CSharp扩展方法应用之获取特性

         例如在Asp.net MVC Web Application中的，我们想快速了解某个Action上是否有某个Attribute. 那我们可以使用这样的扩展方法:

    

/// <summary>
/// Gets the method.
/// </summary>
/// <typeparam name="T">Type</typeparam>
/// <param name="instance">The instance.</param>
/// <param name="methodSelector">The method selector.</param>
/// <returns>MethodInfo</returns>
public static MethodInfo GetMethod<T>(this T instance, Expression<Func<T, object>> methodSelector)
{
    // it is not work all method
    return ((MethodCallExpression)methodSelector.Body).Method;
}

/// <summary>
/// Gets the method.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="instance">The instance.</param>
/// <param name="methodSelector">The method selector.</param>
/// <returns>MethodInfo</returns>
public static MethodInfo GetMethod<T>(this T instance,
    Expression<Action<T>> methodSelector)
{
    return ((MethodCallExpression)methodSelector.Body).Method;
}

/// <summary>
/// Determines whether the specified member has attribute.
/// </summary>
/// <typeparam name="TAttribute">The type of the attribute.</typeparam>
/// <param name="member">The member.</param>
/// <returns>
///   <c>true</c> if the specified member has attribute; otherwise, <c>false</c>.
/// </returns>
public static bool HasAttribute<TAttribute>(
    this MemberInfo member)
    where TAttribute : Attribute
{
    return GetAttributes<TAttribute>(member).Length > 0;
}

/// <summary>
/// Gets the attributes.
/// </summary>
/// <typeparam name="TAttribute">The type of the attribute.</typeparam>
/// <param name="member">The member.</param>
/// <returns></returns>
public static TAttribute[] GetAttributes<TAttribute>(
    this MemberInfo member)
    where TAttribute : Attribute
{
    var attributes =
        member.GetCustomAttributes(typeof(TAttribute), true);

    return (TAttribute[])attributes;
}

如何使用，请看下面的代码，我们使用lambda表达式获取某个方法，然后获取其上面的Attribute:

[Fact]
public void GetHttpPostAttributeFromCreateAction()
{
    // Arrange
    var controller = GetEmployeeController(new MemeoryEmployeeBoService());
    
    //Act
    bool hasPostAttribute =controller.GetMethod(e => e.Create(new Employee()))
        .HasAttribute<HttpPostAttribute>();

    // Assert
    Assert.True(hasPostAttribute);
}

希望对您开发有帮助。

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作者：Petter Liu
出处：http://www.cnblogs.com/wintersun/
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该文章也同时发布在我的独立博客中-Petter Liu Blog。