asp:DataGrid 可见性与异步? [英] asp:DataGrid visibility with async?
问题描述
.NET 4.5.2，Windows 8.1 x64 上的 IIS 8.5.我在/localhost/有一个 ASP.NET 网站.
这里有一个真正的异步谜题，我已经折腾了两天了.
我正在修改一些长期运行的报告以使其异步，但我可以用非常简单的代码来演示我的问题.
我的页面上有一个 asp:DataGrid，我最初将其设置为visible="false".它应该只在填充时可见.我的问题是，如果填充它的代码是异步的，我就看不到网格！
这是标记:
<form runat="服务器"><asp:datagrid ID="grid"visible="false" Runat="server"></asp:datagrid></表单>在代码隐藏中，此代码有效:
void Page_Load(){grid.DataSource = new Dictionary(){{ "col1", "value1" }};grid.DataBind();grid.Visible = true;} 现在，如果我进行两项更改:
在@Page 指令中添加 Async="True"用这个替换 Page_Load
void Page_Load(){this.RegisterAsyncTask(new PageAsyncTask(async () =>{grid.DataSource = new Dictionary(){{ "col1", "value1" }};grid.DataBind();grid.Visible = true;}));} 网格未呈现.请注意，即使委托中没有 await，我也使用了 async 关键字.我尝试了几件事，结果都一样:
- 添加一个 await Task.Delay(...)
- 删除 async 关键字并返回 Task.FromResult(0)
我已经覆盖并检测了页面生命周期事件，以查看网格何时填充以及其可见性如何变化.这是我看到的输出:
OnPreInit: Visible=False Rows=0 Thread=63OnInit: Visible=False Rows=0 Thread=63OnInitComplete:可见=假行=0线程=63OnPreLoad:可见=假行=0 线程=63OnLoad:可见=假行=0线程=63OnLoadComplete:可见=假行=0线程=63OnPreRender:可见 = 假行 = 0 线程 = 63异步 1:可见 = 假行 = 0 线程 = 63异步 2:可见 = 真行 = 1 线程 = 63OnPreRenderComplete:可见 = 真行 = 1 线程 = 63OnSaveStateComplete: Visible=True Rows=1 线程=63渲染 1:可见 = 真行 = 1 线程 = 63渲染 2:可见 = 真行 = 1 线程 = 63Async 1"和2"位于委托内网格群的两侧.您可以看到网格正在排成一行，并且其可见性变为真实，但尚未呈现.如果我用我的第一个代码示例同步填充网格，一切都很好.
另一个注意事项:我可以将网格包含在另一个控件中以使其工作:
<form runat="服务器"><div id="container"visible="false" runat="server"><asp:datagrid ID="grid" Runat="server"></asp:datagrid></表单>
似乎是 asp:datagrid 本身的 visible="false" 搞砸了.
我做错了什么?
假设 RegisterAsyncTask 返回一个 promise，试试
this.RegistreAsyncTask(异步 () =>{返回新字典<字符串，字符串>(){{ "col1", "value1";}};}).then(dataSource => {grid.DataSource = dataSource; grid.visible = true})想法是 async 在不同的后台线程中运行，而 Promise 在 UI 线程 中解决(与类似的 android 概念有关)
.NET 4.5.2, IIS 8.5 on Windows 8.1 x64. I have a single ASP.NET web site at /localhost/.
I've got a real async-puzzle here that I've been wrestling with for two days now.
I'm reworking some long-running reports to be async, but I can demonstrate my problem with very simple code.
I have an asp:DataGrid on my page that I've initially set visible="false". It should only be visible if it is populated. My problem is, if the code that populates it is async I don't see the grid!
Here's the markup:
<body>
<form runat="server">
<asp:datagrid ID="grid" visible="false" Runat="server"></asp:datagrid>
</form>
</body>
In the code-behind, this code WORKS:
void Page_Load()
{
grid.DataSource = new Dictionary<string, string>()
{
{ "col1", "value1" }
};
grid.DataBind();
grid.Visible = true;
}
Now if I make two changes:
Add Async="True" to the @Page directive Replace Page_Load with this
void Page_Load()
{
this.RegisterAsyncTask(new PageAsyncTask(async () =>
{
grid.DataSource = new Dictionary<string, string>()
{
{ "col1", "value1" }
};
grid.DataBind();
grid.Visible = true;
}));
}
The grid is not rendered. Note that I've used the async keyword even though there is no await in the delegate. I have tried several things, all with the same result:
- Add an await Task.Delay(...)
- Remove the async keyword and Return Task.FromResult(0)
I have overridden and instrumented the page lifecycle events to see when the grid is populated and how its visiblity changes. This is the output I see:
OnPreInit: Visible=False Rows=0 Thread=63
OnInit: Visible=False Rows=0 Thread=63
OnInitComplete: Visible=False Rows=0 Thread=63
OnPreLoad: Visible=False Rows=0 Thread=63
OnLoad: Visible=False Rows=0 Thread=63
OnLoadComplete: Visible=False Rows=0 Thread=63
OnPreRender: Visible=False Rows=0 Thread=63
Async 1: Visible=False Rows=0 Thread=63
Async 2: Visible=True Rows=1 Thread=63
OnPreRenderComplete: Visible=True Rows=1 Thread=63
OnSaveStateComplete: Visible=True Rows=1 Thread=63
Render 1: Visible=True Rows=1 Thread=63
Render 2: Visible=True Rows=1 Thread=63
"Async 1" and "2" are on either side of the grid population inside the delegate. You can see the grid is getting a row and its visibility gets true, yet it isn't rendered. If I populate the grid with my first code sample, synchronously, all is well.
Another note: I can enclose the grid in another control to make it work:
<body>
<form runat="server">
<div id="container" visible="false" runat="server">
<asp:datagrid ID="grid" Runat="server"></asp:datagrid>
</div>
</form>
</body>
It seems to be the visible="false" on the asp:datagrid itself that screws this up.
What am I doing wrong?
Assuming RegisterAsyncTask returns a promise, try
this.RegistreAsyncTask(
async () =>
{
return new Dictionary<string, string>(){
{ "col1", "value1" }
};
}
).then(dataSource => {grid.DataSource = dataSource; grid.visible = true})
Idea being the async runs in a different background thread and the Promise is resolved in the UI thread (relating to similar android concepts)
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