如何在asp.net c# web表单应用程序中将隐藏字段中的值转换为整数

我有一个名为hdn_ven_id的隐藏字段，当网格中的一行被选中时，它被填充为主键值(整数)。

protected void rg_vendors_SelectedIndexChanged(object sender, EventArgs e)
{
    foreach (GridDataItem item in rg_vendors.SelectedItems)
    {
        hdn_ven_id.Value = item["venId"].Text;                
    }
}

然后我使用hdn_ven_id的值在SqlCommand中填充@venIdFk。

protected void newDocUpldBtn_Click(object sender, EventArgs e)
{ ...
    new_doc_cmd.Parameters.AddWithValue("@venIdFk", hdn_ven_id.Value);
...}

我得到以下错误:

将nvarchar值"81"转换为数据类型int时，转换失败。

81是正确的主键值，因此我知道隐藏字段正在捕获正确的值。

我已经回顾了几个线程，比如这个(将隐藏字段转换为整数)如何将隐藏字段的值从nvarchar转换为整数。然而，我不能得到隐藏字段的值进入数据库。如果我加上

int venidfk = int. parse (hdn_ven_id.Value);

到newDocUpldBtn_Click我得到错误"输入字符串格式不正确"。

如何将隐藏字段值转换为整数?

下面是newDocUpldBtn_Click:

protected void newDocUpldBtn_Click(object sender, EventArgs e)
{
    int venidfk = int.Parse(hdn_ven_id.Value);
    //Save the file to the server and set the full path
    int i = 0;
    FileUpload fu = docFU;
    string filename = fu.FileName;
    string fnnnoext = System.IO.Path.GetFileNameWithoutExtension(fu.FileName);
    string fnnextonly = System.IO.Path.GetExtension(fu.FileName);
    if (fu.HasFile)
    {
        while (System.IO.File.Exists(Server.MapPath("~/Data/") + filename))
        {
            i++;
            filename = (fnnnoext + "(" + i.ToString() + ")" + fnnextonly);
        }
        fu.PostedFile.SaveAs(Server.MapPath("~/Data/") + filename);
        hdn_doc_path.Value = (Server.MapPath("~/Data/") + filename);
        hdn_doc_path_no_ext.Value = (fnnnoext + "(" + i.ToString() + ")" + fnnextonly);                
        SqlConnection drap_cnxn = new SqlConnection("Data Source=WDBSVCPRD01''SVCDB;Initial Catalog=drap;Integrated Security=True");
        {
            SqlCommand new_doc_cmd = new SqlCommand("Insert Into docs(docTitle, docType, docContractType, docOrg, docDept, docDesc, PriorContCd, LegCompContId, docUpldDt, docPath, docStat, venIdFk) Values(LTRIM(RTRIM(@docTitle)), LTRIM(RTRIM(@docType)), LTRIM(RTRIM(@docContractType)), LTRIM(RTRIM(@docOrg)), LTRIM(RTRIM(@docDept)), LTRIM(RTRIM(@docDesc)), LTRIM(RTRIM(@PriorContCd)), LTRIM(RTRIM(@LegCompContId)), LTRIM(RTRIM(@docUpldDt)), LTRIM(RTRIM(@docPath)), LTRIM(RTRIM(@docStat)), LTRIM(RTRIM(@venIdFk)))", drap_cnxn);
            new_doc_cmd.Parameters.AddWithValue("@docTitle", docTitleTextBox.Text);
            new_doc_cmd.Parameters.AddWithValue("@docType", docTypeDdl.SelectedValue);
            new_doc_cmd.Parameters.AddWithValue("@docContractType", docContractTypeDdl.SelectedValue);
            new_doc_cmd.Parameters.AddWithValue("@docOrg", docOrgDdl.SelectedValue);
            new_doc_cmd.Parameters.AddWithValue("@docDept", docDeptDdl.SelectedValue);
            new_doc_cmd.Parameters.AddWithValue("@docDesc", docDescTextBox.Text);
            new_doc_cmd.Parameters.AddWithValue("@PriorContCd", priorContCdTextBox.Text);
            new_doc_cmd.Parameters.AddWithValue("@LegCompContId", legCompContIdTextBox.Text);
            new_doc_cmd.Parameters.AddWithValue("@docUpldDt", DateTime.Now.ToString());
            new_doc_cmd.Parameters.AddWithValue("@docPath", hdn_doc_path.Value);
            new_doc_cmd.Parameters.AddWithValue("@docStat", "4");
            new_doc_cmd.Parameters.AddWithValue("@venIdFk", venidfk);
            drap_cnxn.Open();
            new_doc_cmd.ExecuteNonQuery();
            drap_cnxn.Close();
            if (IsPostBack)
            {
                ven_doc_det_upld_status_lbl.Text = "Your document was successfully uploaded.";
                docTitleTextBox.Text = "";
                docTypeDdl.Text = "";
                docContractTypeDdl.SelectedValue = "";
                docOrgDdl.Text = "";
                docDeptDdl.Text = "";
                docDescTextBox.Text = "";
                priorContCdTextBox.Text = "";
                legCompContIdTextBox.Text = "";
                hdn_doc_path.Value = "";
                rg_vendors.DataBind();
                fv_ven_docs.DataBind();
            }
            else
            {
                ven_doc_upld_fail_lbl.Text = "Your document failed to upload.  Please contact Compliance for assistance.";
            }
        }
    }
}

 new_doc_cmd.Parameters.AddWithValue("@venIdFk", hdn_ven_id.Value.Replace(",",""));