开发中灵活使用属性类-阿里云开发者社区

什么是属性类？

从抽象类System.Attribute派生出来的类（无论是直接的还是间接的）都称为属性类（MSDN中的定义）。

属性类的名称一般都带有Attribute后缀，但使用的时候可以包含也可以忽略，如果你自己起的名字没有这个后缀，则需要全称来区分了。如果不怕输入麻烦，建议还是不管是否有后缀，都输入全称为好，这样可以减少歧义。

在.NET框架中差不多定义了200个Attribute相关类，可见Attribute的应用十分广泛，它的全图在MSDN中如下：

System.Object

System.Attribute

System.AttributeUsageAttribute

System.CLSCompliantAttribute

System.ComponentModel.AmbientValueAttribute

System.ComponentModel.BindableAttribute

System.ComponentModel.BrowsableAttribute

System.ComponentModel.CategoryAttribute

System.ComponentModel.DefaultEventAttribute

System.ComponentModel.DefaultPropertyAttribute

System.ComponentModel.DefaultValueAttribute

System.ComponentModel.DescriptionAttribute

System.ComponentModel.Design.Serialization.DesignerSerializerAttribute

System.ComponentModel.Design.Serialization.RootDesignerSerializerAttribute

System.ComponentModel.DesignerAttribute

System.ComponentModel.DesignerCategoryAttribute

System.ComponentModel.DesignerSerializationVisibilityAttribute

System.ComponentModel.DesignOnlyAttribute

System.ComponentModel.DesignTimeVisibleAttribute

System.ComponentModel.EditorAttribute

System.ComponentModel.EditorBrowsableAttribute

System.ComponentModel.ImmutableObjectAttribute

System.ComponentModel.InheritanceAttribute

System.ComponentModel.InstallerTypeAttribute

System.ComponentModel.LicenseProviderAttribute

System.ComponentModel.ListBindableAttribute

System.ComponentModel.LocalizableAttribute

System.ComponentModel.MergablePropertyAttribute

System.ComponentModel.NotifyParentPropertyAttribute

System.ComponentModel.ParenthesizePropertyNameAttribute

System.ComponentModel.PropertyTabAttribute

System.ComponentModel.ProvidePropertyAttribute

System.ComponentModel.ReadOnlyAttribute

System.ComponentModel.RecommendedAsConfigurableAttribute

System.ComponentModel.RefreshPropertiesAttribute

System.ComponentModel.RunInstallerAttribute

System.ComponentModel.ToolboxItemAttribute

System.ComponentModel.ToolboxItemFilterAttribute

System.ComponentModel.TypeConverterAttribute

System.ContextStaticAttribute

System.Diagnostics.ConditionalAttribute

System.Diagnostics.DebuggableAttribute

System.Diagnostics.DebuggerHiddenAttribute

System.Diagnostics.DebuggerStepThroughAttribute

System.Drawing.ToolboxBitmapAttribute

System.EnterpriseServices.ApplicationAccessControlAttribute

System.EnterpriseServices.ApplicationActivationAttribute

System.EnterpriseServices.ApplicationIDAttribute

System.EnterpriseServices.ApplicationNameAttribute

System.EnterpriseServices.ApplicationQueuingAttribute

System.EnterpriseServices.AutoCompleteAttribute

System.EnterpriseServices.CompensatingResourceManager.ApplicationCrmEnabledAttribute

System.EnterpriseServices.ComponentAccessControlAttribute

System.EnterpriseServices.COMTIIntrinsicsAttribute

System.EnterpriseServices.ConstructionEnabledAttribute

System.EnterpriseServices.DescriptionAttribute

System.EnterpriseServices.EventClassAttribute

System.EnterpriseServices.EventTrackingEnabledAttribute

System.EnterpriseServices.ExceptionClassAttribute

System.EnterpriseServices.IISIntrinsicsAttribute

System.EnterpriseServices.InterfaceQueuingAttribute

System.EnterpriseServices.JustInTimeActivationAttribute

System.EnterpriseServices.LoadBalancingSupportedAttribute

System.EnterpriseServices.MustRunInClientContextAttribute

System.EnterpriseServices.ObjectPoolingAttribute

System.EnterpriseServices.PrivateComponentAttribute

System.EnterpriseServices.SecureMethodAttribute

System.EnterpriseServices.SecurityRoleAttribute

System.EnterpriseServices.SynchronizationAttribute

System.EnterpriseServices.TransactionAttribute

System.FlagsAttribute

System.LoaderOptimizationAttribute

System.Management.Instrumentation.IgnoreMemberAttribute

System.Management.Instrumentation.InstrumentationClassAttribute

System.Management.Instrumentation.InstrumentedAttribute

System.Management.Instrumentation.ManagedNameAttribute

System.MTAThreadAttribute

System.NonSerializedAttribute

System.ObsoleteAttribute

System.ParamArrayAttribute

System.Reflection.AssemblyAlgorithmIdAttribute

System.Reflection.AssemblyCompanyAttribute

System.Reflection.AssemblyConfigurationAttribute

System.Reflection.AssemblyCopyrightAttribute

System.Reflection.AssemblyCultureAttribute

System.Reflection.AssemblyDefaultAliasAttribute

System.Reflection.AssemblyDelaySignAttribute

System.Reflection.AssemblyDescriptionAttribute

System.Reflection.AssemblyFileVersionAttribute

System.Reflection.AssemblyFlagsAttribute

System.Reflection.AssemblyInformationalVersionAttribute

System.Reflection.AssemblyKeyFileAttribute

System.Reflection.AssemblyKeyNameAttribute

System.Reflection.AssemblyProductAttribute

System.Reflection.AssemblyTitleAttribute

System.Reflection.AssemblyTrademarkAttribute

System.Reflection.AssemblyVersionAttribute

System.Reflection.DefaultMemberAttribute

System.Resources.NeutralResourcesLanguageAttribute

System.Resources.SatelliteContractVersionAttribute

System.Runtime.CompilerServices.AccessedThroughPropertyAttribute

System.Runtime.CompilerServices.CompilationRelaxationsAttribute

System.Runtime.CompilerServices.CompilerGlobalScopeAttribute

System.Runtime.CompilerServices.CustomConstantAttribute

System.Runtime.CompilerServices.DecimalConstantAttribute

System.Runtime.CompilerServices.DiscardableAttribute

System.Runtime.CompilerServices.IndexerNameAttribute

System.Runtime.CompilerServices.MethodImplAttribute

System.Runtime.CompilerServices.RequiredAttributeAttribute

System.Runtime.InteropServices.AutomationProxyAttribute

System.Runtime.InteropServices.BestFitMappingAttribute

System.Runtime.InteropServices.ClassInterfaceAttribute

System.Runtime.InteropServices.CoClassAttribute

System.Runtime.InteropServices.ComAliasNameAttribute

System.Runtime.InteropServices.ComCompatibleVersionAttribute

System.Runtime.InteropServices.ComConversionLossAttribute

System.Runtime.InteropServices.ComEventInterfaceAttribute

System.Runtime.InteropServices.ComImportAttribute

System.Runtime.InteropServices.ComRegisterFunctionAttribute

System.Runtime.InteropServices.ComSourceInterfacesAttribute

System.Runtime.InteropServices.ComUnregisterFunctionAttribute

System.Runtime.InteropServices.ComVisibleAttribute

System.Runtime.InteropServices.DispIdAttribute

System.Runtime.InteropServices.DllImportAttribute

System.Runtime.InteropServices.FieldOffsetAttribute

System.Runtime.InteropServices.GuidAttribute

System.Runtime.InteropServices.IDispatchImplAttribute

System.Runtime.InteropServices.ImportedFromTypeLibAttribute

System.Runtime.InteropServices.InAttribute

System.Runtime.InteropServices.InterfaceTypeAttribute

System.Runtime.InteropServices.LCIDConversionAttribute

System.Runtime.InteropServices.MarshalAsAttribute

System.Runtime.InteropServices.OptionalAttribute

System.Runtime.InteropServices.OutAttribute

System.Runtime.InteropServices.PreserveSigAttribute

System.Runtime.InteropServices.PrimaryInteropAssemblyAttribute

System.Runtime.InteropServices.ProgIdAttribute

System.Runtime.InteropServices.StructLayoutAttribute

System.Runtime.InteropServices.TypeLibFuncAttribute

System.Runtime.InteropServices.TypeLibTypeAttribute

System.Runtime.InteropServices.TypeLibVarAttribute

System.Runtime.InteropServices.TypeLibVersionAttribute

System.Runtime.Remoting.Messaging.OneWayAttribute

System.Runtime.Remoting.Metadata.SoapAttribute

System.Runtime.Remoting.Proxies.ProxyAttribute

System.Security.AllowPartiallyTrustedCallersAttribute

System.Security.Permissions.SecurityAttribute

System.Security.SuppressUnmanagedCodeSecurityAttribute

System.Security.UnverifiableCodeAttribute

System.SerializableAttribute

System.STAThreadAttribute

System.ThreadStaticAttribute

System.Web.Services.Configuration.XmlFormatExtensionAttribute

System.Web.Services.Configuration.XmlFormatExtensionPointAttribute

System.Web.Services.Configuration.XmlFormatExtensionPrefixAttribute

System.Web.Services.Protocols.HttpMethodAttribute

System.Web.Services.Protocols.MatchAttribute

System.Web.Services.Protocols.SoapDocumentMethodAttribute

System.Web.Services.Protocols.SoapDocumentServiceAttribute

System.Web.Services.Protocols.SoapExtensionAttribute

System.Web.Services.Protocols.SoapHeaderAttribute

System.Web.Services.Protocols.SoapRpcMethodAttribute

System.Web.Services.Protocols.SoapRpcServiceAttribute

System.Web.Services.WebMethodAttribute

System.Web.Services.WebServiceAttribute

System.Web.Services.WebServiceBindingAttribute

System.Web.UI.ConstructorNeedsTagAttribute

System.Web.UI.ControlBuilderAttribute

System.Web.UI.DataBindingHandlerAttribute

System.Web.UI.ParseChildrenAttribute

System.Web.UI.PartialCachingAttribute

System.Web.UI.PersistChildrenAttribute

System.Web.UI.PersistenceModeAttribute

System.Web.UI.TagPrefixAttribute

System.Web.UI.TemplateContainerAttribute

System.Web.UI.ToolboxDataAttribute

System.Web.UI.ValidationPropertyAttribute

System.Xml.Serialization.SoapAttributeAttribute

System.Xml.Serialization.SoapElementAttribute

System.Xml.Serialization.SoapEnumAttribute

System.Xml.Serialization.SoapIgnoreAttribute

System.Xml.Serialization.SoapIncludeAttribute

System.Xml.Serialization.SoapTypeAttribute

System.Xml.Serialization.XmlAnyAttributeAttribute

System.Xml.Serialization.XmlAnyElementAttribute

System.Xml.Serialization.XmlArrayAttribute

System.Xml.Serialization.XmlArrayItemAttribute

System.Xml.Serialization.XmlAttributeAttribute

System.Xml.Serialization.XmlChoiceIdentifierAttribute

System.Xml.Serialization.XmlElementAttribute

System.Xml.Serialization.XmlEnumAttribute

System.Xml.Serialization.XmlIgnoreAttribute

System.Xml.Serialization.XmlIncludeAttribute

System.Xml.Serialization.XmlNamespaceDeclarationsAttribute

System.Xml.Serialization.XmlRootAttribute

System.Xml.Serialization.XmlTextAttribute

System.Xml.Serialization.XmlTypeAttribute

System.STAThreadAttribute
大家在一般使用中会留意到这个属性吗？用VS.NET新建一个项目，往往在main前面会如下面所示：

/// <summary>

/// 应用程序的主入口点。

/// </summary>

[STAThread]

static void Main()

