如何将我的属性添加到代码生成的Linq2Sql类属性？

我想为Linq 2 Sql类属性添加属性.例如,此列可以在UI中使用,也可以在UI中自读,目前为止.

我考虑过使用模板,有谁知道如何使用它？还是别的什么？

一般来说,您是否会使用代码生成的类来解决这个问题？

1> Jason Wicker..：

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您可以利用System.ComponentModel.DataAnnotations中的新元数据功能,这将允许我们将MetaData与现有域模型分开.

例如:

[MetadataType (typeof (BookingMetadata))]
public partial class Booking
{
 // This is your custom partial class     
}

public class BookingMetadata
{
 [Required] [StringLength(15)]
 public object ClientName { get; set; }

 [Range(1, 20)]
 public object NumberOfGuests { get; set; }

 [Required] [DataType(DataType.Date)]
 public object ArrivalDate { get; set; }
}

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注意:MetadataClass中的属性实际上并未直接添加到目标类.例如,如果您在Booking.ClientName上运行MemberInfo.IsDefined()以查找Required属性,则无法找到它.看来,使用MetadataType应用属性的库必须在目标类上查找类级MetadataType属性,如果找到,则在元类中搜索任何相关属性.我很失望,我无法定义自定义属性,使用MetadataType应用它们,并使用Member.IsDefined()检测它们.为此,我认为你需要Marc的解决方案.

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我认为这是**使用的解决方案.

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是的,这是炸弹 - 很棒的答案!

2> Marc Gravell..：

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根据要求,这是一种使用a CustomTypeDescriptor在运行时编辑属性的方法; 这里的例子是win-forms,但将它交换到WPF以查看它是否有效应该非常简单......

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Windows.Forms;
// example POCO
class Foo {
    static Foo()
    {   // initializes the custom provider (the attribute-based approach doesn't allow
        // access to the original provider)
        TypeDescriptionProvider basic = TypeDescriptor.GetProvider(typeof(Foo));
        FooTypeDescriptionProvider custom = new FooTypeDescriptionProvider(basic);
        TypeDescriptor.AddProvider(custom, typeof(Foo));
    }
    public string Name { get; set; }
    public DateTime DateOfBirth { get; set; }
}
// example form
static class Program {
    [STAThread]
    static void Main() {
        Application.EnableVisualStyles();
        Application.Run( new Form {
                Controls = {
                    new DataGridView {
                        Dock = DockStyle.Fill,
                        DataSource = new BindingList {
                            new Foo { Name = "Fred", DateOfBirth = DateTime.Today.AddYears(-20) }
                        }
                    }
                }
            });
    }
}

class FooTypeDescriptionProvider : TypeDescriptionProvider
{
    ICustomTypeDescriptor descriptor;
    public FooTypeDescriptionProvider(TypeDescriptionProvider parent) : base(parent) { }
    public override ICustomTypeDescriptor GetTypeDescriptor(Type objectType, object instance)
    {   // swap regular descriptor for bespoke (Foo) descriptor
        if (descriptor == null)
        {
            ICustomTypeDescriptor desc = base.GetTypeDescriptor(typeof(Foo), null);
            descriptor = new FooTypeDescriptor(desc);
        }
        return descriptor;
    }
}
class FooTypeDescriptor : CustomTypeDescriptor
{
    internal FooTypeDescriptor(ICustomTypeDescriptor parent) : base(parent) { }
    public override PropertyDescriptorCollection GetProperties()
    {   // wrap the properties
        return Wrap(base.GetProperties());
    }
    public override PropertyDescriptorCollection GetProperties(Attribute[] attributes)
    {   // wrap the properties
        return Wrap(base.GetProperties(attributes));
    }

    static PropertyDescriptorCollection Wrap(PropertyDescriptorCollection properties)
    {
        // here's where we have an opportunity to swap/add/remove properties
        // at runtime; we'll swap them for pass-thru properties with
        // edited atttibutes
        List list = new List(properties.Count);
        foreach (PropertyDescriptor prop in properties)
        {
            // add custom attributes here...
            string displayName = prop.DisplayName;
            if (string.IsNullOrEmpty(displayName)) displayName = prop.Name;

            list.Add(new ChainedPropertyDescriptor(prop, new DisplayNameAttribute("Foo:" + displayName)));
        }
        return new PropertyDescriptorCollection(list.ToArray(), true);
    }
}


class ChainedPropertyDescriptor : PropertyDescriptor
{
    // this passes all requests through to the underlying (parent)
    // descriptor, but has custom attributes etc;
    // we could also override properties here...
    private readonly PropertyDescriptor parent;
    public ChainedPropertyDescriptor(PropertyDescriptor parent, params Attribute[] attributes)
        : base(parent, attributes)
    {
        this.parent = parent;
    }
    public override bool ShouldSerializeValue(object component) { return parent.ShouldSerializeValue(component); }
    public override void SetValue(object component, object value) { parent.SetValue(component, value); }
    public override object GetValue(object component) { return parent.GetValue(component); }
    public override void ResetValue(object component) { parent.ResetValue(component); }
    public override Type PropertyType {get { return parent.PropertyType; } }
    public override bool IsReadOnly { get { return parent.IsReadOnly; } }
    public override bool CanResetValue(object component) {return parent.CanResetValue(component);}
    public override Type ComponentType { get { return parent.ComponentType; } }
    public override void AddValueChanged(object component, EventHandler handler) {parent.AddValueChanged(component, handler);  }
    public override void RemoveValueChanged(object component, EventHandler handler) { parent.RemoveValueChanged(component, handler); }
    public override bool SupportsChangeEvents { get { return parent.SupportsChangeEvents; } }
}