绑定到EF模型时，转换器显示System.Data.Entity.DynamicProxies [英] Converter shows System.Data.Entity.DynamicProxies when bind to EF Model
问题描述
我正在编写WPF MVVM应用程序.我正在尝试使用转换器在组合框中显示联系人姓名.我不认为我可以使用DisplayMemberPath，因为全名"列不存在.
I am writing a WPF MVVM Application. I am trying to use a converter to display a contact name in the combobox. I do not think I can use the DisplayMemberPath since a "fullname" column does not exist.
使用Entity Framework将ComboBox绑定到一个类中的一个类.给出以下内容:
The ComboBox is being bound to a class within a class using Entity Framework. Given the following:
.cs文件
public class Car
{
public int CarId { get; set; }
public string Make { get; set; }
public string Model { get; set; }
public string Year { get; set; }
public Contact Owner { get; set; }
}
public class Contact
{
public int ContactID { get; set; }
public string Salutation { get; set; }
public string FirstName { get; set; }
public string MiddleName { get; set; }
public string LastName { get; set; }
public string Suffix { get; set; }
}
public class MultiBindingConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
string name = "";
if (!(values[0] is Contact Contact))
return name;
switch ((string)parameter)
{
case "LastNameFirst":
name += (!string.IsNullOrEmpty(Contact.LastName)) ? Contact.LastName : "";
name += (!string.IsNullOrEmpty(Contact.Suffix)) ? " " + Contact.Suffix : "";
name += (!string.IsNullOrEmpty(Contact.FirstName)) ? ", " + Contact.FirstName : "";
name += (!string.IsNullOrEmpty(Contact.MiddleName)) ? " " + Contact.MiddleName : "";
name += (!string.IsNullOrEmpty(Contact.Salutation)) ? ", " + Contact.Salutation : "";
break;
case "FormatNormal":
default:
name += (!string.IsNullOrEmpty(Contact.Salutation)) ? Contact.Salutation : "";
name += (!string.IsNullOrEmpty(Contact.FirstName)) ? " " + Contact.FirstName : "";
name += (!string.IsNullOrEmpty(Contact.MiddleName)) ? " " + Contact.MiddleName : "";
name += (!string.IsNullOrEmpty(Contact.LastName)) ? " " + Contact.LastName : "";
name += (!string.IsNullOrEmpty(Contact.Suffix)) ? " " + Contact.Suffix : "";
break;
}
return name;
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
.XAML文件
<UserControl.Resources>
<local:MultiBindingConverter x:Key="MBC" />
</UserControl.Resources>
<ComboBox ItemsSource="{Binding Contacts, Mode=OneTime}" // Contacts is a full list of the Contact Class (so its every Owner)
SelectedValuePath="ContactId"
SelectedValue="{Binding Car.Owner.ContactId, Mode=TwoWay}"
>
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock>
<TextBlock.Text>
<MultiBinding Converter="{StaticResource MBC}" ConverterParameter="LastNameFirst" >
<Binding Path="Contacts"/>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
问题在于ComboBox中显示的最终结果是:
The issue is that the end result that is displayed in the ComboBox is:
System.Data.Entity.DynamicProxies.Contact _.......
System.Data.Entity.DynamicProxies.Contact_.......
它没有以正确的格式显示所有者名称.我如何以这种方式绑定到ComboBox以获得我想要的输出(即，Doe Sr.，John Michael，先生)
It is not showing the Owner name in the correct format. How can I do a binding to the ComboBox in this manner to get the output I desire (ie. Doe Sr., John Michael, Mr.)
EDIT 我也尝试过这种方式
EDIT I have also tried it this way
.cs IValueConverter
.cs IValueConverter
public class ContactNameConverter : BaseValueConverter<ContactNameConverter>
{
public override object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
string name = "";
if (!(value is Contact Contact))
return name;
switch ((string)parameter)
{
case "LastNameFirst":
name += (!string.IsNullOrEmpty(Contact.LastName)) ? Contact.LastName : "";
name += (!string.IsNullOrEmpty(Contact.Suffix)) ? " " + Contact.Suffix : "";
name += (!string.IsNullOrEmpty(Contact.FirstName)) ? ", " + Contact.FirstName : "";
name += (!string.IsNullOrEmpty(Contact.MiddleName)) ? " " + Contact.MiddleName : "";
name += (!string.IsNullOrEmpty(Contact.Salutation)) ? ", " + Contact.Salutation : "";
break;
case "FormatNormal":
default:
name += (!string.IsNullOrEmpty(Contact.Salutation)) ? Contact.Salutation : "";
name += (!string.IsNullOrEmpty(Contact.FirstName)) ? " " + Contact.FirstName : "";
name += (!string.IsNullOrEmpty(Contact.MiddleName)) ? " " + Contact.MiddleName : "";
name += (!string.IsNullOrEmpty(Contact.LastName)) ? " " + Contact.LastName : "";
name += (!string.IsNullOrEmpty(Contact.Suffix)) ? " " + Contact.Suffix : "";
break;
}
return name;
}
public override object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
.XAML
<ComboBox ItemsSource="{Binding Contacts, Mode=OneTime}"
SelectedValuePath="ContactId"
SelectedValue="{Binding Car.Owner.ContactId, Mode=TwoWay}"
>
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Path=., Converter={local:ContactNameConverter}}"/>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
推荐答案
EF将 System.Data.Entity.DynamicProxies 类型用作启用延迟加载的代理.您可以通过将 ObjectContext.ContextOptions.ProxyCreationEnabled 设置为false来禁用代理创建.链接
The type System.Data.Entity.DynamicProxies is used by EF as a proxy to enable lazy loading. You can disable proxy creation by setting ObjectContext.ContextOptions.ProxyCreationEnabled to false. link
但是，建议使用ViewModels而不是EF模型作为绑定源.
However, it is recommended to use ViewModels as the source of the binding instead of EF Models.
您还可以将新属性添加到EF模型(最好是添加到VM)作为每个项目的绑定源:
You can also add a new property to an EF Model (or preferably to a VM) as the source of the bindings of each item:
[NotMapped]
public string FirstLastName { get { return FirstName + ", " + LastName; } }
您应该记住， ItemTemplate 的 DataContext 引用了集合的每个元素.因此，类型为 Contact 的对象的路径为.不是 Contacts .
You should keep in mind that DataContext of ItemTemplate refers to each element of a collection. So the path of an object of type Contact is . not Contacts.
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock>
<TextBlock.Text>
<MultiBinding Converter="{StaticResource MBC}" ConverterParameter="LastNameFirst" >
<Binding Path="."/>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</DataTemplate>
</ComboBox.ItemTemplate>
我还注意到您使用了一个带有一个值的多值转换器.您可以按照以下方式进行操作:
I also noticed that you used a multi value converter with one value. You could do it like the following:
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock>
<TextBlock.Text>
<MultiBinding Converter="{StaticResource MBC}" ConverterParameter="LastNameFirst" >
<Binding Path="FirstName"/>
<Binding Path="LastName"/>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</DataTemplate>
</ComboBox.ItemTemplate>
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
if(parameter == "LastNameFirst")
return string.Format("{0}, {1}", values[0], values[1]);
else
return string.Format("{0}, {1}", values[1], values[0]);
}
这篇关于绑定到EF模型时，转换器显示System.Data.Entity.DynamicProxies的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
