void Save(List<FileModels> model)
{
    //...
}

Result:

If you post data by form submit,here is a whole working demo:

@model FileModels
<form asp-action="Save" method="post" enctype="multipart/form-data">
    @for (int i = 0; i < 3; i++)
    {
        <div>
            <input type="text" asp-for="Description" name="[@i].Description" />
        </div>
        <div>
            <input type="file" asp-for="FormFile" name="[@i].FormFile" />
        </div>
       
    }
    <div class="form-group">
        <input type="submit" value="Submit" id="submit" class="btn btn-primary" />
    </div>
</form>

Controller:

[HttpPost]
public void Save(List<FileModels> model)
{
    //...
}

Result2: