AppDomainSetup.DynamicBase Property


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Gets or sets the base directory where the directory for dynamically generated files is located.

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

public string DynamicBase { get; set; }

Property Value

Type: System.String

The directory where the AppDomain.DynamicDirectory is located.


The return value of this property is different from the value assigned. See the Remarks section.

Exception Condition

This property cannot be set because the application name on the application domain is null.

Use this property to set the base directory where the dynamic directory for the new application domain will be located. When code in the new application domain loads an assembly, assembly resolution looks first in the normal probing paths. If it does not find the assembly, it looks in the dynamic directory, which is returned by the AppDomain.DynamicDirectory property. Dynamic assemblies that will be loaded and executed by the new application domain can be placed there.

When you assign a path to the DynamicBase property, an additional subdirectory is added; the name of this subdirectory is the hash code of the value assigned to the ApplicationName property. Thus, the base directory subsequently returned by this property is always different from the value assigned.


Assigning a value to this property does not create any directories. The directories must be created or verified by the code that uses them.

The dynamic directory is a subdirectory of DynamicBase. Its simple name is the value returned by the ApplicationName property, so its format is original path\hash code\application name.

The following example demonstrates how to use the DynamicBase property to set the path an application domain probes when loading dynamic assemblies.

The example creates an AppDomainSetup object and sets its ApplicationName property to "Example" and its DynamicBase property to "C:\DynamicAssemblyDir". The example then displays the DynamicBase property, to show that the hash code of the application name has been appended as a subdirectory of the path that was originally assigned.


The base directory in this example is intended to be outside the probing path for the example application. Be sure to compile the example in a different location. Delete the base directory and all its subdirectories each time you run the example.

The example creates a new application domain using the AppDomainSetup object. The example then creates the dynamic directory if it does not already exist. Although the example uses the application domain's AppDomain.DynamicDirectory property to get the name of the dynamic directory, it could just as easily create the directory beforehand by concatenating the original path, the hash code of the application name, and the application name.

The example has a GenerateDynamicAssembly method that emits an assembly named DynamicHelloWorld.dll and stores it in the new application domain's dynamic directory. The dynamic assembly contains one type, HelloWorld, that has a static method (Shared method in Visual Basic) named HelloFromAD. Calling this method displays the name of the application domain.

The Example class derives from MarshalByRefObject, so the example can create an instance of the class in the new application domain and call its Test method. The Test method loads the dynamic assembly by its display name and calls the static HelloFromAD method.

You can show that the dynamic directory is searched after the normal probing paths by writing code for an assembly named DynamicHelloWorld.dll and compiling it in the same directory as this example. The assembly must have a class named HelloWorld with a static method named HelloFromAD. This method does not have to have the same functionality as the one in the example; it can simply display a string to the console. The assembly must also have an AssemblyVersionAttribute attribute that sets its version to When you run the example, the assembly you compiled in the current directory is found before the dynamic directory is searched.

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

public class Example : MarshalByRefObject
   static void Main()
      // Prepare to create a new application domain.
      AppDomainSetup setup = new AppDomainSetup();

      // Set the application name before setting the dynamic base.
      setup.ApplicationName = "Example";

      // Set the location of the base directory where assembly resolution 
      // probes for dynamic assemblies. Note that the hash code of the 
      // application name is concatenated to the base directory name you 
      // supply. 
      setup.DynamicBase = "C:\\DynamicAssemblyDir";
      Console.WriteLine("DynamicBase is set to '{0}'.", setup.DynamicBase);

      AppDomain ad = AppDomain.CreateDomain("MyDomain", null, setup);

      // The dynamic directory name is the dynamic base concatenated with
      // the application name: <DynamicBase>\<hash code>\<ApplicationName>
      string dynamicDir = ad.DynamicDirectory;
      Console.WriteLine("Dynamic directory is '{0}'.", dynamicDir);

      // The AssemblyBuilder won't create this directory automatically.
      if (!System.IO.Directory.Exists(dynamicDir))
         Console.WriteLine("Creating the dynamic directory.");

      // Generate a dynamic assembly and store it in the dynamic 
      // directory.

      // Create an instance of the Example class in the application domain,
      // and call its Test method to load the dynamic assembly and use it.
      Example ex = (Example) ad.CreateInstanceAndUnwrap(
         typeof(Example).Assembly.FullName, "Example");

   public void Test()
      Assembly dynAssem = Assembly.Load(
         "DynamicHelloWorld, Version=, Culture=neutral, PublicKeyToken=null");

      Type myType = dynAssem.GetType("HelloWorld");
      myType.InvokeMember("HelloFromAD", BindingFlags.Public | 
         BindingFlags.Static | BindingFlags.InvokeMethod, 
         Type.DefaultBinder, null, null);

   private static void GenerateDynamicAssembly(string location)
      // Define the dynamic assembly and the module. There is only one
      // module in this assembly. Note that the call to DefineDynamicAssembly 
      // specifies the location where the assembly will be saved. The 
      // assembly version is
      AssemblyName asmName = new AssemblyName("DynamicHelloWorld");
      asmName.Version = new Version("");

      AssemblyBuilder ab = 
            asmName, AssemblyBuilderAccess.Save, location);

      String moduleName = asmName.Name + ".exe";
      ModuleBuilder mb = ab.DefineDynamicModule(asmName.Name, moduleName);

      // Define the "HelloWorld" type, with one static method.
      TypeBuilder tb = mb.DefineType("HelloWorld", TypeAttributes.Public);
      MethodBuilder hello = tb.DefineMethod("HelloFromAD", 
         MethodAttributes.Public | MethodAttributes.Static, null, null);

      // The method displays a message that contains the name of the application
      // domain where the method is executed.
      ILGenerator il = hello.GetILGenerator();
      il.Emit(OpCodes.Ldstr, "Hello from '{0}'!");
      il.Emit(OpCodes.Call, typeof(AppDomain).GetProperty("CurrentDomain").GetGetMethod());
      il.Emit(OpCodes.Call, typeof(AppDomain).GetProperty("FriendlyName").GetGetMethod());
      il.Emit(OpCodes.Call, typeof(Console).GetMethod("WriteLine", 
                             new Type[] { typeof(String), typeof(String) }));

      // Complete the HelloWorld type and save the assembly. The assembly
      // is placed in the location specified by DefineDynamicAssembly.
      Type myType = tb.CreateType();

/* This example produces output similar to the following:

DynamicBase is set to 'C:\DynamicAssemblyDir\5e4a7545'.
Dynamic directory is 'C:\DynamicAssemblyDir\5e4a7545\Example'.
Creating the dynamic directory.
Hello from 'MyDomain'!


for access to the path information. Associated enumeration: FileIOPermissionAccess.PathDiscovery

.NET Framework
Available since 1.1
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