以下实例，定义了一个自定义特性Author、将其应用于多个实体，并通过反射对其进行检索。本实例代码使用了顶级语句，须在.NET 5(C# 9.0)以上环境中使用。

Console.WriteLine("Hello, Hovertree!This is a sample of Attribute.");//顶级语句，须在.NET 5（C# 9.0）以上环境中使用
TestAuthorAttribute.Test();
Console.ReadLine();

// Multiuse attribute.  
[System.AttributeUsage(System.AttributeTargets.Class |
                       System.AttributeTargets.Struct,
                       AllowMultiple = true)  // Multiuse attribute.  
]
public class Author : System.Attribute
{
    string name;
    public double version;

    public Author(string name)
    {
        this.name = name;

        // Default value.  
        version = 1.0;
    }

    public string GetName()
    {
        return name;
    }
}

// Class with the Author attribute.  
[Author("W. Hovertree")]
public class FirstClass
{
    // ...  
}

// Class without the Author attribute.  
public class SecondClass
{
    // ...  
}

// Class with multiple Author attributes.  
[Author("H. Ackerman"), Author("R. Koch", version = 2.0)]
public class ThirdClass
{
    // ...  
}

class TestAuthorAttribute
{
    public static void Test()
    {
        PrintAuthorInfo(typeof(FirstClass));
        PrintAuthorInfo(typeof(SecondClass));
        PrintAuthorInfo(typeof(ThirdClass));
    }

    private static void PrintAuthorInfo(System.Type t)
    {
        System.Console.WriteLine("Author information for {0}", t);

        // Using reflection.  
        System.Attribute[] attrs = System.Attribute.GetCustomAttributes(t);  // Reflection.  

        // Displaying output.  
        foreach (System.Attribute attr in attrs)
        {
            if (attr is Author)
            {
                Author a = (Author)attr;
                System.Console.WriteLine("   {0}, version {1:f}", a.GetName(), a.version);
            }
        }
    }
}
/* 
调用TestAuthorAttribute类的Test()方法的输出如下：
 
Hello, Hovertree!This is a sample of Attribute.
Author information for FirstClass
   W. Hovertree, version 1.00
Author information for SecondClass
Author information for ThirdClass
   H. Ackerman, version 1.00
   R. Koch, version 2.00  
*/

运行效果如下图：