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AssemblyBuilder.DefineDynamicModule Method (String, String, Boolean)

Defines a persistable dynamic module, specifying the module name, the name of the file to which the module will be saved, and whether symbol information should be emitted using the default symbol writer.

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

public ModuleBuilder DefineDynamicModule(
	string name,
	string fileName,
	bool emitSymbolInfo


Type: System.String

The name of the dynamic module. Must be less than 260 characters in length.

Type: System.String

The name of the file to which the dynamic module should be saved.

Type: System.Boolean

If true, symbolic information is written using the default symbol writer.

Return Value

Type: System.Reflection.Emit.ModuleBuilder
A ModuleBuilder object representing the defined dynamic module.


name or fileName is null.


The length of name or fileName is zero.


The length of name is greater than or equal to 260.


fileName contains a path specification (a directory component, for example).


There is a conflict with the name of another file that belongs to this assembly.


This assembly has been previously saved.


This assembly was called on a dynamic assembly with the Run attribute.


The assembly for default symbol writer cannot be loaded.


The type that implements the default symbol writer interface cannot be found.


The caller does not have the required permission.

To define a persistable dynamic module, this assembly needs to be created with the Save or the RunAndSave attribute.

If you want the module to contain the assembly manifest, name should be the same as the name of the assembly (that is, the AssemblyName.Name property of the AssemblyName used to create the dynamic assembly) and fileName should be the same as the filename you specify when you save the assembly.

In an assembly with only one module, that module should contain the assembly manifest.


To suppress optimizations when debugging dynamic modules, apply the DebuggableAttribute attribute to the dynamic assembly before calling DefineDynamicModule. Create an instance of DebuggableAttribute with the DisableOptimizations flag and apply it using the SetCustomAttribute method. The attribute must be applied to the dynamic assembly. It has no effect if applied to the module.


Starting with the .NET Framework version 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 version 3.5. For more information, see .NET Framework 3.5 Architecture.

[Visual Basic, C#]

The code example below demonstrates how to create a persistent dynamic module with symbol emission using DefineDynamicModule.

	   AppDomain myAppDomain = Thread.GetDomain(); 
	   AssemblyName myAsmName = new AssemblyName();
	   myAsmName.Name = "MyAssembly";
	   AssemblyBuilder myAsmBuilder = myAppDomain.DefineDynamicAssembly(
	   // Create a dynamic module that can be saved as the specified DLL name. By 
	   // specifying the third parameter as true, we can allow the emission of symbol info.
	   ModuleBuilder myModuleBuilder = myAsmBuilder.DefineDynamicModule("MyModule4",

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0