How to get rid of exceed length of query string in my POST request?

Question

Use to send the base64 image to the server, and sometimes face the problem of exceeding the maximum line length. How it can be avoided?

Code of my POST:

 var values = new Dictionary<string, string>
       {
        { "kod", "111" },
        { "id_user", user.Id },
        { "image", encodedFile },
        { "title", "MyText" },
        { "text", "1234526" }
       };

        var content = new System.Net.Http.FormUrlEncodedContent(values);

        var response = await client.PostAsync("http://MyUri/tape.php", content);

        var responseString = await response.Content.ReadAsStringAsync();

---

Full code of my request:

private async void Send_File_But(object sender, RoutedEventArgs e)
    {
        FileOpenPicker open = new FileOpenPicker();
        open.SuggestedStartLocation = PickerLocationId.PicturesLibrary;
        open.ViewMode = PickerViewMode.Thumbnail;

        // Filter to include a sample subset of file types
        open.FileTypeFilter.Clear();
        open.FileTypeFilter.Add(".bmp");
        open.FileTypeFilter.Add(".png");
        open.FileTypeFilter.Add(".jpeg");
        open.FileTypeFilter.Add(".jpg");

        // Open a stream for the selected file
        StorageFile file = await open.PickSingleFileAsync();

        var stream = await file.OpenStreamForReadAsync();
        var bytes = new byte[(int)stream.Length];
        stream.Read(bytes, 0, (int)stream.Length);

        string encodedFile = Convert.ToBase64String(bytes);



        var values = new Dictionary<string, string>
       {
        { "kod", "111" },
        { "id_user", user.Id },
        { "image", encodedFile },
        { "title", "MyText" },
        { "text", "1234526" }
       };

        var content = new System.Net.Http.FormUrlEncodedContent(values);

        var response = await client.PostAsync("http://MyUri/tape.php", content);

        var responseString = await response.Content.ReadAsStringAsync();


    }