如何在C#中的一个类的多个实例之间共享一个值

    class Program
{
    static void Main(string[] args)
    {
        string someCommonVarialble = @"c:'some'path'where'the'xmlData'are'stored";
        // create some steel shapes
        SteelBeamShape myBeam1 = new SteelBeamShape("W6x9");
        SteelBeamShape myBeam2 = new SteelBeamShape("W10x22");
        SteelPipeShape myPipe1 = new SteelPipeShape("10odx.375wall");
        SteelPipeShape myPipe2 = new SteelPipeShape("24odx.750wall");
        // do some work with objects here
    }
}
public class SteelBeamShape
{
    // constructor
    public SteelBeamShape(string SteelBeamNominalValue)
    {
        // look up some properties base on nominal value in XML tables
        this.xmlDataPath = someCommonVariable;
        // do stuff .... 
    }
}
public class SteelPipeShape
{
    // constructor
    public SteelPipeShape(string SteelPipeNominalValue)
    {
        // look up some properties base on nominal value in XML tables
        this.xmlDataPath = someCommonVariable;
        // do stuff .... 
    }
}

我会考虑先加载xml数据，然后通过构造函数或将数据发送到类中执行实际工作的方法。

否则，类中可能有重复的代码在做基本相同的事情（加载数据、查找xml数据等）。

要在不同的类之间共享一个公共值，需要从一个公共祖先派生这些类。在您的情况下，您可以定义

public class SteelShape
{
     public static string commonPath {get;set;}
     ... add other common functionality ....
     ... for example, how to load the xml file ....
     public static XDocument LoadData(string fileName)
     {
       ......
     }
}

然后你的类从这个基类派生

public class SteelPipeShape : SteelShape
{
   ....
}

每当您需要引用类实例共享的公共变量时，您都可以使用祖先类名来引用它

 SteelShape.commonPath;

所以综合起来你就有了

void Main()
{
    // Set the path once and for all
    SteelShape.commonPath = @"d:'temp";
    SteelBeamShape myBeam1 = new SteelBeamShape("W6x9");
    SteelBeamShape myBeam2 = new SteelBeamShape("W10x22");
    SteelPipeShape myPipe1 = new SteelPipeShape("10odx.375wall");
    SteelPipeShape myPipe2 = new SteelPipeShape("24odx.750wall");
}
public abstract class SteelShape
{
     public static string commonPath {get;set;}
     public static XDocument LoadData(string fileName)
     {
       ......
     }
}
public class SteelPipeShape : SteelShape
{
    public SteelBeamShape(string SteelBeamNominalValue)
    {
        this.xmlDataPath = SteelShape.commonPath;
        XDocument doc = SteelShape.LoadData("steelbeamshape.xml");
        // do stuff .... 
    }
}
public class SteelBeamShape : SteelShape
{
    public SteelPipeShape(string SteelPipeNominalValue)
    {
        // look up some properties base on nominal value in XML tables
        this.xmlDataPath = SteelShape.commonPath;
        XDocument doc = SteelShape.LoadData("steelpipeshape.xml");
        // do stuff .... 
    }
}

您可以通过从公共基类继承所有Shape类并在基类中将公共变量定义为protected static或public static来实现这一点。

public abstract class BaseShape
{
    public static string mSomeVar = "SomeValue";
}
public class SteelBeamShape : BaseShape
{
    // constructor
    public SteelBeamShape(string SteelBeamNominalValue)
    {
        // look up some properties base on nominal value in XML tables
        this.xmlDataPath = this.mSomeVar;
        // do stuff .... 
    }
}
public class SteelPipeShape : BaseShape
{
    // constructor
    public SteelPipeShape(string SteelPipeNominalValue)
    {
        // look up some properties base on nominal value in XML tables
        this.xmlDataPath = this.mSomeVar;
        // do stuff .... 
    }    
}

public class Lib
{
    private static string _commonVarialble;
    public static string CommonVarialble
    {
        get { return _commonVarialble; }
        set { _commonVarialble = value; }
    }
    public class SteelBeamShape
    {
        // constructor
        public SteelBeamShape(string steelBeamNominalValue)
        {
            // look up some properties base on nominal value in XML tables
            this.xmlDataPath = CommonVarialble;
            // do stuff .... 
        }
    }
}