小编Edu*_*tes的帖子

我试图在一个新项目中运行命令'Enable-Migrations',我收到了消息:

PM> Enable-Migrations
The term 'Enable-Migrations' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verif
y that the path is correct and try again.
At line:1 char:18
+ Enable-Migrations <<<< 
    + CategoryInfo          : ObjectNotFound: (Enable-Migrations:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

但是在所有其他项目中,命令运行得很好.

为什么会这样？

顺便说一下,我正在使用VS2010 Professional SP1

编辑:我重新安装了命令:Install-Package EntityFramework -IncludePrerelease ,问题消失了.

我有一个Combobox,其ItemsSource是一个ObservableCollection的int值.我的组合框项目模板包含一个图像和一个文本块,其内容由2个转换器给出.

如何设置这2个绑定？以下代码无法编译:

<ComboBox.ItemTemplate>
     <DataTemplate>
          <StackPanel Orientation="Horizontal">
               <Image Source="{Binding, Converter={StaticResource IntToImageConverter}}" Stretch="None" />
               <TextBlock Text="{Binding, Converter={StaticResource IntToStringConverter}}" />
          </StackPanel>
     </DataTemplate>
</ComboBox.ItemTemplate>

令我惊讶的是,使用CreateDatabaseIfNotExists上下文初始化程序,该行

context.Database.Initialize(true)

如果架构与我的代码第一个架构不匹配,则不会抛出异常.

有没有办法验证当前数据库是否与我们的模式匹配,例如,我们尝试访问一个实体,其表不再存在于数据库中,并且EF抛出异常？

如果我在EF中定义了多对多关系:

public class StudentImage 
{
    public int StudentId { get; set; }
    public int ImageId { get; set; }
    public int Order { get; set; }
    public virtual Student Student { get; set; }
    public virtual Image Image { get; set; }
}

public class Student
{
    public int Id { get; set; }
    public string Name { get; set; }
    public virtual ICollection<StudentImage> Images { get; set; }
}


public class Image
{
    public int Id { get; set; …

我有一个名为UniqueNameSolidWoodRule的精简版ValidationRule来验证数据网格中的重复条目.

这是代码:

public class UniqueNameSolidWoodRule : ValidationRule
{
    public CollectionViewSource CurrentCollection { get; set; }

    public override ValidationResult Validate(object value, CultureInfo cultureInfo)
    {
        if (value != null)
        {
            ObservableCollection<SolidWood_VM> castedCollection = (ObservableCollection<SolidWood_VM>)CurrentCollection.Source;

            foreach (SolidWood_VM swVM in castedCollection)
            {
                if (swVM.Designation == value.ToString())
                {
                    return new ValidationResult(false, ResourcesManager.Instance.GetString("DuplicatedRecord"));
                }
            }
        }

        return new ValidationResult(true, null);
    }
}

这是XAML片段:

<DataGrid.Resources>
        <CollectionViewSource x:Key="CurrentSolidWoodCollection" Source="{Binding Path=SolidWoods}" />
</DataGrid.Resources>

 <DataGridTextColumn x:Name="Column2" Header="{x:Static p:Resources.Designation}" Width="auto">
        <DataGridTextColumn.Binding>
            <Binding Path="Designation" ValidatesOnDataErrors="True" UpdateSourceTrigger="LostFocus">
                 <Binding.ValidationRules>
                        <my:UniqueNameSolidWoodRule  CurrentCollection="{StaticResource CurrentSolidWoodCollection}"/>
                  </Binding.ValidationRules>
             </Binding> …

想象一下,我有一个名为"MyCheckBoxStyle"的CheckBox自定义样式.

如何根据MyCheckBoxStyle创建嵌入自定义DataGridCheckBoxColumn样式的Datagrid样式？

想象一下,我有这张桌子:

Column A | Column B | Column C
------------------------------
   111         X        10
   111         Y        12

如何查询此表以显示如下结果:

Column A |     X     |      Y
-----------------------------------
   111         10           12

如果我将DataTrigger放在一个简单的Listbox中,我会得到这个运行时异常:

在使用ItemsSource之前,项集合必须为空

我没有datatrigger的列表框(没有例外):

<ListBox ItemsSource="{Binding EdgedBoards}" SelectedItem="{Binding SelEdgedBoard, Mode=TwoWay}" DisplayMemberPath="Name">
    <ListBox.ItemContainerStyle>
        <Style TargetType="{x:Type ListBoxItem}" 
               BasedOn="{StaticResource {x:Type ListBoxItem}}">

            <Setter Property="IsSelected"
                    Value="{Binding IsSelected, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
        </Style>
    </ListBox.ItemContainerStyle>
</ListBox>

我的ListBox包含DataTrigger:

<ListBox ItemsSource="{Binding EdgedBoards}" SelectedItem="{Binding SelEdgedBoard, Mode=TwoWay}" DisplayMemberPath="Name">
    <Style TargetType="{x:Type ListBox}" BasedOn="{StaticResource {x:Type ListBox}}">
        <Setter Property="Focusable" Value="True" />

        <Style.Triggers>
            <DataTrigger Binding="{Binding ElementName=EdgedBoardsAdd_UC, Path=Visibility}" Value="Visible">
                <Setter Property="Focusable" Value="False" />
            </DataTrigger>
        </Style.Triggers>
    </Style>

    <ListBox.ItemContainerStyle>
        <Style TargetType="{x:Type ListBoxItem}" BasedOn="{StaticResource {x:Type ListBoxItem}}">
            <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
        </Style>
    </ListBox.ItemContainerStyle>
</ListBox>

后一个代码有什么问题？