如何将参数传递给 C# 中的公共类？

Question

如何将参数传递给 C# 中的公共类。 我是 C# 新手，所以请原谅 n00b 问题。

给定这个示例类：

public class DoSomething
{
    public static void  Main(System.String[] args)
    {

        System.String apple = args[0];
        System.String orange = args[1];
        System.String banana = args[2];
        System.String peach = args[3];

        // do something
    }
}

如何传递请求的参数？

我希望写这样的东西：

DoSomething ds = new DoSomething();
ds.apple = "pie";

但这失败了。

Answer 1

首先，让我们为您的版本添加注释，然后继续您可能想要的内容。

// Here you declare your DoSomething class
public class DoSomething
{
    // now you're defining a static function called Main
    // This function isn't associated with any specific instance
    // of your class. You can invoke it just from the type,
    // like: DoSomething.Main(...)
    public static void Main(System.String[] args)
    {
        // Here, you declare some variables that are only in scope
        // during the Main function, and assign them values 
        System.String apple = args[0];
        System.String orange = args[1];
        System.String banana = args[2];
        System.String peach = args[3];
    }
        // at this point, the fruit variables are all out of scope - they
        // aren't members of your class, just variables in this function.

    // There are no variables out here in your class definition
    // There isn't a constructor for your class, so only the
    // default public one is available: DoSomething()
}

以下是您可能想要的类定义：

public class DoSomething
{
    // The properties of the class.
    public string Apple; 
    public string Orange;

    // A constructor with no parameters
    public DoSomething()
    {
    }

    // A constructor that takes parameter to set the properties
    public DoSomething(string apple, string orange)
    {
        Apple = apple;
        Orange = orange;
    }

}

然后您可以像下面这样创建/操作该类。在每种情况下，实例都会以 Apple = "foo" 和 Orange = "bar" 结束

DoSomething X = new DoSomething("foo", "bar");

DoSomething Y = new DoSomething();
Y.Apple = "foo";
Y.Orange = "bar";

DoSomething Z = new DoSomething()
{
    Apple = "foo",
    Orange = "bar"
};

Answer 2

Main 方法的String[] args 参数在您通过命令行启动应用程序时填充：

/your/application/path/DoSomething.exe arg1 arg2 arg3 ...

如果您想以编程方式传递这些参数，您必须将变量设置为公共属性，例如：

public class DoSomething
{
   public string Apple { get; set; }
   public string Orange { get; set; }
   public string Banana { get; set; }
   // other fruits...
}

那么你可以这样做：

public class Test
{
    public static void  Main(System.String[] args)
    {
        DoSomething ds = new DoSomething();
        ds.Apple = "pie";

        // do something
    }
}

Answer 3

使用公共属性，您可以使用auto-implemented property 开头：

public class DoSomething
{
   public string Apple {get;set;}
}

Answer 4

构造函数：

public class DoSomething
{
    public DoSomething(String mystring) { ... }

    static void Main(String[] args) {
        new DoSomething(args[0]);
    }
}

编辑

注意到 C# 在线书籍是德语的。但我敢肯定也有英文书。

Answer 5

在您提供的示例中，您创建的变量在Main 方法的范围内；它们不是类级别的变量。

您可以通过使它们成为类的成员来访问它们，如下所示：

我原来的代码 sn-p 错了；您的 Main 方法是静态的，因此您无法访问实例变量。

public class DoSomething 
{ 
    public string apple;

    public void Main(System.String[] args) 
    { 
         apple = args[0];
    } 
}