从属性值获取属性

本文关键字：属性 获取 从属性 | 更新日期: 2023-09-27 18:25:21

拥有这个简单的类：

public class Book
{
    [DataMember]
    [Column("Bok_Name")]
    [Author("AuthorName")]
    public string Name{ get; set; }
    [DataMember]
    [Column("Bok_Publisher")]
    public string Publisher{ get; set; }
}

在知道属性类型为Column且值为Bok_Name的情况下，如何从属性中获取PropertyInfo。我尝试使用linq查询来完成此操作。

从属性值获取属性

使用反射和.NET扩展CustomAttributeExtensions.GetCustomAttribute｛T｝方法，可以找到具有自定义属性的属性。在这种情况下，自定义属性来自System.ComponentModel.DataAnnotations.Schema.ColumnAttribute。

var book = new Book { Name = "Jitterbug Perfume" };
PropertyInfo bokName = typeof(Book)
    .GetProperties(BindingFlags.Public | BindingFlags.Instance) // add other bindings if needed
    .FirstOrDefault(x => x.GetCustomAttribute<ColumnAttribute>() != null
       && x.GetCustomAttribute<ColumnAttribute>().Name.Equals("Bok_Name", StringComparison.OrdinalIgnoreCase));
// the above query only gets the first property with Column attribute equal to "Bok_Name"
// if there are more than one, then use a .Where clause instead of FirstOrDefault.
if (bokName != null)
{
    string name = bokName.GetValue(book).ToString();
    // do other stuff
}

    var type = typeof (Book); //or var type=instance.GetType();
    var res=type.GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic)
        .Where(
            p =>
                (p.GetCustomAttribute<ColumnAttribute>() ?? new ColumnAttribute()).Value == "Bok_Name");

在存钱罐中，VBNET上的变体：

Dim maxLength = ValToInt(document.GetDataAnnotationPropertyAttributeValue(fieldName, GetType(MaxLengthAttribute)))
    
Public Function GetDataAnnotationPropertyAttributeValue(propertyName As String, attributeType As Type) As Object
            Dim properties = Me.GetType().GetProperties()
            Dim propertyInfo = properties.FirstOrDefault(Function(p) p.Name?.ToLower() = propertyName?.ToLower())
            If propertyInfo Is Nothing Then Return Nothing
    
            Dim attribute = propertyInfo.CustomAttributes.FirstOrDefault(Function(a) a.AttributeType.Equals(attributeType))
            Return attribute?.ConstructorArguments(0).Value
End Function
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