Attribute on attribute itself

10 Feb 2022 1 mins C#

Today I learned that you could use attribute, in C#, on itself. 🤯 Not sure why would I do that, but it’s cool.

This simple C# code…

[My]
public class MyAttribute : Attribute
{ }

…compiles into this IL just fine.

.class public auto ansi beforefieldinit MyAttribute
    extends [System.Private.CoreLib]System.Attribute
{
    .custom instance void MyAttribute::.ctor() = (
        01 00 00 00
    )
    // Methods
    .method public hidebysig specialname rtspecialname 
        instance void .ctor () cil managed 
    {
        // Method begins at RVA 0x2050
        // Code size 7 (0x7)
        .maxstack 8

        IL_0000: ldarg.0
        IL_0001: call instance void [System.Private.CoreLib]System.Attribute::.ctor()
        IL_0006: ret
    } // end of method MyAttribute::.ctor

} // end of class MyAttribute

I, obviously, never needed that before. And I don’t know what I would use it realistically for. But I’ll put this into “cool facts for beer talk” drawer.

Jiří Činčura is .NET, C# and Firebird expert. He focuses on data and business layers, language constructs, parallelism, databases and performance. For almost two decades he contributes to open-source, i.e. FirebirdClient. He works as a senior software engineer for Microsoft. Frequent speaker and blogger at www.tabsoverspaces.com.