Compiler Error CS0579

 

Updated: July 20, 2015

For the latest documentation on Visual Studio 2017 RC, see Visual Studio 2017 RC Documentation.

Duplicate 'attribute' attribute

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

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()  
    {  
    }  
}  

Show: