自定义控件

基元属性

以下示例定义了名为 Number 的基元属性。
[C#]
private int number = 0;
[Description("A nonnegative integer")]
public int Number
{
    get
    {
        if (number < 0) return 0;
        return number;
    }
    set
    {
        if (value < 0) number = 0;
        else number = value;
    }
}

枚举属性

当属性是枚举类型时，定义该属性类型的语法与其他基元属性类型的语法相同；但是，设置属性的页语法是不同的。以下代码片段定义了名为 Position 的枚举类型。
[C#]
public enum Position
{
    Forward = 0,
    Mid = 1,
    Defence = 2,
    Goalee = 3,
}

以下代码片段说明了公布 Position 类型属性的一个控件 (SoccerPlayer)。
[C#]
public class SoccerPlayer : Control
{ 
    private Position position;
    ...
    // PlayerPosition is an enumeration property whose
    // type is the Position enumeration.
    [Description("The position of the player on the field.")]
    public Position PlayerPosition
    {
        get
        {
            return position;
        }
        set
        {
            position = value;
        }
    }
    ...
}

类属性

如果类 A 有一个类型为类 B 的属性，则 B 的属性（如果有）称为 A 的子属性。

以下代码片段定义了名为 Address 的类，它公开四个属性，每个属性的类型均为 String。

[C#] // The Address class. 

public class Address

{

    private string street = null;

    private string city = null;

    private string state = null;

    private string zip = null;

    // The Street property. 

    public string Street

    {

        get{...}

        set{...}

    } 

    // The City property. 

    public string City

    {

        get{...}

        set{...}

    }

    // The State property. 

    public string State

    {

        get{...}

        set{...}

    }

    // The Zip property. 

    public string Zip

    {

        get{...}

        set{...}

    }

}

以下代码片段定义了名为 SoccerPlayer 的控件，它公开了一个类型为类 Address 的属性。
       

       
       
[C#] public class SoccerPlayer : Control 

{

    private Address address = new Address();

    // PlayerAddress is complex property whose

    // type is the class Address. Address has four

    // properties, Street, City, State, and Zip. These become

    // subproperties of SoccerPlayer.

    public Address PlayerAddress

    {

        get

        {

            return address;

        }

        // Note that the set accessor is not defined.

        // The get accessor provides a handle to a PlayerAddress

        // instance that can be used to set a subproperty such as

        // PlayerAddress.Street.

    }

}