RequiredAttribute Class
Defines the metadata attribute that task authors use to identify required task properties. Task properties with this attribute must have a set value when the task is run.
MSBuild is now included in Visual Studio instead of the .NET Framework. You can use MSBuild 12.0 side-by-side with versions previously deployed with the .NET Framework.For more information, see What's New in MSBuild 12.0.
Inheritance Hierarchy
System.Object
System.Attribute
Microsoft.Build.Framework.RequiredAttribute
Namespace: Microsoft.Build.Framework
Assembly: Microsoft.Build.Framework (in Microsoft.Build.Framework.dll)
Syntax
'Declaration
<AttributeUsageAttribute(AttributeTargets.Property, AllowMultiple := False, _
Inherited := False)> _
Public NotInheritable Class RequiredAttribute _
Inherits Attribute
[AttributeUsageAttribute(AttributeTargets.Property, AllowMultiple = false,
Inherited = false)]
public sealed class RequiredAttribute : Attribute
[AttributeUsageAttribute(AttributeTargets::Property, AllowMultiple = false,
Inherited = false)]
public ref class RequiredAttribute sealed : public Attribute
[<Sealed>]
[<AttributeUsageAttribute(AttributeTargets.Property, AllowMultiple = false,
Inherited = false)>]
type RequiredAttribute =
class
inherit Attribute
end
public final class RequiredAttribute extends Attribute
The RequiredAttribute type exposes the following members.
Constructors
| Name | Description | |
|---|---|---|
.gif "Public method") |
RequiredAttribute | Initializes a new instance of the RequiredAttribute class.MSBuild is now included in Visual Studio instead of the .NET Framework. You can use MSBuild 12.0 side-by-side with versions previously deployed with the .NET Framework.For more information, see What's New in MSBuild 12.0. |
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Properties
| Name | Description | |
|---|---|---|
.gif "Public property") |
TypeId | (Inherited from Attribute.) |
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Methods
| Name | Description | |
|---|---|---|
|
Equals | (Inherited from Attribute.) |
|
GetHashCode | (Inherited from Attribute.) |
|
GetType | (Inherited from Object.) |
|
IsDefaultAttribute | (Inherited from Attribute.) |
|
Match | (Inherited from Attribute.) |
|
ToString | (Inherited from Object.) |
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Explicit Interface Implementations
| Name | Description | |
|---|---|---|
.gif "Explicit interface implemetation") .gif "Private method") |
System#Runtime#InteropServices#_Attribute#GetIDsOfNames | (Inherited from Attribute.) |
|
System#Runtime#InteropServices#_Attribute#GetTypeInfo | (Inherited from Attribute.) |
|
System#Runtime#InteropServices#_Attribute#GetTypeInfoCount | (Inherited from Attribute.) |
|
System#Runtime#InteropServices#_Attribute#Invoke | (Inherited from Attribute.) |
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Remarks
If a property marked with this attribute is not assigned a value when the task is invoked, the build will fail.
For more information about using attributes, see Extending Metadata Using Attributes.
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;
}
}
}
To run this task use a project file like this:
<Project xmlns="https://schemas.microsoft.com/developer/msbuild/2003">
<Target Name="MyTarget">
<MkDir Directories="NewDir" />
</Target>
</Project>
Thread Safety
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.