Customize Your Builds in Visual Studio Using the Standalone MSBuild Tool : Page 3

First, what exactly is a 'user-defined Task'? Simply put, it's a managed class implementing the interface Microsoft.Build.Framework.ITask defined in the assembly MSBuildFramework.dll. Let's have a look at the definition of the interface:

public interface ITask
{
   public bool Execute();
   public IBuildEngine BuildEngine { get; set; }
   public object HostObject { get; set; }
}

Figure 1. The Class Model: This image shows the class model that is located behind a Task.

The most important method is Execute. Execute is called when the Task is started through MSBuild. Furthermore you can find in the namespace Microsoft.Build.Utilities (assembly MSBuildUtilities) the class Task that is already implementing the interface ITask. The only thing you must do when deriving from this class is override the method Execute and implement your own build process logic to execute. Figure 1 shows the class model that is located behind a Task.

Your own Tasks must be registered within MSBuild when you want to use them. For the registration you can use the XML element <UsingTask> within the project file, as shown here:

<Project MSBuildVersion="2.0" DefaultTargets="MainTarget" 
   xmlns="http://schemas.microsoft.com/developer/
   msbuild/2003">
   <UsingTask TaskName="MyNamespace.MyTaskClass" 
      AssemblyName="MyAssembly" />
</Project>

using System;
using System.Windows.Forms;
using Microsoft.Build.Framework;
using Microsoft.Build.Utilities;

namespace MyTasks
{
   public class HelloWorld : Task
   {
      public override bool Execute()
      {
         MessageBox.Show("Hello World from MSBuild!");
         return true;
      }
   }
}

<Project MSBuildVersion="2.0" DefaultTargets="MainTarget" 
   xmlns="http://schemas.microsoft.com/developer/
   msbuild/2003">
   <UsingTask TaskName="MyTasks.HelloWorld" 
      AssemblyName="MyAssembly" />

   <Target Name="MainTarget">
      <HelloWorld />
   </Target>
</Project>

The following example declares the property Files that accepts a list of files for which the last write time should be changed to the current time. Furthermore this property is marked with the attribute MSBuild is completely extensible and scalable for large-scale enterprise applications. MSBuild was used for several years internally at Microsoft for building its own software products. Even better, there are rumors that Microsoft may decide to migrate the whole build process for Longhorn to MSBuild. While that doesn't change what MSBuild can do for you it does provide some welcome 'eating their own dog food'-level comfort. If Longhorn can be built with MSBuild then this tool is a first-class citizen for our own enterprise applications.