为什么从客户端调用 PageMethod 时会创建页面实例？

Question

由于 ASP.NET 中的 PageMethods 需要是静态方法并标记为 Web 方法，我的印象是调用页面方法时不会创建该特定页面的实例。

但是当我尝试在构造函数中放置一个断点时，每次调用 pagemethod 时都会遇到问题。有人可以告诉我构建实例需要什么吗？

谢谢

服务器端

public partial class PageMethod : System.Web.UI.Page
{

    public PageMethod()
    {

    }

    [System.Web.Services.WebMethod()]
    public static string GetMessage()
    {
        return "Page Method Call";
    }
}

客户端（使用 JQuery）

$.ajax({ type: 'POST',
                url: /PageMethod.aspx/GetMessage,
                data: null,
                success: onSuccess,
                contentType: "application/json; charset=utf-8",
                dataType: 'JSON',
                error: onError      
            });

Answer 1

编辑

确实调用了构造函数！！查看 pagemethod 调用的调用栈：

PageMethodTest_WebApplication3.DLL!PageMethodTest_WebApplication3._Default._Default() Line 9    C#
  App_Web_iielssqo.dll!ASP.default_aspx.default_aspx() + 0x43 bytes C#
  App_Web_iielssqo.dll!__ASP.FastObjectFactory_app_web_iielssqo.Create_ASP_default_aspx() + 0x43 bytes  C#
  System.Web.dll!System.Web.Compilation.BuildResultCompiledType.CreateInstance() + 0x21 bytes   
  System.Web.dll!System.Web.Compilation.BuildManager.CreateInstanceFromVirtualPath(System.Web.VirtualPath virtualPath, System.Type requiredBaseType, System.Web.HttpContext context, bool allowCrossApp, bool noAssert) + 0x78 bytes    
  System.Web.dll!System.Web.UI.PageHandlerFactory.GetHandlerHelper(System.Web.HttpContext context, string requestType, System.Web.VirtualPath virtualPath = {/Default.aspx}, string physicalPath) + 0x22 bytes  
  System.Web.dll!System.Web.UI.PageHandlerFactory.System.Web.IHttpHandlerFactory2.GetHandler(System.Web.HttpContext context, string requestType, System.Web.VirtualPath virtualPath, string physicalPath) + 0x29 bytes  
  System.Web.dll!System.Web.HttpApplication.MapHttpHandler(System.Web.HttpContext context, string requestType, System.Web.VirtualPath path, string pathTranslated = "C:\\Documents and Settings\\Administrator\\My Documents\\Visual Studio 2008\\Projects\\PageMethodTest_WebApplication3\\PageMethodTest_WebApplication3\\Default.aspx", bool useAppConfig) + 0xa1 bytes  

ASP.NET 引擎将请求从 pagemethod 路由到 aspx-handler-factory (PageHandlerFactory)。据我了解，这是 ASP.NET 的内部逻辑。因此它是正确的:)

现在检查 asmx-webmethod 调用：

  PageMethodTest_WebApplication3.DLL!PageMethodTest_WebApplication3.WebService1.HelloWorld() Line 22    C#
  [Native to Managed Transition]    
  [Managed to Native Transition]    
  System.Web.Extensions.dll!System.Web.Script.Services.WebServiceMethodData.CallMethod(object target, System.Collections.Generic.IDictionary<string,object> parameters) + 0x15c bytes   
  System.Web.Extensions.dll!System.Web.Script.Services.WebServiceMethodData.CallMethodFromRawParams(object target, System.Collections.Generic.IDictionary<string,object> parameters) + 0x1f bytes   
  System.Web.Extensions.dll!System.Web.Script.Services.RestHandler.InvokeMethod(System.Web.HttpContext context = {System.Web.HttpContext}, System.Web.Script.Services.WebServiceMethodData methodData = {System.Web.Script.Services.WebServiceMethodData}, System.Collections.Generic.IDictionary<string,object> rawParams) + 0x61 bytes    
  System.Web.Extensions.dll!System.Web.Script.Services.RestHandler.ExecuteWebServiceCall(System.Web.HttpContext context = {System.Web.HttpContext}, System.Web.Script.Services.WebServiceMethodData methodData) + 0x55 bytes    
  System.Web.Extensions.dll!System.Web.Script.Services.RestHandler.ProcessRequest(System.Web.HttpContext context) + 0xc bytes   
  System.Web.Extensions.dll!System.Web.Script.Services.ScriptHandlerFactory.HandlerWrapper.ProcessRequest(System.Web.HttpContext context) + 0xe bytes   
  System.Web.dll!System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() + 0xb6 bytes   

这里使用另一个 httphandler-factory - ScriptHandlerFactory。

PS Moorthy，谢谢！好问题 :) '生活和学习！'

---

static / [WebMethod] - 仅由 ajax 调用 cos 页面方法（无需创建页面）。

如果您想拥有 Page 实例，您应该使用 UpdatePanel 或 AJAX.NET 控件（例如 DevExpress、AjaxToolKit）。