Question

我使用MVVM - WPF Browser Application创建了Entity Framework 6个应用程序。我试图删除dataGrid中的一行。我可以删除一行，但是当我尝试删除一行时，我有以下错误：

System.Runtime.Serialization.SerializationException：无法找到 assembly＆＃39; EntityFramework，Version = 6.0.0.0，Culture = neutral，公钥= XXX＆＃39;

的 ViewModelBase：

public class CommandBase<T> : INotifyPropertyChanged
{
    #region "INotifyPropertyChanged members"
    public event PropertyChangedEventHandler PropertyChanged;
    //This routine is called each time a property value has been set. 
    //This will //cause an event to notify WPF via data-binding that a change has occurred. 
    protected void OnPropertyChanged(string propertyName)
    {
        var handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    #endregion
    private ObservableCollection<T> collection;
    public ObservableCollection<T> Collection
    {
        get
        {
            if (collection == null)
            {
                Get();
            }
            return collection;
        }
        set { collection = value;
            OnPropertyChanged("Collection"); }
    }
    private T _selected;
    public T Selected
    {
        get { return _selected; }
        set { _selected = value; 
            OnPropertyChanged("Selected"); }
    }
    private ICommand getCommand;
    private ICommand saveCommand;
    private ICommand removeCommand;
    public ICommand GetCommand
    {
        get
        {
            return getCommand ?? (getCommand = new RelayCommand(Get,CanGet));
        }
    }
    protected virtual bool CanGet()
    {
        return true;
    }
    protected virtual void Get()
    {
        //return true;
    }
    public ICommand SaveCommand
    {
       get
       {
            return saveCommand ?? (saveCommand = new RelayCommand(Save, CanSave));
       }
    }
    protected virtual void Save()
    {
        //return true;
    }
    protected virtual bool CanSave()
    {
        return true;
    }
    public ICommand DeleteCommand
    {
        get
        {
            return removeCommand ?? (removeCommand = new RelayCommand(Delete,CanDelete));
        }
    }
    protected virtual void Delete()
    {
    }
    protected virtual bool CanDelete()
    {
         if (Selected != null)
            return true;
        else
            return false;
    }
}

的视图模型：

public class SupplierViewModel : CommandBase<foodSupplier>
{
    public Context ctx = new Context();
    protected override void Get()
    {
        ctx.foodSuppliers.ToList().ForEach(supplier => ctx.foodSuppliers.Local.Add(supplier));
        Collection = ctx.foodSuppliers.Local;
    }
    protected override bool CanGet()
    {
        return true;
    }
    protected override void Save()
    {
        foreach (foodSupplier item in Collection)
        {
            if (ctx.Entry(item).State == System.Data.Entity.EntityState.Added)
            {
                ctx.foodSuppliers.Add(item);
            }
        }
        ctx.SaveChanges();
    }
    protected override void Delete()
    {
        var id = Selected;
        var supp = (from s in ctx.foodSuppliers
                where s.idfoodSupplier == id.idfoodSupplier
                select s).SingleOrDefault();
        ctx.foodSuppliers.Remove(supp);
        ctx.SaveChanges();
        Collection.Remove(supp);
    }
    protected virtual bool CanDelete()
    {
        return true;
    }
}

查看：

<DataGrid x:Name="dataGrid"
          Margin="5"
          ItemsSource="{Binding Collection}"
          AutoGenerateColumns="False"
          SelectedItem="{Binding Selected, Mode=TwoWay}"
          SelectionMode="Extended"
          SelectionUnit="FullRow">
    <DataGrid.Columns>
        <DataGridTextColumn x:Name="dataGridTextColumn"
                            Header="Supplier"
                            Binding="{Binding idfoodSupplier, UpdateSourceTrigger=PropertyChanged}"
                            Visibility="Hidden" />
        <DataGridTextColumn Header="Supplier"
                            Binding="{Binding supplier, UpdateSourceTrigger=PropertyChanged}" />
    </DataGrid.Columns>
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="Loaded">
            <i:InvokeCommandAction Command="{Binding GetCommand}" />
        </i:EventTrigger>
    </i:Interaction.Triggers>
</DataGrid>
<Button Height="Auto"
        Width="Auto"
        Content="Delete"
        Command="{Binding DeleteCommand}" />

的 App.config中：

    <configSections>
        <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
        <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
      </configSections>
      <entityFramework>
        <defaultConnectionFactory type="MySql.Data.Entity.MySqlConnectionFactory, MySql.Data.Entity.EF6" />
        <providers>
          <provider invariantName="MySql.Data.MySqlClient" type="MySql.Data.MySqlClient.MySqlProviderServices, MySql.Data.Entity.EF6" />
        </providers>
      </entityFramework>
 <connectionStrings>
    <add name="xx" connectionString="xxx" providerName="System.Data.EntityClient" />
  </connectionStrings>
</configuration>

Answer 1

我已经对您的代码进行了全面测试，并且可以正常删除所有5行，甚至是最后一行。

您的代码需要先选择一行，确保在DataGrid中选择一行，然后删除该行。只有当用户在DataGrid中选择一行时，您才可以禁用命令按钮并启用它。

我对您的代码进行了以下更改：

public ICommand GetCommand
        {
            get
            {
                return getCommand ?? (getCommand = new RelayCommand(p=>this.Get(), p=>this.CanGet()));
            }
        }

在其他命令中也是如此：

return saveCommand ?? (saveCommand = new RelayCommand(p=>this.Save(), p=>this.CanSave()));

并在

return removeCommand ?? (removeCommand = new RelayCommand(p=>this.Delete(), p=>this.CanDelete()));

第二个解决方案可能是：

打开

工具＆gt; Nuget包管理器＆gt;包管理器控制台

然后运行

install-package entityframework -version 6.0.0.0

尝试在此处发布的解决方案：

Why is Entity Framework 6.1.3 throwing a "Could not load type 'System.Data.Entity.Infrastructure.TableExistenceChecker'"

Answer 2

我发现这个问题是在随机背景下发生的。例如，昨天我运行了Windows Update并安装了27个额外的更新。第二天，这个错误开始每15分钟左右抛出一次。正在运行的软件没有改变。

似乎Windows更新正在等待挂起的重启。确保服务器很满意，这个错误就消失了......

System.Runtime.Serialization.SerializationException：无法找到程序集＆＃39; EntityFramework，Version = 6.0.0.0，Culture = neutral，PublicKeyToken = xxx＆＃39;

的 ViewModelBase：

的视图模型：

查看：

的 App.config中：

2 个答案: