TextBox   放到外头去 !!
就是这样!!
 <form id="form1" runat="server">
        &nbsp;<div>
            &nbsp;&nbsp;<asp:ScriptManager ID="ScriptManager1" runat="server">
            </asp:ScriptManager>
            <ajaxToolkit:AutoCompleteExtender ID="AutoCompleteExtender1" runat="server"
        TargetControlID="TextBox1"
        CompletionSetCount="12"
        EnableCaching="true"
        MinimumPrefixLength="1"
        ServicePath="sql_test.asmx"
       CompletionListElementID="Panel1"
        ServiceMethod="GetCompleteList">
            </ajaxToolkit:AutoCompleteExtender>
        </div>
        &nbsp; 
        <asp:TextBox ID="TextBox1" runat="server" ForeColor="Black"></asp:TextBox>
    </form>

解决方案 »

  1.   

    你用了Css样式吧 这个控件你用了新的css样式 什么都会变的 
    最好是原装不动的试下 
    原装的是没问题的
      

  2.   

    什么都没有用啊```
    <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %><%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head id="Head1" runat="server">    <title>Untitled Page</title>
    </head>
    <body>
        <form id="form1" runat="server">
            <asp:ScriptManager ID="ScriptManager1" runat="server" />
             
            <cc1:AutoCompleteExtender ID="AutoCompleteExtender1" runat="server" 
            TargetControlID="TextBox1" 
            CompletionSetCount="10" 
            CompletionInterval="1000"
            EnableCaching="true"
            MinimumPrefixLength= "1" 
            ServicePath="WebService.asmx"
            CompletionListElementID= "Panel1" ServiceMethod="GetCompleteList"
           >
            </cc1:AutoCompleteExtender>
            <asp:TextBox ID="TextBox1" runat="server" ForeColor= "Black"></asp:TextBox>
        </form>
    </body>
    </html>