AssemblyBuilder.SetCustomAttribute Method (ConstructorInfo, Byte[])


Set a custom attribute on this assembly using a specified custom attribute blob.

Namespace:   System.Reflection.Emit
Assembly:  mscorlib (in mscorlib.dll)

public void SetCustomAttribute(
	ConstructorInfo con,
	byte[] binaryAttribute


Type: System.Reflection.ConstructorInfo

The constructor for the custom attribute.

Type: System.Byte[]

A byte blob representing the attributes.

Exception Condition

con or binaryAttribute is null.


The caller does not have the required permission.


con is not a RuntimeConstructorInfo object.

See the metadata specification in the ECMA Partition II documentation for details on how to format binaryAttribute. The documentation is available online; see ECMA C# and Common Language Infrastructure Standards on MSDN and Standard ECMA-335 - Common Language Infrastructure (CLI) on the Ecma International Web site.

RuntimeConstructorInfo is a special type generated by the system. It derives from the ConstructorInfo class, and any ConstructorInfo object you obtain through reflection is actually an instance of RuntimeConstructorInfo.


SetCustomAttribute cannot be used to set declarative security attributes. Use one of the overloads of DefineDynamicAssembly that takes required, optional, and refused permissions.


Starting with the .NET Framework 2.0 Service Pack 1, this member no longer requires ReflectionPermission with the ReflectionPermissionFlag.ReflectionEmit flag. (See Security Issues in Reflection Emit.) To use this functionality, your application should target the .NET Framework 3.5 or later.

The following code sample illustrates the use of SetCustomAttribute to attach a custom attribute to a dynamically generated assembly.

using System;
using System.Threading;
using System.Reflection;
using System.Reflection.Emit;

[AttributeUsage(AttributeTargets.All, AllowMultiple = false)]
public class MyAttribute : Attribute
   public bool s;

   public MyAttribute(bool s)
      this.s = s;

class MyApplication
   public static void Main()
      Type customAttribute = CreateCallee(Thread.GetDomain());
      object[] attributes = customAttribute.Assembly.GetCustomAttributes(true);
      Console.WriteLine("MyAttribute custom attribute contains : ");
      for(int index=0; index < attributes.Length; index++)
         if(attributes[index] is MyAttribute)
            Console.WriteLine("s : " + ((MyAttribute)attributes[index]).s);

   private static Type CreateCallee(AppDomain domain)
      AssemblyName myAssemblyName = new AssemblyName();
      myAssemblyName.Name = "EmittedAssembly";
      AssemblyBuilder myAssembly = domain.DefineDynamicAssembly(myAssemblyName,
      Type myType = typeof(MyAttribute);
      ConstructorInfo infoConstructor = myType.GetConstructor(new Type[]{typeof(bool)});
      myAssembly.SetCustomAttribute(infoConstructor, new byte[]{01,00,01});
      ModuleBuilder myModule = myAssembly.DefineDynamicModule("EmittedModule");
      // Define a public class named "HelloWorld" in the assembly.
      TypeBuilder helloWorldClass = myModule.DefineType("HelloWorld", TypeAttributes.Public);



when invoked late-bound through mechanisms such as Type.InvokeMember. Associated enumeration: ReflectionPermissionFlag.MemberAccess.

.NET Framework
Available since 1.1
Available since 2.0
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