Question

如何访问const或属性上的Description属性，即

public static class Group
{

    [Description( "Specified parent-child relationship already exists." )]
    public const int ParentChildRelationshipExists = 1;

    [Description( "User is already a member of the group." )]
    public const int UserExistsInGroup = 2;

}

或

public static class Group
{

    [Description( "Specified parent-child relationship already exists." )]
    public static int ParentChildRelationshipExists { 
      get { return 1; } 
    }

    [Description( "User is already a member of the group." )]
    public static int UserExistsInGroup { 
      get { return 2; } 
    }

}

在调用类中，我想访问Description属性，即

int x = Group.UserExistsInGroup;
string description = Group.UserExistsInGroup.GetDescription(); // or similar

我也对其他方法的想法持开放态度。

修改我应该提到我在这里看到了一个例子： Do auto-implemented properties support attributes?

但是，我正在寻找一种方法来访问description属性，而不必在属性类型中输入字符串文字，即，我宁愿不这样做：

typeof(Group).GetProperty("UserExistsInGroup");

扩展方法的某些内容;类似于以下方法，它将通过扩展方法返回Enum上的Description属性：

public static String GetEnumDescription( this Enum obj )
{
    try
    {
        System.Reflection.FieldInfo fieldInfo = 
            obj.GetType().GetField( obj.ToString() );

        object[] attribArray = fieldInfo.GetCustomAttributes( false );

        if (attribArray.Length > 0)
        {
            var attrib = attribArray[0] as DescriptionAttribute;

            if( attrib != null  )
                return attrib.Description;
        }
        return obj.ToString();
    }
    catch( NullReferenceException ex )
    {
        return "Unknown";
    }
}

Answer 1

尝试以下

var property = typeof(Group).GetProperty("UserExistsInGroup");
var attribute = property.GetCustomAttributes(typeof(DescriptionAttribute), true)[0];
var description = (DescriptionAttribute)attribute;
var text = description.Description;

Answer 2

您可以致电MemberInfo.GetCustomAttributes()以获取Type成员上定义的所有自定义属性。您可以通过以下操作获取该属性的MemberInfo：

PropertyInfo prop = typeof(Group).GetProperty("UserExistsInGroup",
    BindingFlags.Public | BindingFlags.Static);

Answer 3

好的，我已经看过你的编辑了，我不确定你能用扩展方法做到这一点，因为他们会知道包含类的类型。

这听起来有些古怪，但是如何创建一个新的类“DescribedInt”，它会有一个隐式的强制转换操作符让你自动将它用作int？你几乎可以使用你描述的方式。你仍然会有一个描述，但是当你需要像Int一样使用它时，你不需要获得.Data属性......

例如：

private void ExampleUse()
{
    int myvalue = Group.A; //see, no need to cast or say ".Data" - implicit cast
    string text = Group.A.Description;

//用值来做事...... }

public static class Group
{
    public static DescribedInt A = new DescribedInt(12, "some description");
    public static DescribedInt B = new DescribedInt(88, "another description");
}

public class DescribedInt
{
    public readonly int data;
    public readonly string Description;

    public DescribedInt(int data, string description)
    {
        this.data = data;
        this.Description = description;
    }

    //automatic cast to int
    public static implicit operator int(DescribedInt orig)
    {
        return orig.data;
    }

    //public DescribedInt(string description)
    //{
    //    this.description = description;
    //}

    //if you ever need to go the "other way"
    //public static implicit operator DescribedInt(int orig)
    //{
    //    return new DescribedInt(orig, "");
    //}
}

Answer 4

这是我用来处理.NET中的自定义属性的辅助类

public class AttributeList : List<Attribute>
{
    /// <summary>
    /// Gets a list of custom attributes
    /// </summary>
    /// <param name="propertyInfo"></param>
    /// <returns></returns>
    public static AttributeList GetCustomAttributeList(ICustomAttributeProvider propertyInfo)
    {
        var result = new AttributeList();
        result.AddRange(propertyInfo.GetCustomAttributes(false).Cast<Attribute>());
        return result;
    }

    /// <summary>
    /// Finds attribute in collection by its type
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <returns></returns>
    public T FindAttribute<T>() where T : Attribute
    {
        return (T)Find(x => typeof(T).IsAssignableFrom(x.GetType()));
    }

    public bool IsAttributeSet<T>() where T : Attribute
    {
        return FindAttribute<T>() != null;
    }
}

还为MsTest进行单元测试，显示如何使用此类

[TestClass]
public class AttributeListTest
{
    private class TestAttrAttribute : Attribute
    {
    }

    [TestAttr]
    private class TestClass
    {
    }

    [TestMethod]
    public void Test()
    {
        var attributeList = AttributeList.GetCustomAttributeList(typeof (TestClass));
        Assert.IsTrue(attributeList.IsAttributeSet<TestAttrAttribute>());
        Assert.IsFalse(attributeList.IsAttributeSet<TestClassAttribute>());
        Assert.IsInstanceOfType(attributeList.FindAttribute<TestAttrAttribute>(), typeof(TestAttrAttribute));
    }
}

http://www.kozlenko.info/2010/02/02/getting-a-list-of-custom-attributes-in-net/

如何在C＃中的属性或const上访问Description属性？

4 个答案: