Compiler Error CS0579

Duplicate 'attribute' attribute

It is not possible to specify the same attribute more than once unless the attribute specifies AllowMultiple=true in its AttributeUsage.

Example

The following example generates CS0579.

// CS0579.cs  
using System;  
public class MyAttribute : Attribute  
{  
}  

[AttributeUsage(AttributeTargets.All,AllowMultiple=true)]  
public class MyAttribute2 : Attribute  
{  
}  

public class z  
{  
    [MyAttribute, MyAttribute]     // CS0579  
    public void zz()  
    {  
    }  

    [MyAttribute2, MyAttribute2]   // OK  
    public void zzz()  
    {  
    }  

    public static void Main()  
    {  
    }  
}