{

Application.Run(new frmMain());

}

其实这个就是属性类STAThreadAttribute了，它的作用表示应用程序的COM线程模型是单线程单元（STA）。

属性类的实用性：

1.利用XML相关的属性类，将相关业务类XML序列化，可以达到保存状态和远程传输交换类信息等作用。
共14个和XML相关的属性类：
System.Xml.Serialization.XmlAnyAttributeAttribute
System.Xml.Serialization.XmlAnyElementAttribute
System.Xml.Serialization.XmlArrayAttribute
System.Xml.Serialization.XmlArrayItemAttribute
System.Xml.Serialization.XmlAttributeAttribute
System.Xml.Serialization.XmlChoiceIdentifierAttribute
System.Xml.Serialization.XmlElementAttribute
System.Xml.Serialization.XmlEnumAttribute
System.Xml.Serialization.XmlIgnoreAttribute
System.Xml.Serialization.XmlIncludeAttribute
System.Xml.Serialization.XmlNamespaceDeclarationsAttribute
System.Xml.Serialization.XmlRootAttribute
System.Xml.Serialization.XmlTextAttribute
System.Xml.Serialization.XmlTypeAttribute

最近做一个项目，需要将一些界面输入的有一定结构规律的信息保存起来，然后下次需要时候可以调入到对应的界面位置上使用。（其实这个是很多应用都会碰到的）。结构和UI的对应关系可能会经常变动的，而且结构中需要填写的内容不是所有都必须的，直接用关系型数据库来保存似乎不是太好的方案。首先想到就是用XML文件来保存这些信息了，而界面之间的信息显示是有关联的，可以说需要一个缓冲来记录这些信息，想到的就是定义一个类来记录和操作这些信息。这自然遇到一个问题，如何保持类和XML数据的同步呢？

生成的XML文件需要给其它业务来做处理，格式上有一定的规范，对于类来说，信息都保存在字段或者属性那里的，并没有区别，但XML中可能有些信息是Attribute,有些又是Element的。如何灵活地处理这些关系呢？用与XML相关的属性来定义这些字段和类就可以了。

(1) 类信息序列化到XML文件中的代码

public void SerializeObject( string filename)

{

XmlSerializer s = new XmlSerializer(typeof(Tables));

TextWriter writer = new StreamWriter(filename);

Tables group = new Tables();

group.GroupID = 10.089f;

group.IsActive = false;

group.HexBytes = new byte[1]{Convert.ToByte(100)};

Employee x = new Employee();

Employee y = new Employee();

x.Name = "Jack";

y.Name = "Jill";

x.des2 = "Yyyy

x.colType = new ColumnType[2];

x.colType[0] = new ColumnType();

x.colType[1] = new ColumnType();

x.colType[0].linkField = "Haaa

x.colType[1].linkType = "Zzzz

y.Age[0] = 20;

y.Age[1] = 40;

y.Desc = "OK";

group.Employees = new Employee[2]{x,y};

Manager mgr = new Manager();

mgr.Name = "Sara";

mgr.Level = 4;

mgr.Desc = "Yes";

mgr.aHead = true;

group.Manager = mgr;

group.ExtraInfo = new ArrayList();

group.ExtraInfo.Add(42);

group.ExtraInfo.Add("Answer");

s.Serialize(writer, group);

writer.Close();

}

(2) XML文件信息变成类的信息的代码

public void DeserializeObject( string filename)

{

FileStream fs = new FileStream(filename, FileMode.Open);

XmlSerializer x = new XmlSerializer(typeof(Tables));

Tables g = (Tables) x.Deserialize(fs);

int i=0;

foreach(Employee e in g.Employees)

{

i = i + 1;

Console.WriteLine("No {0} Name: {1}",i.ToString(),e.Name);

