Task Class

Definition

This helper base class provides default functionality for tasks. This class can only be instantiated in a derived form.

public ref class Task abstract : Microsoft::Build::Framework::ITask
public abstract class Task : Microsoft.Build.Framework.ITask
type Task = class
    interface ITask
Public MustInherit Class Task
Implements ITask
Inheritance
Task
Derived
Implements

Examples

The following example shows the code for a task that creates one or more directories.

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

This abstract class provides default implementations for the methods and properties of the ITask interface.

This class can only be instantiated in a derived form.

Constructors

Task()

Default (family) constructor.

Task(ResourceManager)

This (family) constructor allows derived task classes to register their resources.

Task(ResourceManager, String)

This (family) constructor allows derived task classes to register their resources, as well as provide a prefix for composing help keywords from string resource names. If the prefix is an empty string, then string resource names will be used verbatim as help keywords. For an example of how the prefix is used, see the TaskLoggingHelper.LogErrorWithCodeFromResources(string, object[]) method.

Properties

BuildEngine

The build engine automatically sets this property to allow tasks to call back into it.

BuildEngine2

The build engine automatically sets this property to allow tasks to call back into it. This is a convenience property so that task authors inheriting from this class do not have to cast the value from IBuildEngine to IBuildEngine2.

BuildEngine3

Retrieves the IBuildEngine3 version of the build engine interface provided by the host.

BuildEngine4

Retrieves the IBuildEngine4 version of the build engine interface provided by the host.

BuildEngine5

Retrieves the IBuildEngine5 version of the build engine interface provided by the host.

BuildEngine6

Retrieves the IBuildEngine6 version of the build engine interface provided by the host.

BuildEngine7

Retrieves the IBuildEngine7 version of the build engine interface provided by the host.

BuildEngine8

Retrieves the IBuildEngine8 version of the build engine interface provided by the host.

BuildEngine9

Retrieves the IBuildEngine9 version of the build engine interface provided by the host.

HelpKeywordPrefix

Gets or sets the prefix used to compose help keywords from string resource names. If a task does not have help keywords associated with its messages, it can ignore this property or set it to null. If the prefix is set to an empty string, then string resource names will be used verbatim as help keywords. For an example of how this prefix is used, see the TaskLoggingHelper.LogErrorWithCodeFromResources(string, object[]) method.

HostObject

The build engine sets this property if the host IDE has associated a host object with this particular task.

Log

Gets an instance of a TaskLoggingHelper class containing task logging methods. The taskLoggingHelper is a MarshallByRef object which needs to have MarkAsInactive called if the parent task is making the appdomain and marshaling this object into it. If the appdomain is not unloaded at the end of the task execution and the MarkAsInactive method is not called this will result in a leak of the task instances in the appdomain the task was created within.

TaskResources

Gets or sets the task's culture-specific resources. Derived classes should register their resources either during construction, or via this property, if they have localized strings.

Methods

Equals(Object)

Determines whether the specified object is equal to the current object.

(Inherited from Object)
Execute()

Must be implemented by derived class.

GetHashCode()

Serves as the default hash function.

(Inherited from Object)
GetType()

Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone()

Creates a shallow copy of the current Object.

(Inherited from Object)
ToString()

Returns a string that represents the current object.

(Inherited from Object)

Applies to