Gridview 列数在启动时始终为 0

Question

下面的代码在我的应用程序启动时被调用。数据源确实有 1 个项目。但是消息框永远不会显示。现在，当第一次绘制用户界面时，gridview 确实有一行。如果我在按钮上再次调用代码，则消息框将正确显示。这里发生了什么，我该如何修复它（我认为它与线程有关，因为 radGridview 实际上还没有更新）？

用于绑定网格的 C# 代码

// Bind list to gridview
this.radGridViewFiles.BeginInvoke((MethodInvoker)(() => this.radGridViewFiles.DataSource = null));
this.radGridViewFiles.BeginInvoke((MethodInvoker)(() => this.radGridViewFiles.DataSource = MyGlobals.ListOfItemsToControl.Concat(MyGlobals.lstNewItems.Where(i => i.sItemRequestStatus == "Add").ToList()))); //

if (radGridViewFiles.Columns.Count > 0)
{
   RadMessageBox.Show(" This messagebox should show on startup but it does not - But if i call all this code again manually on a button press it does show ??? !!");

}

Answer 1

您正在异步绑定 GridView，这就是为什么当您检查 Column 计数时它仍然为零的原因。

我建议你在同一个线程中绑定或者等待异步操作完成。

根据您的要求，这里是使用EndInvoke 的代码示例。虽然如果你把它放在一个方法中 - 你不会从异步调用中获得任何东西。

// You don't need this, so i commented it out.
// it's excessive, you are going to overwrite this variable anyway
// this.radGridViewFiles.BeginInvoke((MethodInvoker)(() =>this.radGridViewFiles.DataSource = null));

var asyncRes = this.radGridViewFiles.BeginInvoke((MethodInvoker)(() => this.radGridViewFiles.DataSource = MyGlobals.ListOfItemsToControl.Concat(MyGlobals.lstNewItems.Where(i => i.sItemRequestStatus == "Add").ToList())));

// This method blocks until previous operation is done
// It's quite pointless. In real life you should call it somewhere from another thread
// While qui thread is unblocked and displaying progress bar or something like this. 
this.radGridViewFiles.EndInvoke(asyncRes);

// at this point, binding is complete
if (radGridViewFiles.Columns.Count > 0)
{
   RadMessageBox.Show(" This messagebox should show on startup but it does not - But if i call all this code again manually on a button press it does show ??? !!");
}