C# 第一次导航到页面时阻止主线程 问题

当应用程序启动时，将打开一个空的

主页

页面。我转到

供应商

选项卡，它会冻结几秒钟（我可以看到UI被冻结）。之后，将显示

供应商

页面。元素包含来自数据库的数据

您可能认为锁是由从数据库加载数据引起的。但是它出现在

async/await

方法中

如果在加载一个

供应商后返回
主页
并返回
供应商
，则不会冻结。页面几乎立即打开。在这种情况下，数据加载机制也会发生（通过
加载事件
）

事实证明，只有在第一次访问
Vendros
页面时，冻结才是一个干净的开始。有什么问题吗

GIF

代码
查看

<i:Interaction.Behaviors>
    <ic:EventTriggerBehavior EventName="Loaded">
        <ic:InvokeCommandAction Command="{x:Bind ViewModel.PageLoadedCommand}" />
    </ic:EventTriggerBehavior>
</i:Interaction.Behaviors>



供应商视图模型

public ICommand PageLoadedCommand {get;}
private async void OnPageLoaded(RoutedEventArgs args)
{
    await VendorsService.InitializeAsync();

    BankItems = VendorsService.BankItems;
    AuthorityItems = VendorsService.AuthorityItems;
    VendorItems = VendorsService.VendorItems;
}

public ObservableCollection<VendorModel> VendorItems {get; set;}
public ObservableCollection<TwoLinesModel> BankItems {get; set;}
public ObservableCollection<TwoLinesModel> AuthorityItems{get; set;}

public partial class GenericDataService<T> : IDataService<T> where T : DomainEntity
{
    private readonly DbContext _dbContext;
    public GenericDataService(DbContext dbContext) => _dbContext = dbContext;

    public async Task<IList<T>> SelectAll()
    {
        return await _dbContext.Set<T>().ToListAsync();
    }
}

public ICommand PageLoadedCommand{get；}
已加载页面上的专用异步无效（RoutedEventArgs args）
{
等待VendorsService.InitializeAsync（）；
BankItems=VendorsService.BankItems；
AuthorityItems=供应商服务.AuthorityItems；
VendorItems=VendorService.VendorItems；
}
公共ObservableCollection供应商项{get；set；}
公共ObservableCollection银行项目{get；set；}
公共ObservableCollection AuthorityItems{get；set；}

供应商服务

private TwoLinesService<BankEntity> BankService { get; } = new TwoLinesService<BankEntity>();
private TwoLinesService<AuthorityEntity> AuthorityService { get; } = new TwoLinesService<AuthorityEntity>();

public ObservableCollection<VendorModel> VendorItems { get; private set; }
public ObservableCollection<TwoLinesModel> BankItems { get; private set; }
public ObservableCollection<TwoLinesModel> AuthorityItems { get; private set; }

public async Task InitializeAsync()
{
    await BankService.InitializeAsync();
    await AuthorityService.InitializeAsync();

    VendorItems = new ObservableCollection<VendorModel>
    {
        new VendorModel { Name = "Name 1", Surname = "Surname 1", Patronymic = "MiddleName 1", IssueDate = new DateTime(2020, 2, 9) },
        new VendorModel { Name = "Name 2", Surname = "Surname 2", Patronymic = "MiddleName 2", IssueDate = new DateTime(2019, 3, 7) }
    };
    BankItems = BankService.Items;
    AuthorityItems = AuthorityService.Items;

    await Task.CompletedTask;
}

public class TwoLinesService<TEntity> 
    where TEntity : TwoLinesEntity, new()
{
    private IDataServiceFactory<TEntity> DataServiceFactory { get; } = new DataServiceFactory<TEntity>();
    public ObservableCollection<TwoLinesModel> Items { get; } = new ObservableCollection<TwoLinesModel>();

    public async Task InitializeAsync()
    {
        using var dataService = DataServiceFactory.Create();

        foreach (var entity in await dataService.SelectAll())
        {
            Items.Add(CreateModel(entity));
        }

        await Task.CompletedTask;
    }

    public TwoLinesModel CreateModel(TEntity source)
    {
        return new TwoLinesModel
        {
            ID = source.ID,
            Title = source.Title,
            Text = source.Text,
            CreatedOn = source.CreatedOn,
            LastModifiedOn = source.LastModifiedOn
        };
    }
}

private TwoLinesService银行服务{get；}=new TwoLinesService（）；
private TwoLinesService AuthorityService{get；}=new TwoLinesService（）；
公共可观测集合供应商项{get；private set；}
public observeCollection BankItems{get；private set；}
公共ObservableCollection AuthorityItems{get；private set；}
公共异步任务InitializeAsync（）
{
wait BankService.InitializeAsync（）；
等待AuthorityService.InitializeAsync（）；
VendorItems=新的可观察集合
{
新的供应商模型{Name=“Name 1”，姓氏=“Name 1”，赞助人=“MiddleName 1”，发布日期=新的日期时间（2020,2,9）}，
新供应商模型{Name=“Name 2”，姓氏=“Name 2”，赞助人=“MiddleName 2”，发布日期=新日期时间（2019,3,7）}
};
BankItems=BankService.Items；
AuthorityItems=AuthorityService.Items；
等待任务。完成任务；
}

TwoLinesService

private TwoLinesService<BankEntity> BankService { get; } = new TwoLinesService<BankEntity>();
private TwoLinesService<AuthorityEntity> AuthorityService { get; } = new TwoLinesService<AuthorityEntity>();

public ObservableCollection<VendorModel> VendorItems { get; private set; }
public ObservableCollection<TwoLinesModel> BankItems { get; private set; }
public ObservableCollection<TwoLinesModel> AuthorityItems { get; private set; }

public async Task InitializeAsync()
{
    await BankService.InitializeAsync();
    await AuthorityService.InitializeAsync();

    VendorItems = new ObservableCollection<VendorModel>
    {
        new VendorModel { Name = "Name 1", Surname = "Surname 1", Patronymic = "MiddleName 1", IssueDate = new DateTime(2020, 2, 9) },
        new VendorModel { Name = "Name 2", Surname = "Surname 2", Patronymic = "MiddleName 2", IssueDate = new DateTime(2019, 3, 7) }
    };
    BankItems = BankService.Items;
    AuthorityItems = AuthorityService.Items;

    await Task.CompletedTask;
}

public class TwoLinesService<TEntity> 
    where TEntity : TwoLinesEntity, new()
{
    private IDataServiceFactory<TEntity> DataServiceFactory { get; } = new DataServiceFactory<TEntity>();
    public ObservableCollection<TwoLinesModel> Items { get; } = new ObservableCollection<TwoLinesModel>();

    public async Task InitializeAsync()
    {
        using var dataService = DataServiceFactory.Create();

        foreach (var entity in await dataService.SelectAll())
        {
            Items.Add(CreateModel(entity));
        }

        await Task.CompletedTask;
    }

    public TwoLinesModel CreateModel(TEntity source)
    {
        return new TwoLinesModel
        {
            ID = source.ID,
            Title = source.Title,
            Text = source.Text,
            CreatedOn = source.CreatedOn,
            LastModifiedOn = source.LastModifiedOn
        };
    }
}

公共类TwoLinesService
其中tenty:twolencentity，new（）
{
私有IDataServiceFactory DataServiceFactory{get；}=new DataServiceFactory（）；
公共ObservableCollection项{get；}=new ObservableCollection（）；
公共异步任务InitializeAsync（）
{
使用var-dataService=dataservicecfactory.Create（）；
foreach（wait-dataService.SelectAll（）中的var实体）
{
添加（CreateModel（实体））；
}
等待任务。完成任务；
}
公共TwoLinesModel CreateModel（TEntity源）
{
返回新的TwoLinesModel
{
ID=source.ID，
Title=source.Title，
Text=source.Text，
CreatedOn=source.CreatedOn，
LastModifiedOn=source.LastModifiedOn
};
}
}

DataServiceFactory

public class DataServiceFactory<T> : IDataServiceFactory<T> where T : DomainEntity
{
    public IDataService<T> Create()
    {
        return Configuraiton.Current.DataProvider switch
        {
            DataProviderType.SQLite => new SQLiteService<T>(Configuraiton.Current.SQLiteConnectionString),
            _ => throw new NotImplementedException()
        };
    }
}

公共类DataServiceFactory:IDataServiceFactory其中T:DomainEntity
{
公共IDataService创建（）
{
返回Configurationon.Current.DataProvider开关
{
DataProviderType.SQLite=>新的SQLiteService（ConfigurationOn.Current.SQLiteConnectionString），
_=>抛出新的NotImplementedException（）
};
}
}

选择全部（）

公共部分类GenericDataService:IDataService其中T:DomainEntity
{
私有只读dbcontextu DbContext；
公共通用数据服务（DbContext DbContext）=>\u DbContext=DbContext；
公共异步任务SelectAll（）
{
返回wait_dbContext.Set（）.toListSync（）；
}
}
这可能是UWP异步编程中的常见陷阱。使用async/await/Task并不等同于在后台线程中运行代码。如果希望在后台线程中执行一些耗时的任务，则需要将其包装在task.Run（）中。否则UI线程将被阻止

请尝试使用Task.anyway中的SelectAll（）运行

public Task<IList<T>> SelectAll()
{
    return Task.Run(async ()=> { return await _dbContext.Set<T>().ToListAsync(); });
}

public任务SelectAll（）
{
return Task.Run（async（）=>{return await_dbContext.Set（）.ToListAsync（）；}）；
}
说明
我设法找到了瓶颈。该项目是开发的早期阶段。在启动期间，程序不会调用与数据库关联的方法。我在帮助下检测到第一次调用DataServiceFactory.Create（）时加载了新组件。在此之后，用户界面冻结立即结束

