当我尝试打印用户控件时，当我使用异步方法获取数据时，datagrid不显示记录

本文介绍了当我尝试打印用户控件时，当我使用异步方法获取数据时，datagrid不显示记录的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我有一个具有数据网格的用户控件。我想打印这个用户控件。我知道如何打印此用户控件，并显示datagrid的行，当我使用同步方法从数据库获取数据时，使用实体核心2.0。但是，如果我使用EF的async
方法来获取数据，则不会显示它们的行。

I have a user control that has a datagrid. I want to print this user control. I know how to print this user control, and show the rows of the datagrid, when I use a sync method to get the data from database, using entity core 2.0. However, if I use the async method of EF to get the data, the rows it aren't shown.

我正在使用MVVM模式，但我尝试过使用代码背后，结果是一样的。所以问题我想在构造函数中使用异步方法。

I am using the MVVM patter, but I have tried using code behind and the result is the same. So the problem I guess it is to use async methods in the constructor.

我的代码是这样的：

public MyViewModel()
{
    Task.Run(() => getDataAsync().ConfigureAwait(false));

// getData（）;
}

private ObservableCollection< MyType> _myItems = new ObservableCollection< MyType>（）;
public ObservableCollection< MyType> MyItems
{
get {return _myItems; }
设置
{
_myItems = value;
base.RaisePropertyChangedEvent（" MyItems"）;
}
}

私有异步任务getDataAsync（）
{
using（ContextEfCore myDbContext = new ContextEfCore（_optionsDbContext））
{
MyItems = new ObservableCollection< MyType>（等待myDbCOntext.MyType.ToListAsync（））;
}
}

private void getData（）
{
using（ContextEfCore myDbContext = new ContextEfCore（_optionsDbContext））
{
MyItems = new ObservableCollection< MyType>（等待myDbCOntext.MyType.ToList（））;
}
}

//getData();}private ObservableCollection<MyType> _myItems = new ObservableCollection<MyType>();public ObservableCollection<MyType> MyItems{ get { return _myItems; } set { _myItems = value; base.RaisePropertyChangedEvent("MyItems"); }}private async Task getDataAsync(){ using(ContextEfCore myDbContext = new ContextEfCore(_optionsDbContext)) { MyItems = new ObservableCollection<MyType>(await myDbCOntext.MyType.ToListAsync()); }}private void getData(){ using(ContextEfCore myDbContext = new ContextEfCore(_optionsDbContext)) { MyItems = new ObservableCollection<MyType>(await myDbCOntext.MyType.ToList()); }}

当我使用getDataAsync（）时不起作用，但是当我使用getData（）时它可以工作。

When I use getDataAsync() does't work but when I use getData() it works.

我如何使用asyn方法使其有效？我想避免使用该方法的两个版本，async和sync。

How could I use the asyn method to make it works? I would like to avoid to have the two versión of the method, async and sync.

谢谢。

编辑：我将添加我正在使用的完整代码。

I will added the complete code that I am using.

我要打印的视图的视图模型

My view model of the view that I want to print

{
	public MyViewModelToPrint()
	{
		Task.Run(() => getDataAsyncAsync());

		//getData(); //this works
	}




	private ObservableCollection<MyType> _myItems = new ObservableCollection<MyType>();
	public ObservableCollection<LineasFacturas> MyItems
	{
		get { return _myItems; }
		set
		{
			_myItems = value;
			base.RaisePropertyChangedEvent("MyItems");
		}
	}





	private async Task getDataAsync()
	{
		MyItems = new ObservableCollection<MyType>((await Repository.getDataAsync()));
	}



	private void getData()
	{
		MyItems = new ObservableCollection<MyType>((await Repository.getData()));

	}
}

我要打印的视图：

<UserControl x:Class="GTS.CMMS.Client.Views.docFacturasView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             mc:Ignorable="d"
             Height="29.9cm" Width="21.0cm">
    <Grid>
            <DataGrid VerticalAlignment="Stretch" HorizontalAlignment="Stretch" Margin="5,5,5,5" Grid.Column="0" Grid.Row="0"
                      ItemsSource="{Binding MyItems}">
            </DataGrid>
        </Grid>
</UserControl>

尝试打印视图的主视图模型：

The main view model that tries to print the view:

public void printDocument()
{
	//Just print to PDF with the default printer of Windows 10 without prompting the selection of the printer
	System.Drawing.Printing.PrintDocument pd = new System.Drawing.Printing.PrintDocument();
	pd.PrinterSettings.PrintFileName = @"d:\dummy-02.pdf";
	pd.PrinterSettings.PrinterName = "Microsoft Print to PDF";
	pd.PrinterSettings.PrintToFile = true;
	pd.PrintPage += PrintPage;
	pd.Print();
}






private void PrintPage(object o, System.Drawing.Printing.PrintPageEventArgs e)
{
	MyViewToPrint myViewToPrint = new MyViewToPrint();
	MyViewModelToPrint myViewModelToPrint = new MyViewModelToPrint();
	myViewToPrint.DataContext = myViewModelToPrint;


	int myFactor;
	myFactor = 6;


	myViewToPrint.UpdateLayout();


	System.Windows.Media.Imaging.RenderTargetBitmap rtb = new System.Windows.Media.Imaging
	.RenderTargetBitmap(794 * myFactor, 1122 * myFactor, 96 * miFactor, 96 * myFactor, System.Windows.Media.PixelFormats.Pbgra32);
	rtb.Render(myViewToPrint);


	//convert System.Drawing.Image to WPF image
	System.Windows.Media.Imaging.PngBitmapEncoder encoder = new System.Windows.Media.Imaging.PngBitmapEncoder();
	System.IO.MemoryStream ms = new System.IO.MemoryStream();
	encoder.Frames.Add(System.Windows.Media.Imaging.BitmapFrame.Create(rtb));
	encoder.Save(ms);
	System.Drawing.Image img = System.Drawing.Image.FromStream(ms);
	e.Graphics.DrawImage(img, new System.Drawing.PointF());
}

这就是全部。

private

当我尝试打印用户控件时，当我使用异步方法获取数据时，datagrid不显示记录

问题描述

推荐答案