c# - asp:DataGrid visibility with async? -
.net 4.5.2, iis 8.5 on windows 8.1 x64. have single asp.net web site @ /localhost/.
i've got real async-puzzle here i've been wrestling 2 days now.
i'm reworking long-running reports async, can demonstrate problem simple code.
i have asp:datagrid on page i've set visible="false". should visible if populated. problem is, if code populates async don't see grid!
here's markup:
<body> <form runat="server"> <asp:datagrid id="grid" visible="false" runat="server"></asp:datagrid> </form> </body> in code-behind, code works:
void page_load() { grid.datasource = new dictionary<string, string>() { { "col1", "value1" } }; grid.databind(); grid.visible = true; } now if make 2 changes:
add async="true" @page directive replace page_load this
void page_load() { this.registerasynctask(new pageasynctask(async () => { grid.datasource = new dictionary<string, string>() { { "col1", "value1" } }; grid.databind(); grid.visible = true; })); } the grid not rendered. note i've used async keyword though there no await in delegate. have tried several things, same result:
- add await task.delay(...)
- remove async keyword , return task.fromresult(0)
i have overridden , instrumented page lifecycle events see when grid populated , how visiblity changes. output 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" , "2" on either side of grid population inside delegate. can see grid getting row , visibility gets true, yet isn't rendered. if populate grid first code sample, synchronously, well.
another note: can enclose grid in control make 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 visible="false" on asp:datagrid screws up.
what doing wrong?
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