title: Dropzone with ModelBinding select box Not Posting
body: <p>I am trying to upload files with Dropzone.js to an azure blob. I also need to have the data from the vendor selector in the Post  to upload files to the right blob container.  Once I add files to the dropzone I get a 400 error and I dont hit the OnPost Method in the cs page. I need both the files and the selector form.</p>
  <p>HTML Page</p>
  <pre><code>@model SipiARPortal.Pages.SystemAdmin.AdminFileUploadModel
  @inject IVendor _vendor
  @inject IAzureBlob _blob
  @{
      ViewData[&quot;Title&quot;] = &quot;Admin File Upload&quot;;
      ViewData[&quot;Header&quot;] = new PageHeader()
      {
          Title = &quot;ADMIN FILE UPLOAD&quot;,
          SubTitle = &quot;Upload Files here&quot;,
          Breadcrumbs = new List&lt;Breadcrumb&gt;() {
              new Breadcrumb() { Name = &quot;Admin File Uplaod&quot;, URL = &quot;/systemadmin/adminfileupload&quot; }
          }
      };
  }
  &lt;link href=&quot;~/css/dropzone.css&quot; rel=&quot;stylesheet&quot; /&gt;
  &lt;div class=&quot;row clearfix&quot;&gt;
      &lt;div class=&quot;col-lg-12 col-md-12 col-sm-12&quot;&gt;
          &lt;div class=&quot;card&quot;&gt;
              &lt;div class=&quot;body&quot;&gt;
                  &lt;form action=&quot;~/systemadmin/adminfileupload&quot; method=&quot;post&quot;&gt;
                      &lt;div class=&quot;form-group form-float&quot;&gt;
  
                          &lt;select asp-for=&quot;SelVendor&quot; asp-items=&quot;Model.VendorOptions&quot;&gt;
                              &lt;option value=&quot;&quot;&gt;Choose a Vendor&lt;/option&gt;
                          &lt;/select&gt;
  
                      &lt;/div&gt;
                      &lt;div class=&quot;form-group form-float&quot;&gt;
  
                          &lt;input class=&quot;dropzone&quot; enctype=&quot;multipart/form-data&quot;
                                 id=&quot;my-dropzone&quot;&gt;
                          @Html.AntiForgeryToken()
                          &lt;/input&gt;
  
                      &lt;/div&gt;
                  &lt;/form&gt;
              &lt;/div&gt;
          &lt;/div&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  
  &lt;div id=&quot;SuccessGrid&quot;&gt;&lt;/div&gt;
  &lt;div id=&quot;FailedGrid&quot;&gt;&lt;/div&gt;
  @section Scripts {
      &lt;script src=&quot;~/lib/dropzone/dropzone.js&quot;&gt;&lt;/script&gt;
      &lt;script type=&quot;text/javascript&quot;&gt;
          var gridObj = null;
          Dropzone.options.myDropzone = {
              paramName: &quot;file&quot;,
              acceptedFiles: 'application/pdf',
              dictDefaultMessage: 'Drop results .pdf or .zip files here for verification',
              url: '/systemadmin/adminfileupload'
          }
  
      &lt;/script&gt;
  }
  </code></pre>
  <p>.CS page</p>
  <pre><code>public class AdminFileUploadModel : PageModel
      {
          private readonly ILogger&lt;AdminFileUploadModel&gt; _logger;
          private readonly UserManager&lt;ApplicationUser&gt; _userManager;
          public readonly IAzureBlob _blob;
          private readonly IVendor _vendor;
          private readonly ApplicationDbContext _db;
          private readonly ConfigurationDbContext _cdb;
  
          [BindProperty]
          public IFormFile UploadFiles { get; set; }
          [BindProperty]
          public string SelVendor { get; set; }
          public SelectList VendorOptions { get; set; }
          public List&lt;VendorList&gt; Vendors { get; set; }
  
          public AdminFileUploadModel(IAzureBlob blob, ApplicationDbContext db, ILogger&lt;AdminFileUploadModel&gt; logger, ConfigurationDbContext cdb, IVendor vendor) 
          {
              _blob = blob;
              _logger = logger;
              _vendor = vendor;
              _db = db;
              _cdb = cdb;
          }
          public IActionResult OnGet()
          {
              Vendors = _db.Vendors.Where(x =&gt; x.Active == true).Select(x =&gt; new VendorList { VendorId = x.VendorId, Name = x.Name }).ToList();
              VendorOptions = new SelectList(Vendors, &quot;VendorId&quot;, &quot;Name&quot;);
              return Page();
          }
          public async Task&lt;IActionResult&gt; OnPostAsync(IFormFile file)
          {
              
              ServiceResult&lt;List&lt;ResultIssue&gt;&gt; retVal = new ServiceResult&lt;List&lt;ResultIssue&gt;&gt;() { Data = new List&lt;ResultIssue&gt;(), Success = true };
           
              try
              {
                  if (SelVendor != null )
                  {
                       
                      await _blob.SaveFileStream(file.OpenReadStream(), &quot;pending&quot;, file.FileName);
                      retVal.Message = &quot;Files have been uploaded.&quot;;
                      retVal.Success = true;
                  }
                  else 
                  {
                      retVal.Message = &quot;Must select a Vendor&quot;;
                      retVal.Success = false;
                  }
                  //var blobStream = await _blob.GetFileStream(blob, sigFileName);
              }
              catch (Exception ex)
              {
                  _logger.LogError(ex, &quot;File Upload&quot;);
                  retVal.Message = &quot;Error parsing results file - did you select the correct format?&quot;;
                  retVal.Success = false;
              }
              return new JsonResult(retVal);
          }
  
  
      }
  </code></pre>