我AP preciate既previous答案，他们是有用的，但不正是我一直在寻找。考虑到反应和做更多的研究，我张贴我的解决方案，这样也许这将帮助别人之后。

I appreciate both previous answers and they were helpful but not exactly what I was looking for. After considering the responses and doing more research I'm posting my solution so that maybe it will help someone else.

按钮code：

 <asp:Button ID="btnSave" OnClick="btnSaveClick" runat="server" Text="Save" OnClientClick="return CheckForVersion()" />

使用Javascript：

Javascript:

<script language="javascript">
    function CheckForVersion() {
        PageMethods.CheckForVersion(aspnetForm.ctl00$ContentPlaceHolder1$ddlPageName2.value, aspnetForm.ctl00$ContentPlaceHolder1$txtContentName2.value, OnSucceeded, OnFailed);
        return false;
    }

    function OnSucceeded(results) {
       if(results) {
            //version exists so prompt user
            if(confirm("Version already exists. Do you want to overwrite?")) {
                __doPostBack('ctl00$ContentPlaceHolder1$btnSave','');
            }
        }
        else
        {
            //version does not exist so save it without prompting user
            __doPostBack('ctl00$ContentPlaceHolder1$btnSave',''); 
        }

    }

    function OnFailed(error) {
        // handle pagemethod error
        alert(error.get_message());
    }

</script>

使用C＃2.1亚音速：

C# using Subsonic 2.1:

[WebMethod]
    public static bool CheckForVersion(string pageName, string versionName)
    {
        PageContentCollection pages = new PageContentCollection().Where("pageName", pageName).Where("versionName", versionName).Load();
        if (pages.Count > 0)
            return true;
        else
            return false;            
    }