第一选择选项总是返回登录错误，即使密码在数据库中是正确的

我有一个相当奇怪的问题与ASP。净c#。

似乎我可以登录与任何其他选项在我的选择下拉除了第一个。我已经检查了数据库中的密码，它是正确的。

有人知道为什么会这样吗?

下面是我的代码:

. aspx

<form id="loginForm" runat="server">
        <asp:Login runat="server" OnAuthenticate="Login1_Authenticate" Width="293px" Height="172px"
            ID="Login_Box">
            <LayoutTemplate>
                <!-- department -->
                <div id="dept" style="text-align: left">
                    Department<br />
                    <asp:DropDownList ID="UserName" runat="server" DataSourceID="SqlDataSource1" DataTextField="dept"
                        DataValueField="id" DataMember="DefaultView">
                    </asp:DropDownList>
                    <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:team13ConnectionString %>"
                        SelectCommand="SELECT [id], [dept] FROM [ts_dept] ORDER BY [dept]"></asp:SqlDataSource>
                </div>
                <!-- password -->
                <div id="pass" style="text-align: left">
                    Password:<br />
                    <asp:TextBox ID="Password" runat="server" TextMode="Password"></asp:TextBox>
                    <asp:RequiredFieldValidator ID="PasswordRequired" runat="server" ControlToValidate="Password"
                        ErrorMessage="Password is required." ToolTip="Password is required." ValidationGroup="Login1"
                        ForeColor="Red" Display="Dynamic">Password is required.</asp:RequiredFieldValidator>
                </div>
                <!-- failure text -->
                <div style="text-align: left; color: Red">
                <asp:Literal ID="FailureText" runat="server" EnableViewState="False" Mode="Encode"></asp:Literal>
                </div>
                <br />
                <!-- sign in button -->
                <div class="btn" style="float: right" runat="server">
                    <asp:Button ID="LoginButton" runat="server" CommandName="Login" Text="Log In" ValidationGroup="Login1"
                        CssClass="cupid-green"/>
                </div>
            </LayoutTemplate>
        </asp:Login>
        </form>

Login.aspx.cs

using System;
using System.Collections;
using System.Configuration;
using System.Data.SqlClient;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Web.Configuration;
public partial class login : System.Web.UI.Page
{
    protected void Login1_Authenticate(object sender, AuthenticateEventArgs e)
    {
        string username = Login_Box.UserName;
        string pwd = Login_Box.Password;
        string strConn;
        strConn = WebConfigurationManager.ConnectionStrings["team13ConnectionString"].ConnectionString;
        SqlConnection Conn = new SqlConnection(strConn);
        Conn.Open();
        string sqlUserName;
        sqlUserName = "SELECT id,pass FROM ts_dept ";
        sqlUserName += " WHERE (id ='" + username + "')";
        sqlUserName += " AND (pass ='" + pwd + "')";
        SqlCommand com = new SqlCommand(sqlUserName, Conn);
        string CurrentName;
        CurrentName = (string)com.ExecuteScalar();
        if (CurrentName != null)
        {
            Session["UserAuthentication"] = username;
            Session.Timeout = 1;
            Response.Redirect("Default.aspx");
        }
        else
        {
            Session["UserAuthentication"] = "";
        }
    }
}