"ProgramName.exe" (CoreCLR: CoreCLR_UWP_Domain). Loaded "C:\Program Files\WindowsApps\Microsoft.NET.CoreFramework.Debug.2.2_2.2.27909.0_x64__8wekyb3d8bbwe\System.Threading.Tasks.Extensions.dll".
"ProgramName.exe" (CoreCLR: CoreCLR_UWP_Domain). Loaded "C:\Program Files\WindowsApps\Microsoft.NET.CoreFramework.Debug.2.2_2.2.27909.0_x64__8wekyb3d8bbwe\System.Linq.Expressions.dll".
"ProgramName.exe" (CoreCLR: CoreCLR_UWP_Domain). Loaded "C:\Program Files\WindowsApps\Microsoft.NET.CoreFramework.Debug.2.2_2.2.27909.0_x64__8wekyb3d8bbwe\System.Resources.ResourceManager.dll".
"ProgramName.exe" (CoreCLR: CoreCLR_UWP_Domain). Loaded "C:\Program Files\WindowsApps\Microsoft.NET.CoreFramework.Debug.2.2_2.2.27909.0_x64__8wekyb3d8bbwe\System.Diagnostics.Tracing.dll".
"ProgramName.exe" (CoreCLR: CoreCLR_UWP_Domain). Loaded "C:\Program Files\WindowsApps\Microsoft.NET.CoreFramework.Debug.2.2_2.2.27909.0_x64__8wekyb3d8bbwe\System.ComponentModel.TypeConverter.dll".
"ProgramName.exe" (CoreCLR: CoreCLR_UWP_Domain). Loaded "Anonymously Hosted DynamicMethods Assembly". 
"ProgramName.exe" (CoreCLR: CoreCLR_UWP_Domain). Loaded "C:\Program Files\WindowsApps\Microsoft.NET.CoreFramework.Debug.2.2_2.2.27909.0_x64__8wekyb3d8bbwe\System.Data.Common.dll".
"ProgramName.exe" (CoreCLR: CoreCLR_UWP_Domain). Loaded "C:\Program Files\WindowsApps\Microsoft.NET.CoreFramework.Debug.2.2_2.2.27909.0_x64__8wekyb3d8bbwe\System.ComponentModel.Primitives.dll".
"ProgramName.exe" (CoreCLR: CoreCLR_UWP_Domain). Loaded "C:\Program Files\WindowsApps\Microsoft.NET.CoreFramework.Debug.2.2_2.2.27909.0_x64__8wekyb3d8bbwe\System.Transactions.Local.dll".
"ProgramName.exe" (CoreCLR: CoreCLR_UWP_Domain). Loaded "C:\Program Files\WindowsApps\Microsoft.NET.CoreFramework.Debug.2.2_2.2.27909.0_x64__8wekyb3d8bbwe\System.ComponentModel.Annotations.dll".
"ProgramName.exe" (CoreCLR: CoreCLR_UWP_Domain). Loaded "C:\Program Files\WindowsApps\Microsoft.NET.CoreFramework.Debug.2.2_2.2.27909.0_x64__8wekyb3d8bbwe\System.Threading.Timer.dll".
"ProgramName.exe" (CoreCLR: CoreCLR_UWP_Domain). Loaded "C:\Program Files\WindowsApps\Microsoft.NET.CoreFramework.Debug.2.2_2.2.27909.0_x64__8wekyb3d8bbwe\System.Threading.Thread.dll".
"ProgramName.exe" (CoreCLR: CoreCLR_UWP_Domain). Loaded "C:\Program Files\WindowsApps\Microsoft.NET.CoreFramework.Debug.2.2_2.2.27909.0_x64__8wekyb3d8bbwe\System.Text.RegularExpressions.dll".
"ProgramName.exe" (CoreCLR: CoreCLR_UWP_Domain). Loaded "C:\Program Files\WindowsApps\Microsoft.NET.CoreFramework.Debug.2.2_2.2.27909.0_x64__8wekyb3d8bbwe\System.Buffers.dll".
"ProgramName.exe" (CoreCLR: CoreCLR_UWP_Domain). Loaded "C:\Program Files\WindowsApps\Microsoft.NET.CoreFramework.Debug.2.2_2.2.27909.0_x64__8wekyb3d8bbwe\System.Memory.dll".

解决方案
主要的解决方案是在启动时加载数据。在这个阶段，没有要加载的内容

我找到两个临时解决办法


在
App.xaml.cs
中调用工厂创建。这将加载大多数组件

DataServiceFactory.Create（）
和
dataService.SelectAll（）
中的内容。你有什么理由叫它两次，或者那只是一个打字错误吗？@Euphoric是的，就是打字错误。我添加了代码。