context.Request.Params

context.Request.Params["ISBN"]

是从页面的QueryString,Form,Cookies,ServerVariables里面检索名为"CategoryID"的值。

优先级顺序为：

QueryString->Form->Cookies->ServerVariables

 

以下是来自 Reflector 的 HttpRequest 类的部分参考代码。

public NameValueCollection Params
{
    get
    {
        if (HttpRuntime.HasAspNetHostingPermission(AspNetHostingPermissionLevel.Low))
        {
            return this.GetParams();
        }
        return this.GetParamsWithDemand();
    }
}

private NameValueCollection GetParams()
{
    if (this._params == null)
    {
        this._params = new HttpValueCollection(0x40);
        this.FillInParamsCollection();
        this._params.MakeReadOnly();
    }
    return this._params;
}

private void FillInParamsCollection()
{
    this._params.Add(this.QueryString);
    this._params.Add(this.Form);
    this._params.Add(this.Cookies);
    this._params.Add(this.ServerVariables);
}

参考资料： Reflector