Error reading byte array passed as parameter

Question

That is the mistake:

The input is not a valid Base 64 character string, as contains a character that is not base 64, more than two characters from or an illegal character between the characters of filling up.

This is my view, where I pass the parameters coming from my grid(table):

<td>
  @Html.ActionLink("Download", "Download", new { item.ID_SOLIC_RELATORIO,    item.POC_RELATORIO.NM_RELATORIO, item.BL_RELATORIO })
</td>

This is the method in my controller that receives the parameters:

public FileResult Download(int ID_SOLIC_RELATORIO, string NM_RELATORIO, byte[] BL_RELATORIO)
        {
            int _arquivoId = 1;
            var arquivos = oModelFiles.GetFileReport(ID_SOLIC_RELATORIO, NM_RELATORIO, BL_RELATORIO);

            string nomeArquivo = (from arquivo in arquivos
                                  where arquivo.arquivoID == _arquivoId
                                  select arquivo.arquivoCaminho).First().ToString();

            string contentType = "application/pdf";
            //Os parametros para o arquivo são
            //1. o caminho do aruivo on servidor
            //2. o tipo de conteudo do tipo MIME
            //3. o parametro para o arquivos salvo pelo navegador
            return File(nomeArquivo, contentType, "novoreport.pdf");
        }

And this is my Model that gets the values from the controller as well:

public List<PDFFiles> GetFileReport(int _Id_Solic_Relat, string NM_RELATORIO, byte[] BL_RELATORIO)
        {
            //POC_SOLIC_RELATORIO relat = new POC_SOLIC_RELATORIO();
            List<PDFFiles> lstFiles = new List<PDFFiles>();
            //DirectoryInfo dirInfo = new DirectoryInfo(HostingEnvironment.MapPath("~/Arquivos"));
            DirectoryInfo dirInfo = new DirectoryInfo("C:/Relatemp/");
            string arquivoCaminho = string.Empty;
            int i = 0;
            foreach (var item in dirInfo.GetFiles())
            {
                lstFiles.Add(new PDFFiles()
                {
                    arquivoID = _Id_Solic_Relat,
                    arquivoNome = NM_RELATORIO,
                    arquivoBinario = BL_RELATORIO,
                    arquivoCaminho = dirInfo.FullName + @"\" + item.Name
                });
                i = i + 1;
            }
            return lstFiles;
        }

How do I resolve the issue of error? I tried to give a Convert.FromBase64String(), but this did not work, even passing the arguments to string. How do I do this? How do I convert or remove the strange characters claimed in the error?

I got this link on the net, but I couldn’t resolve