Cloning entity that has a file uploaded

[talhacetin01]

I'm struggling about cloning an entity that has a file uploaded. When I try to clone it and save it, this error occurs:
System.InvalidOperationException: 'For security reasons, only temporary files can be used in uploads!'

In my entity dialog, i'm handling clone entity like this:

protected getCloningEntity() {
    var clone = super.getCloningEntity();

    if (clone.FilePath) {
        SummaryService.CopyToTemporary({ FilePath: clone.FilePath }, response => {
            clone.FilePath = response.TemporaryFilePath;
            this.form.FilePath.set_value({ Filename: response.TemporaryFilePath, OriginalName: '' });
        }, {
            blockUI: true,
            onError: e => notifyError("Kopyalama hatasi: \n" + (e?.Message || e))
        }
        )
    }
    return clone;
}

In my endpoint, i implemented CopyToTemporary like this:

public CopyAttachmentTemporaryResponse CopyToTemporary(
        [FromServices] IUploadStorage storage,
        [FromBody] CopyAttachmentTemporaryRequest request)
{
    var code = TemporaryFileHelper.RandomFileCode();
    var ext = Path.GetExtension(request.FilePath);
    var tempDir = $"temporary/{code}";
    var tempPath = $"{tempDir}/{code}{ext}";

    storage.WriteFile($"{tempDir}/{TemporaryFileHelper.DefaultTemporaryCheckFile}", new MemoryStream(new byte[0]), OverwriteOption.Overwrite);

    storage.CopyFrom(storage, request.FilePath, tempPath, OverwriteOption.AutoRename);

    return new CopyAttachmentTemporaryResponse
    {
        TemporaryFilePath = tempPath
    };
}

Also, I am new to this framework, so please help with code examples :)