SQL错误必须声明标量变量

        private void FillInvoiceList()
    {
        DataTable distinctInvoice = new DataTable();
        using (SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["APOS_CONNECTION_STRING"].ConnectionString))
        {
            conn.Open();
            SqlCommand cmd = new SqlCommand("Select distinct svc_tag from data where rep_name = @value");
            cmd.Parameters.AddWithValue("@value", this.DropDownList1.SelectedItem.Text);
            SqlDataAdapter sqlDataAdapter = new SqlDataAdapter(cmd.CommandText, conn.ConnectionString);
            sqlDataAdapter.Fill(distinctInvoice);
        }
        foreach (DataRow row in distinctInvoice.Rows)
        {
            this.ListBox1.Items.Add(row["svc_tag_dim_invoice_num"].ToString());
        }
    }

我有这个代码,当我调用Fill(distinctionvoice)时会出现这个错误

必须声明标量变量“@value”

正在从DropDownList 1中的SelectedIndexChanged事件调用My FillInvoiceList()方法。DropDownList1.SelectedItem.Text的值似乎正确。

谢谢你的帮助。