Eine Saite in einen Operator verwandeln

Question

Was ich gerne wissen würde ist, wie man eine Saite in einen Operator verwandelt.

Ich möchte in der Lage sein, einen Wert mit einem anderen zu vergleichen, und die Bedingung, ob es wahr ist oder nicht, ist eine Zeichenfolge. Zum Beispiel könnte die Zeichenfolge ne '>' oder '> =' oder etwas anderes, das ich definieren kann, wie 'GREATER_THAN'.

Ist der beste Weg nur ein Fall oder gibt es etwas besseres mit all den Zaubern von C#?

Answer 1

können Sie diese einfache Methode:

private bool Compare(string operator, int x, int y) 
{ 
    switch (operator) 
    { 
     case ">": return x > y; 
     case "<": return x < y; 
     case "==": return x == y; 
     ... etc.    
    } 
} 

bool result = Compare(">", 6, 8); 

Answer 2

No you cant neue Operatoren definieren, aber wenn man einen Vergleich für ein neues Business-Objekt des eigenen definieren möchten, dann können Sie Benutzer Betreiber Überlastung für Ihre Modell. Finden Sie, wie

https://www.tutorialspoint.com/csharp/csharp_operator_overloading.htm

using System; 
namespace OperatorOvlApplication 
{ 
    class Box 
    { 
     private double length; // Length of a box 
     private double breadth; // Breadth of a box 
     private double height; // Height of a box 

     public double getVolume() 
     { 
     return length * breadth * height; 
     } 

     public void setLength(double len) 
     { 
     length = len; 
     } 

     public void setBreadth(double bre) 
     { 
     breadth = bre; 
     } 


     public void setHeight(double hei) 
     { 
     height = hei; 
     } 

     // Overload + operator to add two Box objects. 
     public static Box operator+ (Box b, Box c) 
     { 
     Box box = new Box(); 
     box.length = b.length + c.length; 
     box.breadth = b.breadth + c.breadth; 
     box.height = b.height + c.height; 
     return box; 
     } 

     public static bool operator == (Box lhs, Box rhs) 
     { 
     bool status = false; 
     if (lhs.length == rhs.length && lhs.height == rhs.height && lhs.breadth == rhs.breadth) 
     { 
      status = true; 
     } 
     return status; 
     } 

     public static bool operator !=(Box lhs, Box rhs) 
     { 
     bool status = false; 
     if (lhs.length != rhs.length || lhs.height != rhs.height || lhs.breadth != rhs.breadth) 
     { 
      status = true; 
     } 
     return status; 
     } 

     public static bool operator <(Box lhs, Box rhs) 
     { 
     bool status = false; 
     if (lhs.length < rhs.length && lhs.height < rhs.height && lhs.breadth < rhs.breadth) 
     { 
      status = true; 
     } 
     return status; 
     } 

     public static bool operator >(Box lhs, Box rhs) 
     { 
     bool status = false; 
     if (lhs.length > rhs.length && lhs.height > rhs.height && lhs.breadth > rhs.breadth) 
     { 
      status = true; 
     } 
     return status; 
     } 

     public static bool operator <=(Box lhs, Box rhs) 
     { 
     bool status = false; 
     if (lhs.length <= rhs.length && lhs.height <= rhs.height && lhs.breadth <= rhs.breadth) 
     { 
      status = true; 
     } 
     return status; 
     } 

     public static bool operator >=(Box lhs, Box rhs) 
     { 
     bool status = false; 
     if (lhs.length >= rhs.length && lhs.height >= rhs.height && lhs.breadth >= rhs.breadth) 
     { 
      status = true; 
     } 
     return status; 
     } 
     public override string ToString() 
     { 
     return String.Format("({0}, {1}, {2})", length, breadth, height); 
     } 
    } 

    class Tester 
    { 
     static void Main(string[] args) 
     { 
     Box Box1 = new Box(); // Declare Box1 of type Box 
     Box Box2 = new Box(); // Declare Box2 of type Box 
     Box Box3 = new Box(); // Declare Box3 of type Box 
     Box Box4 = new Box(); 
     double volume = 0.0; // Store the volume of a box here 

