ITask Interface
Definition
Important
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This interface defines a "task" in the build system. A task is an atomic unit of build operation. All task classes must implement this interface to be recognized by the build engine.
public interface class ITaskpublic interface ITasktype ITask = interfacePublic Interface ITask- Derived
Examples
The following example shows the code from a complete task implementation.
using System;
using System.IO;
using System.Security;
using System.Collections;
using Microsoft.Build.Framework;
using Microsoft.Build.Utilities;
namespace Microsoft.Build.Tasks
{
/*
* Class: MakeDir
*
* An MSBuild task that creates one or more directories.
*
*/
public class MakeDir : Task
{
// The Required attribute indicates the following to MSBuild:
// - if the parameter is a scalar type, and it is not supplied, fail the build immediately
// - if the parameter is an array type, and it is not supplied, pass in an empty array
// In this case the parameter is an array type, so if a project fails to pass in a value for the
// Directories parameter, the task will get invoked, but this implementation will do nothing,
// because the array will be empty.
[Required]
// Directories to create.
public ITaskItem[] Directories
{
get
{
return directories;
}
set
{
directories = value;
}
}
// The Output attribute indicates to MSBuild that the value of this property can be gathered after the
// task has returned from Execute(), if the project has an <Output> tag under this task's element for
// this property.
[Output]
// A project may need the subset of the inputs that were actually created, so make that available here.
public ITaskItem[] DirectoriesCreated
{
get
{
return directoriesCreated;
}
}
private ITaskItem[] directories;
private ITaskItem[] directoriesCreated;
/// <summary>
/// Execute is part of the Microsoft.Build.Framework.ITask interface.
/// When it's called, any input parameters have already been set on the task's properties.
/// It returns true or false to indicate success or failure.
/// </summary>
public override bool Execute()
{
ArrayList items = new ArrayList();
foreach (ITaskItem directory in Directories)
{
// ItemSpec holds the filename or path of an Item
if (directory.ItemSpec.Length > 0)
{
try
{
// Only log a message if we actually need to create the folder
if (!Directory.Exists(directory.ItemSpec))
{
Log.LogMessage(MessageImportance.Normal, "Creating directory " + directory.ItemSpec);
Directory.CreateDirectory(directory.ItemSpec);
}
// Add to the list of created directories
items.Add(directory);
}
// If a directory fails to get created, log an error, but proceed with the remaining
// directories.
catch (Exception ex)
{
if (ex is IOException
|| ex is UnauthorizedAccessException
|| ex is PathTooLongException
|| ex is DirectoryNotFoundException
|| ex is SecurityException)
{
Log.LogError("Error trying to create directory " + directory.ItemSpec + ". " + ex.Message);
}
else
{
throw;
}
}
}
}
// Populate the "DirectoriesCreated" output items.
directoriesCreated = (ITaskItem[])items.ToArray(typeof(ITaskItem));
// Log.HasLoggedErrors is true if the task logged any errors -- even if they were logged
// from a task's constructor or property setter. As long as this task is written to always log an error
// when it fails, we can reliably return HasLoggedErrors.
return !Log.HasLoggedErrors;
}
}
}
Remarks
All task classes must implement this interface to be recognized by the build engine. Instead of implementing this interface directly, you can also derive your class from the helper class, Task, which provides default implementations of some ITask members.
Properties
| BuildEngine |
This property is set by the build engine to allow a task to call back into it. |
| HostObject |
The build engine sets this property if the host IDE has associated a host object with this particular task. |
Methods
| Execute() |
This method is called by the build engine to begin task execution. A task uses the return value to indicate whether it was successful. If a task throws an exception out of this method, the engine will automatically assume that the task has failed. |