}

Console.WriteLine(g.Manager.Name);

Console.WriteLine(g.GroupID);

Console.WriteLine(g.HexBytes[0]);

}

(3)例子中相关类信息生成的XML文件

<? xml version="1.0" encoding="utf-8" ?>

< Tables xmlns:xsd ="http://www.w3.org/2001/XMLSchema" xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance" >

< Member >

< Employee AHead ="false" >

< Name >Jack </ Name >

< Age >0 </ Age >

< des2 >Yyyy

</ des2 >

< ColumnType LinkField ="Haaa

" />

< ColumnType LinkType ="Zzzz

" />

</ Employee >

< Employee Desc ="OK" AHead ="false" >

< Name >Jill </ Name >

< Age >20 </ Age >

< Age >40 </ Age >

</ Employee >

</ Member >

< Building >10.088999748229981 </ Building >

< HexBytes >64 </ HexBytes >

< IsActive >false </ IsActive >

< Manager Desc ="Yes" AHead ="true" >

< Name >Sara </ Name >

< Age >0 </ Age >

< Level >4 </ Level >

</ Manager >

< ObjectNumber >42 </ ObjectNumber >

< ObjectString >Answer </ ObjectString >

</ Tables >

(4) XML总体框架如何用XML相关属性类描述

public class Tables

{

[XmlArray(ElementName = "Member")]

public Employee[] Employees;

[XmlElement(DataType = "double",

ElementName = "Building")]

public double GroupID;

[XmlElement(DataType = "hexBinary")]

public byte [] HexBytes;

[XmlElement(DataType = "boolean")]

public bool IsActive;

[XmlElement(Type = typeof(Manager))]

public Employee Manager;

[XmlElement(typeof(int),

ElementName = "ObjectNumber"),

XmlElement(typeof(string),

ElementName = "ObjectString")]

public ArrayList ExtraInfo;

}

(5) 类的字段信息表示为属性的方法

public class Employee

{

public string Name;

[XmlElement(typeof(int))]

public int[] Age = new int[2];

[XmlAttribute(AttributeName = "Desc")]

public string Desc;

[XmlAttribute(AttributeName = "AHead")]

public bool aHead;

public string des2;

[XmlElement(ElementName="ColumnType")]

public ColumnType[] colType;

}

2.自己根据需要定义自己的属性类，例如定义相关业务类和UI的关系。
在使用中，信息不是一个UI就完成的，可能经过了几个UI，或者几个页面去交互，但可能业务的调整，显示的位置或者一些参数可能需要调整的，这些UI的信息能否也定义为类的某些属性？
从.NET的Attribute派生一个客户定制类可以轻松做到这点，定制类只需要从System.Attribute派生即可。

[AttributeUsage(AttributeTargets.Field | AttributeTargets.Class,AllowMultiple= true)]

public class LayoutAttribute : Attribute

{

string m_desc;

public string OwnPage;

public string GetDesc()

{

return m_desc;

}

public LayoutAttribute(string strDesc)

{

m_desc = strDesc;

}

AttributeUsage这个类定义了LayoutAttribute的一些基本信息，例如这里定义了LayoutAttribute适用于字段，类，并且允许重复定义的。

在应用中，可以利用反射机制，将这些定义的信息获取，从而判断应该在界面上如何处理了。

Type myType = Type.GetType("testXmlAttr.Manager");

Console.WriteLine(myType.FullName);

FieldInfo myFieldInfo = myType.GetField("Level");

object[] atts = myFieldInfo.GetCustomAttributes( false);

for ( int i=0;i<atts.Length;i++)

Console.WriteLine(((LayoutAttribute)atts[i]).OwnPage);

例子运行结果：（同时在当前目录下生成testXmlAttr.xml）

本文转自风前絮~~博客园博客，原文链接：http://www.cnblogs.com/windsails/archive/2004/09/08/41006.html，如需转载请自行联系原作者

开发中灵活使用属性类

热门文章

最新文章

相关电子书

相关实验场景