     // box 1 specification 
     Box1.setLength(6.0); 
     Box1.setBreadth(7.0); 
     Box1.setHeight(5.0); 

     // box 2 specification 
     Box2.setLength(12.0); 
     Box2.setBreadth(13.0); 
     Box2.setHeight(10.0); 

     //displaying the Boxes using the overloaded ToString(): 
     Console.WriteLine("Box 1: {0}", Box1.ToString()); 
     Console.WriteLine("Box 2: {0}", Box2.ToString()); 

     // volume of box 1 
     volume = Box1.getVolume(); 
     Console.WriteLine("Volume of Box1 : {0}", volume); 

     // volume of box 2 
     volume = Box2.getVolume(); 
     Console.WriteLine("Volume of Box2 : {0}", volume); 

     // Add two object as follows: 
     Box3 = Box1 + Box2; 
     Console.WriteLine("Box 3: {0}", Box3.ToString()); 

     // volume of box 3 
     volume = Box3.getVolume(); 
     Console.WriteLine("Volume of Box3 : {0}", volume); 

     //comparing the boxes 
     if (Box1 > Box2) 
      Console.WriteLine("Box1 is greater than Box2"); 
     else 
      Console.WriteLine("Box1 is greater than Box2"); 

     if (Box1 < Box2) 
      Console.WriteLine("Box1 is less than Box2"); 
     else 
      Console.WriteLine("Box1 is not less than Box2"); 

     if (Box1 >= Box2) 
      Console.WriteLine("Box1 is greater or equal to Box2"); 
     else 
      Console.WriteLine("Box1 is not greater or equal to Box2"); 

     if (Box1 <= Box2) 
      Console.WriteLine("Box1 is less or equal to Box2"); 
     else 
      Console.WriteLine("Box1 is not less or equal to Box2"); 

     if (Box1 != Box2) 
      Console.WriteLine("Box1 is not equal to Box2"); 
     else 
      Console.WriteLine("Box1 is not greater or equal to Box2"); 
     Box4 = Box3; 

     if (Box3 == Box4) 
      Console.WriteLine("Box3 is equal to Box4"); 
     else 
      Console.WriteLine("Box3 is not equal to Box4"); 

     Console.ReadKey(); 
     } 
    } 
} 

Ansonsten, das hier zu tun, können Sie eine Funktion vergleichen, schreiben die Sie benutzerdefinierte Name des Bedieners und Operanden wie folgt

Answer 3

Etwas nimmt (lassen Sie uns die Lösung verallgemeinern):

private static bool MyCompare<T>(string comparer, T x, T y) where T: IComparable<T> { 
    // we can't put x.CompareTo(y) since either x or y or both can be null 
    int v = Comparer<T>.Default.Compare(x, y); 

    //TODO: you may want strict tests: if (comparer == ">") return v == 0; else if() ... 
    if (comparer.Contains('<') && v < 0) 
    return true; 

    if (comparer.Contains('>') && v > 0) 
    return true; 

    if (comparer.Contains('=') && v == 0) 
    return true; 

    if (comparer.Contains('!') && v != 0) 
    return true; 

    return false; 
} 

Samples:

Console.WriteLine(MyCompare(">", 3, 8) ? "Y" : "N"); 
Console.WriteLine(MyCompare(">=", true, false) ? "Y" : "N"); 
Console.WriteLine(MyCompare("<>", "a", "b") ? "Y" : "N"); // Pascal syntax 
Console.WriteLine(MyCompare("!=", "a", "b") ? "Y" : "N"); // C syntax 
Console.WriteLine(MyCompare("==", 3.4, 7.8) ? "Y" : "N");