自动完成文本框在C＃ASP .NET的弹出窗口中不起作用

Question

我的弹出容器中有4个字段，第二个字段的AutoPostBack为true，因此当最初尝试在TextBox中键入内容时，未单击方法（GetSearchStudentName）。如果我选择了第二个字段，然后尝试在TextBox中键入它，则可以正常工作。我该如何解决这个问题？

在StudentTrip.ascx中，

<!--Add a Student for Trip Starts here -->
<div class="form1 popup-container" runat="server">
    <div class="formAddNewRequest" id="addNewRequestTrip" runat="server">
        <div class="messages">
            <h1 class="AddTripFormHeading" style="text-align:center">Add New Trip Request</h1>
            <asp:ImageButton ID="ImageButton3" class="close-popup" runat="server" ImageUrl="~/Image/close.png" />
        </div>

        <div class="information_text">
            <label class="required"><span class="mandatory">*</span>Required Fields</label>
        </div>
        <div class="subdiv number">
            <asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="true">  
            </asp:ScriptManager>  
            <cc1:AutoCompleteExtender ServiceMethod="GetSearchStudentName" MinimumPrefixLength="1" CompletionInterval="10"  
                EnableCaching="false" CompletionSetCount="10" TargetControlID="txtUserName" ID="AutoCompleteExtender1"  
                runat="server" FirstRowSelected="false" >  
            </cc1:AutoCompleteExtender>  
            <label class="lbl_Name">Student User Name<span class="mandatory">*</span></label>
            <asp:TextBox class="txt_boxs" runat="server" ID="txtStdName"></asp:TextBox>
            <%--<asp:RequiredFieldValidator class="errorfield" ValidationGroup='GrpVal' ID="empUserName" runat="server" ControlToValidate="txtUserName"
                ErrorMessage="Enter UserName" ForeColor="Red" Font-Size="Small"></asp:RequiredFieldValidator>--%>
        </div>
        <div class="subdiv">
            <label class="lbl_Name">Destination<span class="mandatory">*</span></label>
            <asp:DropDownList class="status" ID="AddDestination"  runat="server" OnSelectedIndexChanged="DropDownRequestTime" AutoPostBack="true" >
               <%-- <asp:ListItem Selected="True">Select</asp:ListItem>--%>
            </asp:DropDownList>
            <asp:RequiredFieldValidator ID="RequiredFieldValidator3" runat="server" ErrorMessage="Choose Destination" ForeColor="Red" InitialValue="0" ControlToValidate="AddDestination" ValidationGroup="GrpVal"></asp:RequiredFieldValidator>
        </div>
        <div class="subdiv">
            <label class="lbl_Name">Trip Time<span class="mandatory">*</span></label>
            <asp:DropDownList class="status" ID="AddTripTime" runat="server" OnSelectedIndexChanged="DropDownRequestEnroute" AutoPostBack="true">
               <%-- <asp:ListItem Selected="True">Select</asp:ListItem>--%>
            </asp:DropDownList>
            <asp:RequiredFieldValidator ID="RequiredFieldValidator4" runat="server" ErrorMessage="Choose Trip Time" ForeColor="Red" InitialValue="0" ControlToValidate="AddTripTime" ValidationGroup="GrpVal"></asp:RequiredFieldValidator>
        </div>
        <div class="subdiv">
            <label class="lbl_Name">Drop Point<span class="mandatory">*</span></label>
            <asp:DropDownList class="status" ID="AddDropPoint" runat="server" AutoPostBack="false" >
               <%-- <asp:ListItem Selected="True">Select</asp:ListItem>--%>
            </asp:DropDownList>
            <asp:RequiredFieldValidator ID="RequiredFieldValidator5" runat="server" ErrorMessage="Choose Drop Point" ForeColor="Red" InitialValue="0" ControlToValidate="AddDropPoint" ValidationGroup="GrpVal"></asp:RequiredFieldValidator>
        </div>
        <div style="margin-left:40px;">
            <asp:Button ID="Save_Trip_Id" class="ava-btn primary-btn" CssClass="AddTripFormAddButton" runat="server" Text="Submit" OnClick="addNewUserTrip_Click" ValidationGroup="GrpVal" />
            <asp:Button ID="Cancel_Trip_Id" class="ava-btn secondary-btn" CssClass="AddTripFormCancelButton" runat="server" Text="Cancel" />
        </div>
    </div>
</div>
<!--Add a Student for Trip Ends here -->

在StudentTrip.aspx页面中，

[System.Web.Script.Services.ScriptMethod()]
        [System.Web.Services.WebMethod]
        public static List<string> GetSearchStudentName(string prefixText)
        {
            DataTable Result = new DataTable();
            string str = "Select StudentName from StudentDetails where StudentName like '" + prefixText + "' + '%'";
            da = new SqlDataAdapter(str, con);
            dt = new DataTable();
            da.Fill(dt);
            List<string> Output = new List<string>();
            for (int i = 0; i < dt.Rows.Count; i++)
                Output.Add(dt.Rows[i][0].ToString());
            return Output;
        }

我期望的是，最初我尝试键入名称时，应该点击该方法并在AutoCompleteTextBox中检索该名称。