asp.net从数据库自动完成文本框

我试图制作一个文本框，该文本框提供了来自数据库列的建议。但是，当我运行该页面时，它显示此错误。

错误-无法加载文件或程序集“ AjaxControlToolkit”或其依赖项之一。该系统找不到指定的文件。

ASP代码

<asp:ToolkitScriptManager  ID="ScriptManager1" runat="server"></asp:ToolkitScriptManager>
    <asp:AutoCompleteExtender ID="autoComplete1" runat="server"
  EnableCaching="true"
  BehaviorID="AutoCompleteEx"
  MinimumPrefixLength="2"
  TargetControlID="myTextBox"
  ServicePath="AutoComplete.asmx"
  ServiceMethod="GetCompletionList" 
  CompletionInterval="1000"  
  CompletionSetCount="20"
  CompletionListCssClass="autocomplete_completionListElement"
  CompletionListItemCssClass="autocomplete_listItem"
  CompletionListHighlightedItemCssClass="autocomplete_highlightedListItem"
  DelimiterCharacters=";, :"
  ShowOnlyCurrentWordInCompletionListItem="true"> </asp:AutoCompleteExtender>

 <td><asp:TextBox ID="TextBox2" runat="server" CssClass="text_box" autocomplete="off"></asp:TextBox><br /><asp:RequiredFieldValidator
                            ID="RequiredFieldValidator1" runat="server" ControlToValidate="TextBox2" ErrorMessage="Please Enter Client / Company Name" style="color:#f00; font-size:11px"></asp:RequiredFieldValidator></td>

VB代码

<System.Web.Script.Services.ScriptService()> _
<WebService(Namespace:="http://tempuri.org/")> _
<WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _

Public Class AutoComplete
    Inherits System.Web.Services.WebService
    Dim cn As New SqlClient.SqlConnection()
    Dim ds As New DataSet
    Dim dt As New DataTable
    <WebMethod()> _
    Public Function GetCompletionList(ByVal prefixText As String, _
 ByVal count As Integer) As String()

        'ADO.Net
        Dim strCn As String = _
"Data Source=SONAM-PC\SQLSERVER2008R2;Initial Catalog=Brandstik2; Integrated Security=True"
        cn.ConnectionString = strCn
        Dim cmd As New SqlClient.SqlCommand
        cmd.Connection = cn
        cmd.CommandType = CommandType.Text
        'Compare String From Textbox(prefixText) 
        'AND String From Column in DataBase(CompanyName)
        'If String from DataBase is equal to String from TextBox(prefixText) 
        'then add it to return ItemList
        '-----I defined a parameter instead of passing value 
        'directly to prevent SQL injection--------'
        cmd.CommandText = "select * from BrandstikTesti Where client_name like @myParameter"
        cmd.Parameters.AddWithValue("@myParameter", "%" + prefixText + "%")

        Try
            cn.Open()
            cmd.ExecuteNonQuery()
            Dim da As New SqlDataAdapter(cmd)
            da.Fill(ds)
        Catch ex As Exception
        Finally
            cn.Close()
        End Try

        dt = ds.Tables(0)

        'Then return List of string(txtItems) as result

        Dim txtItems As New List(Of String)
        Dim dbValues As String

        For Each row As DataRow In dt.Rows

            ''String From DataBase(dbValues)
            dbValues = row("client_name").ToString()
            dbValues = dbValues.ToLower()
            txtItems.Add(dbValues)

        Next

        Return txtItems.ToArray()

    End Function
End Class