C# 不允许从数据类型nvarchar隐式转换为varbinary（max），上载文件

上载文件时会出现此错误，即使我在SQL中的列数据类型已经是

varbinary

。我不知道为什么我的参数

@FileUpload

是一个

nvarchar

。通过使用datatable函数，我可以方便地将其整体存储并发送到数据库，我还使用了

UserDefinedTableType

，我的数据类型已经是

varbinary

  public ActionResult UpdateClearanceItems(string TranNo, string CompanyID, string AtmCard, string FleetCard, string HmoCard,
          string  Uniform, string RSA, string EducationBenefitsRSA, string AmaBankLoan, string UsedSL,
          string ProratedSL, string KingsTreat, string LastPayroll, string OthersHr, string remarksCompanyID, 
          string remarksAtmCard, string remarksFleetCard, string remarksHmoCard, string remarksUniform, 
          string remarksRSA, string remarksEducationBenefitsRSA , string remarksAmaBankLoan, string remarksUsedSL, 
          string remarksProratedSL, string remarksKingsTreat, string remarksLastPayroll, string remarksOthersHr,
          HttpPostedFileBase[] FileUpload)
    {
        dynamic user = Session["UserProfile"];
        string UserID = user[0].UserID.ToString();

        DataTable dtItems = new DataTable();
        dtItems.Columns.Add("FileName", typeof(string));
        dtItems.Columns.Add("ContentType", typeof(string));
        dtItems.Columns.Add("Data", typeof(string));

        foreach (var file in FileUpload)
        {
            byte[] bytes;

            using (BinaryReader br = new BinaryReader(file.InputStream))
            {
                bytes = br.ReadBytes(file.ContentLength);
            }

            dtItems.Rows.Add(file.FileName, file.ContentType, bytes);

        }

        using (SqlConnection con = new SqlConnection(GlobalFunction.GetConnection("PayrollConnect")))
        {
            con.Open();

            try
            {
                SqlCommand cmd = new SqlCommand("spm_EmpClearancePending", con);
                cmd.CommandTimeout = 1000000;
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.AddWithValue("@TranNo", TranNo.ToString());
                cmd.Parameters.AddWithValue("@UserID", UserID.ToString());
                cmd.Parameters.AddWithValue("@CompanyID", CompanyID.ToString());
                cmd.Parameters.AddWithValue("@AtmCard", AtmCard.ToString());
                cmd.Parameters.AddWithValue("@FleetCard", FleetCard.ToString());
                cmd.Parameters.AddWithValue("@HmoCard", HmoCard.ToString());
                cmd.Parameters.AddWithValue("@Uniform", Uniform.ToString());
                cmd.Parameters.AddWithValue("@RSA", RSA.ToString());
                cmd.Parameters.AddWithValue("@EducationBenefitsRSA", EducationBenefitsRSA.ToString());
                cmd.Parameters.AddWithValue("@AmaBankLoan", AmaBankLoan.ToString());
                cmd.Parameters.AddWithValue("@UsedSL", UsedSL.ToString());
                cmd.Parameters.AddWithValue("@ProratedSL", ProratedSL.ToString());
                cmd.Parameters.AddWithValue("@KingsTreat", KingsTreat.ToString());
                cmd.Parameters.AddWithValue("@LastPayroll", LastPayroll.ToString());
                cmd.Parameters.AddWithValue("@OthersHr", OthersHr.ToString());
                cmd.Parameters.AddWithValue("@remarksCompanyID", remarksCompanyID.ToString());
                cmd.Parameters.AddWithValue("@remarksAtmCard", remarksAtmCard.ToString());
                cmd.Parameters.AddWithValue("@remarksFleetCard", remarksFleetCard.ToString());
                cmd.Parameters.AddWithValue("@remarksHmoCard", remarksHmoCard.ToString());
                cmd.Parameters.AddWithValue("@remarksUniform", remarksUniform.ToString());
                cmd.Parameters.AddWithValue("@remarksRSA", remarksRSA.ToString());
                cmd.Parameters.AddWithValue("@remarksEducationBenefitsRSA", remarksEducationBenefitsRSA.ToString());
                cmd.Parameters.AddWithValue("@remarksAmaBankLoan", remarksAmaBankLoan.ToString());
                cmd.Parameters.AddWithValue("@remarksUsedSL", remarksUsedSL.ToString());
                cmd.Parameters.AddWithValue("@remarksProratedSL", remarksProratedSL.ToString());
                cmd.Parameters.AddWithValue("@remarksKingsTreat", remarksKingsTreat.ToString());
                cmd.Parameters.AddWithValue("@remarksLastPayroll", remarksLastPayroll.ToString());
                cmd.Parameters.AddWithValue("@remarksOthersHr", remarksOthersHr.ToString());

                cmd.Parameters.AddWithValue("@FileUpload"  ,dtItems);

                cmd.ExecuteNonQuery();
            }
            catch(Exception err)
            { }
        }

        return RedirectToAction("ClearanceDashboard", "Clearance", new { Message = "Done" });
    }

数据表中

“Data”

列的类型不应为

字符串

，而应为

字节[]

-更改此项：

 dtItems.Columns.Add("Data", typeof(string));

为此：

 dtItems.Columns.Add("Data", typeof(byte[]));

---

不应

dtItems.Columns.Add（“数据”，typeof（字符串））是另一种类型吗？哦，我明白了，这就是为什么它是一个nvarchar，但是我如何才能将它转换为varbinary乐意帮助：-）