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前言

C#特性学习、主要是用在数据库连接时如何动态创建对应的表，正常开发应该使用如Entity Framework等ORM框架实现自动创建生成。

代码

1、声明特性

[AttributeUsage(AttributeTargets.Property)]
public class PrimaryKeyAttribute : Attribute { }[AttributeUsage(AttributeTargets.Property)]
public class ForeignKeyAttribute : Attribute
{public string ReferenceTable { get; }public string ReferenceColumn { get; }public ForeignKeyAttribute(string referenceTable, string referenceColumn){ReferenceTable = referenceTable;ReferenceColumn = referenceColumn;}
}[AttributeUsage(AttributeTargets.Property)]
public class RequiredAttribute : Attribute { }[AttributeUsage(AttributeTargets.Property)]
public class UniqueAttribute : Attribute { }

2、定义特性方法

//特性方法
public static class AttributeMethod
{//反射+泛型打印特性名public static void GetAttributies<T>(){Type objType = typeof(T);foreach (var property in objType.GetProperties()){Console.WriteLine($"Property: {property.Name}");if (property.GetCustomAttribute<PrimaryKeyAttribute>() != null){Console.WriteLine("  - Primary Key");}if (property.GetCustomAttribute<ForeignKeyAttribute>() != null){var foreignKey = property.GetCustomAttribute<ForeignKeyAttribute>();Console.WriteLine($"  - Foreign Key: References {foreignKey.ReferenceTable}.{foreignKey.ReferenceColumn}");}if (property.GetCustomAttribute<RequiredAttribute>() != null){Console.WriteLine("  - Required");}if (property.GetCustomAttribute<UniqueAttribute>() != null){Console.WriteLine("  - Unique");}}}
}

3、创建类并指定特性

public class User
{[PrimaryKey]public int Id { get; set; }[Required][Unique]public string Username { get; set; }[Required]public string Password { get; set; }[ForeignKey("Role", "Id")]public int RoleId { get; set; }
}public class Role
{[PrimaryKey]public int Id { get; set; }[Required]public string Name { get; set; }
}

调用方法获取并打印特性名

internal class Program
{static void Main(string[] args){Console.WriteLine("输出User特性:");AttributeMethod.GetAttributies<User>();Console.WriteLine();Console.WriteLine("输出Role特性:");AttributeMethod.GetAttributies<Role>();Console.ReadKey();}
}

结果