в 15:31, 26 мая 2010

2010-05-26T15:31:53Z

Admin: 1 версия

2010-05-26T12:14:29Z

1 версия

Новая страница

==A custom attribute based on bool value==

<source lang="csharp">using System;
public class TrueFalseAttribute : Attribute
{
bool bWritten;
public bool Written()
{
return bWritten;
}
public TrueFalseAttribute(bool Written)
{
bWritten = Written;
}
}
[TrueFalseAttribute(true)]
public class Class1
{
}
[TrueFalseAttribute(false)]
public class Class2
{
}
class MainClass
{
public static void Main()
{
TrueFalseAttribute u;
Console.Write("Class1 TrueFalseAttribute attribute: ");
u = (TrueFalseAttribute) Attribute.GetCustomAttribute(typeof(Class1), typeof(TrueFalseAttribute));
Console.WriteLine(u.Written());
Console.Write("Class2 TrueFalseAttribute attribute: ");
u = (TrueFalseAttribute) Attribute.GetCustomAttribute(typeof(Class2), typeof(TrueFalseAttribute));
Console.WriteLine(u.Written());
}
}</source>
<pre class=codeResult>Class1 TrueFalseAttribute attribute: True
Class2 TrueFalseAttribute attribute: False</pre>

==Assembly level attributes don"t have to be in the assemblyinfo.cs file, but must be lised outside of any namespae definition.==

<source lang="csharp">using System;
[assembly:System.CLSCompliantAttribute(true)]
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct)]
public class MyDescriptionAttribute : System.Attribute
{
private string description;
public string Desc
{
get { return description; }
set { description = value; }
}
public MyDescriptionAttribute() {}
public MyDescriptionAttribute(string desc)
{ description = desc;}
}

[MyDescriptionAttribute("Info")]
public class MyClass
{
public MyClass()
{
}
}

public class MainClass
{
public static int Main(string[] args)
{
Type t = typeof(MyClass);

// Get all attributes in the assembly.
object[] customAtts = t.GetCustomAttributes(false);

// List all info.
Console.WriteLine("Value of MyDescriptionAttribute");
foreach(MyDescriptionAttribute v in customAtts)
Console.WriteLine("-> {0}\n", v.Desc);
return 0;
}
}</source>
<pre class=codeResult>Value of MyDescriptionAttribute
-> Info</pre>

==Attribute with supplement information==

<source lang="csharp">using System;
[AttributeUsage(AttributeTargets.All)]
public class MyAttribute : Attribute {
string remark;

public string supplement;

public MyAttribute(string comment) {
remark = comment;
supplement = "None";
}

}</source>

==Create Attribute==

<source lang="csharp">using System;
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Assembly, AllowMultiple = true, Inherited = false)]
public class AuthorAttribute : System.Attribute
{
public string Company;
public string Name;
public AuthorAttribute(string name)
{
this.Name = name;
Company = "";
}
}

[Author("Name1")]
[Author("Name2", Company = "Ltd.")]
class MainClass
{
public static void Main()
{
Type type = typeof(MainClass);
object[] attrs = type.GetCustomAttributes(typeof(AuthorAttribute), true);
foreach (AuthorAttribute a in attrs)
{
Console.WriteLine(a.Name + ", " + a.rupany);
}
}
}</source>
<pre class=codeResult>Name2, Ltd.
Name1,</pre>

==Positional vs. Named Parameters==

<OL><LI>A positional parameter is linked by its position.</LI><LI>Positional parameters must be specified in the order in which they appear.</LI><LI>Named parameters are specified by assigning values to their names.</LI><LI>For an attribute, you can also create named parameters</LI><LI>named parameters can be assigned initial values by using their names.</LI><LI>A named parameter is supported by either a public field or property, which must not be read-only.</LI></OL>
<p>Here is the general form of an attribute specification that includes named parameters:</p>

<source lang="csharp">[attrib(positional-param-list, named-param1 = value, named-param2 = value, ...)]</source>

==Use a named attribute parameter.==

<source lang="csharp">using System;
using System.Reflection;

[AttributeUsage(AttributeTargets.All)]
public class MyAttribute : Attribute {
public string remark;

public string supplement;

public MyAttribute(string comment) {
remark = comment;
supplement = "None";
}

public string Remark {
get {
return remark;
}
}
}

[MyAttribute("This class uses an attribute.",
supplement = "This is additional info.")]
class UseAttrib {
}

class MainClass {
public static void Main() {
Type t = typeof(UseAttrib);

Console.Write("Attributes in " + t.Name + ": ");

object[] attribs = t.GetCustomAttributes(false);
foreach(object o in attribs) {
Console.WriteLine(o);
}

// Retrieve the MyAttribute.
Type tRemAtt = typeof(MyAttribute);
MyAttribute ra = (MyAttribute)
Attribute.GetCustomAttribute(t, tRemAtt);

Console.Write("Remark: ");
Console.WriteLine(ra.remark);

Console.Write("Supplement: ");
Console.WriteLine(ra.supplement);
}
}</source>
<pre class=codeResult>Attributes in UseAttrib: MyAttribute
Remark: This class uses an attribute.
Supplement: This is additional info.</pre>

==Use a property as a named attribute parameter.==

<source lang="csharp">using System;
using System.Reflection;

[AttributeUsage(AttributeTargets.All)]
public class MyAttribute : Attribute {
public string remark;

public int priority;

public string supplement;

public MyAttribute(string comment) {
remark = comment;
supplement = "None";
}

public string Remark {
get {
return remark;
}
}

public int Priority {
get {
return priority;
}
set {
priority = value;
}
}
}

[MyAttribute("This class uses an attribute.",
supplement = "This is additional info.",
Priority = 10)]
class UseAttrib {
}

class MainClass {
public static void Main() {
Type t = typeof(UseAttrib);

Console.Write("Attributes in " + t.Name + ": ");

object[] attribs = t.GetCustomAttributes(false);
foreach(object o in attribs) {
Console.WriteLine(o);
}

// Retrieve the MyAttribute.
Type tRemAtt = typeof(MyAttribute);
MyAttribute ra = (MyAttribute)
Attribute.GetCustomAttribute(t, tRemAtt);

Console.Write("Remark: ");
Console.WriteLine(ra.remark);

Console.Write("Supplement: ");
Console.WriteLine(ra.supplement);

Console.WriteLine("Priority: " + ra.priority);
}
}</source>
<pre class=codeResult>Attributes in UseAttrib: MyAttribute
Remark: This class uses an attribute.
Supplement: This is additional info.
Priority: 10</pre>

← Предыдущая	Версия 15:31, 26 мая 2010
(нет различий)

Csharp/CSharp Tutorial/Attribute/Attribute Definition - История изменений

в 15:31, 26 мая 2010

Admin: 1 версия