asp.net ajax控件检测名称是否存在

<asp:TextBox ID="CompanyName" runat="server" AutoPostBack="True"  
                ontextchanged="CompanyName_TextChanged"></asp:TextBox> 
                     </td> 

      <td width="238"> 
          <asp:ScriptManager ID="ScriptManager1" runat="server"> 
            </asp:ScriptManager> 
            <asp:UpdatePanel ID="UpdatePanel1" runat="server"> 
                <ContentTemplate> 
                    <asp:Label ID="LblCheckName" runat="server" Font-Size="12px"  
                        ForeColor="#FF3300" Visible="False"></asp:Label> 
                </ContentTemplate> 
                <Triggers> 
                    <asp:AsyncPostBackTrigger ControlID="CompanyName" EventName="TextChanged" /> 
                </Triggers> 
            </asp:UpdatePanel> 
            <asp:UpdateProgress ID="UpdateProgress1" runat="server"  
                AssociatedUpdatePanelID="UpdatePanel1"> 
                <ProgressTemplate> 
                    正在检测名称.. 
                </ProgressTemplate> 
            </asp:UpdateProgress> 



      /// <summary> 
        /// ajax控件检测 
        /// </summary> 
        /// <param name="sender"></param> 
        /// <param name="e"></param> 
        protected void CompanyName_TextChanged(object sender, EventArgs e) 
        { 
            string cpName = this.CompanyName.Text.Trim(); 
            if (chekCompanyName(cpName)) 
            { 
                LblCheckName.Text = "允许"; 
                this.LblCheckName.Visible = true; 
                this.Button1.Enabled = true; 
            } 
            else 
            { 
                LblCheckName.Text = "数据库中不存在该公司，不允许添加"; 
                this.LblCheckName.Visible = true; 
                this.Button1.Enabled = false; 
            } 
           
            
        }