如何从code检索数据注释？ （编程） [英] How to retrieve Data Annotations from code? (programmatically)

问题描述

我用 System.ComponentModel.DataAnnotations 来为我的实体框架4.1的项目提供验证。

I'm using System.ComponentModel.DataAnnotations to provide validation for my Entity Framework 4.1 project.

例如：

public class Player
{
    [Required]
    [MaxLength(30)]
    [Display(Name = "Player Name")]
    public string PlayerName { get; set; }

    [MaxLength(100)]
    [Display(Name = "Player Description")]
    public string PlayerDescription{ get; set; }
}

我需要检索 Display.Name 注释值的消息显示它如的选择的玩家名是弗兰克。的

I need to retrieve the Display.Name annotation value to show it in a message such as The chosen "Player Name" is Frank.

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为什么我会需要检索注释又如：

Another example of why I could need to retrieve annotations:

var playerNameTextBox = new TextBox();
playerNameTextBox.MaxLength = GetAnnotation(myPlayer.PlayerName, MaxLength);

我怎么能这样做？

How can I do that?

推荐答案

扩展方法：

public static T GetAttributeFrom<T>(this object instance, string propertyName) where T : Attribute
{
    var attrType = typeof(T);
    var property = instance.GetType().GetProperty(propertyName);
    return (T)property .GetCustomAttributes(attrType, false).First();
}

code：

var name = player.GetAttributeFrom<DisplayAttribute>("PlayerDescription").Name;
var maxLength = player.GetAttributeFrom<MaxLengthAttribute>("PlayerName").Length;

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