我查询 列表里面只有一条信息 为什么页面会重复显示 2 条

<asp:TextBox ID="tb_doctor" runat="server" style=" height:20px; width:100px; float:left;" ></asp:TextBox>
              
                <asp:ImageButton runat="server" ImageUrl="img/1.png" Width="30px" Height="30px"
                                    onclick="Unnamed1_Click" />  

<asp:DataList ID="DataList23" runat="server" RepeatDirection="Horizontal">
                                    <ItemTemplate>
                                        <div style="width:auto; height:auto;">
                                            <img ID="Image1" runat="server" src='<%#Bind("authorUrl")%> ' style=" height:150px;border:none; " /></a>
                                        </div>
                                        <div style="width:100%; height:100%; margin-top:10px;font-size:12px;float:left; text-align:center;">
                                            <asp:Label ID="Label1" runat="server" Text='<%#Bind("AuthorName")%>'></asp:Label>&nbsp;教授
                                        </div>
                                        <div style="width:100%; height:100%; margin-top:10px;font-size:12px; float:left;text-align:center;">专业:&nbsp;
                                            <asp:Label ID="Label3" runat="server" Text='<%#Bind("AuthorSubject")%>'></asp:Label>
                                        </div>
                                </ItemTemplate>
                                </asp:DataList>

protected void Unnamed1_Click(object sender, ImageClickEventArgs e)
    {
        DataTable dt = author.servers(this.tb_doctor.Text);
        if (dt.Rows.Count == 0)
        {
            ClientScript.RegisterStartupScript(this.GetType(), "Error", "<script>alert('输入不正确，请重新输入！')</script>");
        }
        this.tb_doctor.Text = "";
        this.DataList23.DataSource = dt;
        this.DataList23.DataBind();

    }

///<summsry>
        ///专家查询
        ///AuthorName 专家名字
        ///</summsry>
        public static DataTable selects(string AuthorName)
        {
            StringBuilder strsql = new StringBuilder();
            strsql.Append("select AuthorName,authorUrl,AuthorSubject from authoritative ");
            if (!AuthorName.Equals(""))
            {
                strsql.AppendFormat("where AuthorName like '%" + AuthorName + "%' ");
            }
            return DBHelper.GetDataSet(strsql.ToString());
        }