定义自定义属性类以使属性在某些情况下可浏览

Question

我的项目中有一些类，某些属性Browsable(false)，因此用户看不到它们：

public class OrderEntity{
public int Id { get; set;}   
[Browsable(false)]
public int ProductId { get; set;}   
....
}

我想，如果最终用户是管理员，他可以看到ProductId，但另一个用户看不到它。

所以我需要这样的东西：

public class OrderEntity{
public int Id { get; set;}   
[CustomizedBrowsable(false)]
public int ProductId { get; set;}   
....
}

public class CustomizedBrowsable: Attribute
{
if(AppContext.UserCode == "Admin") // The current user code saved in a static variable AppContext.UserCode.
//do somethings   
else
//do somethings else 
}

Answer 1

这不是您可以通过属性执行的操作，因为BrowsableAttribute是sealed。要通过绑定执行此操作，您需要一个自定义类型描述符 - 因此您需要在类型上实现ICustomTypeDescriptor(直接或通过TypeDescriptionProvider(，提供自定义PropertyDescriptor，并更改在那里定义可浏览性的方式(IsBrowsable，IIRC(。

这是大量的工作。

坦率地说，在几乎所有情况下，最好只手动控制绑定，并且仅在检查安全级别后添加列/输入/任何内容。

Answer 2

我使用类代码定义了自己的AdminBrowsable类Browsable：

[AttributeUsage(AttributeTargets.All)]
public sealed class AdminBrowsableAttribute : Attribute
{
/// <summary>
/// Specifies that a property or event can be modified at design time. This static field is read-only.
/// </summary>
public static readonly AdminBrowsableAttribute Yes = new AdminBrowsableAttribute(true);
/// <summary>
/// Specifies that a property or event cannot be modified at design time. This static field is read-only.
/// </summary>
public static readonly AdminBrowsableAttribute No = new AdminBrowsableAttribute(false);
/// <summary>
/// Specifies the default value for the <see cref="T:System.ComponentModel.BrowsableAttribute"/>, which is <see cref="F:System.ComponentModel.BrowsableAttribute.Yes"/>. This static field is read-only.
/// </summary>
public static readonly AdminBrowsableAttribute Default = AdminBrowsableAttribute.Yes;
private bool browsable = true;
/// <summary>
/// Gets a value indicating whether an object is browsable.
/// </summary>
/// 
/// <returns>
/// true if the object is browsable; otherwise, false.
/// </returns>
public bool Browsable
{
get
{
return this.browsable;
}
}
/// <summary>
/// Initializes a new instance of the <see cref="T:System.ComponentModel.BrowsableAttribute"/> class.
/// </summary>
/// <param name="browsable">true if a property or event can be modified at design time; otherwise, false. The default is true. </param>
public AdminBrowsableAttribute(bool browsable)
{
if (!AppContext.IsAdmin)
{
this.browsable = browsable;
}
}
/// <summary>
/// Indicates whether this instance and a specified object are equal.
/// </summary>
/// 
/// <returns>
/// true if <paramref name="obj"/> is equal to this instance; otherwise, false.
/// </returns>
/// <param name="obj">Another object to compare to. </param>
public override bool Equals(object obj)
{
if (obj == this)
return true;
AdminBrowsableAttribute browsableAttribute = obj as AdminBrowsableAttribute;
if (browsableAttribute != null)
return browsableAttribute.Browsable == this.browsable;
return false;
}
/// <summary>
/// Returns the hash code for this instance.
/// </summary>
/// 
/// <returns>
/// A 32-bit signed integer hash code.
/// </returns>
public override int GetHashCode()
{
return this.browsable.GetHashCode();
}
/// <summary>
/// Determines if this attribute is the default.
/// </summary>
/// 
/// <returns>
/// true if the attribute is the default value for this attribute class; otherwise, false.
/// </returns>
public override bool IsDefaultAttribute()
{
return this.Equals((object)AdminBrowsableAttribute.Default);
}
}

我只更改了Constructor：

public AdminBrowsableAttribute(bool browsable)
{
if (AppContext.UserCode != "Admin")
{
this.browsable = browsable;
}
}