كيف أقوم بعمل Overload للمعامل == أو = أو !=

 

[color= #666666; font-style: italic;]//Copyright © Microsoft Corporation.  All rights reserved.

 

[color= #666666; font-style: italic;]// dbbool.cs

using System;

 

public [color= #993333;]struct DBBool

[color= #009900;]{

   [color= #666666; font-style: italic;]// The three possible DBBool values:

   public [color= #993333;]static readonly DBBool dbNull [color= #339933;]= new DBBool[color= #009900;]([color= #cc66cc;]0[color= #009900;]);

   public [color= #993333;]static readonly DBBool dbFalse [color= #339933;]= new DBBool[color= #009900;]([color= #cc66cc;]-1[color= #009900;]);

   public [color= #993333;]static readonly DBBool dbTrue [color= #339933;]= new DBBool[color= #009900;]([color= #cc66cc;]1[color= #009900;]);

   [color= #666666; font-style: italic;]// Private field that stores -1, 0, 1 for dbFalse, dbNull, dbTrue:

   [color= #993333;]int value; 

 

   [color= #666666; font-style: italic;]// Private constructor. The value parameter must be -1, 0, or 1:

   DBBool[color= #009900;]([color= #993333;]int value[color= #009900;]) 

   [color= #009900;]{

      this.[color= #202020;]value [color= #339933;]= value;

   [color= #009900;]}

 

   [color= #666666; font-style: italic;]// Implicit conversion from bool to DBBool. Maps true to 

   [color= #666666; font-style: italic;]// DBBool.dbTrue and false to DBBool.dbFalse:

   public [color= #993333;]static implicit operator DBBool[color= #009900;](bool x[color= #009900;]) 

   [color= #009900;]{

      [color= #b1b100;]return x? dbTrue[color= #339933;]: dbFalse;

   [color= #009900;]}

 

   [color= #666666; font-style: italic;]// Explicit conversion from DBBool to bool. Throws an 

   [color= #666666; font-style: italic;]// exception if the given DBBool is dbNull, otherwise returns

   [color= #666666; font-style: italic;]// true or false:

   public [color= #993333;]static explicit operator bool[color= #009900;](DBBool x[color= #009900;]) 

   [color= #009900;]{

      [color= #b1b100;]if [color= #009900;](x.[color= #202020;]value [color= #339933;]== [color= #cc66cc;]0[color= #009900;]) throw new InvalidOperationException[color= #009900;]([color= #009900;]);

      [color= #b1b100;]return x.[color= #202020;]value > [color= #cc66cc;]0;

   [color= #009900;]}

 

   [color= #666666; font-style: italic;]// Equality operator. Returns dbNull if either operand is dbNull, 

   [color= #666666; font-style: italic;]// otherwise returns dbTrue or dbFalse:

   public [color= #993333;]static DBBool operator [color= #339933;]==[color= #009900;](DBBool x, DBBool y[color= #009900;]) 

   [color= #009900;]{

      [color= #b1b100;]if [color= #009900;](x.[color= #202020;]value [color= #339933;]== [color= #cc66cc;]0 || y.[color= #202020;]value [color= #339933;]== [color= #cc66cc;]0[color= #009900;]) [color= #b1b100;]return dbNull;

      [color= #b1b100;]return x.[color= #202020;]value [color= #339933;]== y.[color= #202020;]value? dbTrue[color= #339933;]: dbFalse;

   [color= #009900;]}

 

   [color= #666666; font-style: italic;]// Inequality operator. Returns dbNull if either operand is

   [color= #666666; font-style: italic;]// dbNull, otherwise returns dbTrue or dbFalse:

   public [color= #993333;]static DBBool operator [color= #339933;]!=[color= #009900;](DBBool x, DBBool y[color= #009900;]) 

   [color= #009900;]{

      [color= #b1b100;]if [color= #009900;](x.[color= #202020;]value [color= #339933;]== [color= #cc66cc;]0 || y.[color= #202020;]value [color= #339933;]== [color= #cc66cc;]0[color= #009900;]) [color= #b1b100;]return dbNull;

      [color= #b1b100;]return x.[color= #202020;]value [color= #339933;]!= y.[color= #202020;]value? dbTrue[color= #339933;]: dbFalse;

   [color= #009900;]}

 

   [color= #666666; font-style: italic;]// Logical negation operator. Returns dbTrue if the operand is 

   [color= #666666; font-style: italic;]// dbFalse, dbNull if the operand is dbNull, or dbFalse if the

   [color= #666666; font-style: italic;]// operand is dbTrue:

   public [color= #993333;]static DBBool operator [color= #339933;]![color= #009900;](DBBool x[color= #009900;]) 

   [color= #009900;]{

      [color= #b1b100;]return new DBBool[color= #009900;]([color= #339933;]-x.[color= #202020;]value[color= #009900;]);

   [color= #009900;]}

 

   [color= #666666; font-style: italic;]// Logical AND operator. Returns dbFalse if either operand is 

   [color= #666666; font-style: italic;]// dbFalse, dbNull if either operand is dbNull, otherwise dbTrue:

   public [color= #993333;]static DBBool operator [color= #339933;]&[color= #009900;](DBBool x, DBBool y[color= #009900;]) 

   [color= #009900;]{

      [color= #b1b100;]return new DBBool[color= #009900;](x.[color= #202020;]value < y.[color= #202020;]value? x.[color= #202020;]value[color= #339933;]: y.[color= #202020;]value[color= #009900;]);

   [color= #009900;]}

 

   [color= #666666; font-style: italic;]// Logical OR operator. Returns dbTrue if either operand is 

   [color= #666666; font-style: italic;]// dbTrue, dbNull if either operand is dbNull, otherwise dbFalse:

   public [color= #993333;]static DBBool operator |[color= #009900;](DBBool x, DBBool y[color= #009900;]) 

   [color= #009900;]{

      [color= #b1b100;]return new DBBool[color= #009900;](x.[color= #202020;]value > y.[color= #202020;]value? x.[color= #202020;]value[color= #339933;]: y.[color= #202020;]value[color= #009900;]);

   [color= #009900;]}

 

   [color= #666666; font-style: italic;]// Definitely true operator. Returns true if the operand is 

   [color= #666666; font-style: italic;]// dbTrue, false otherwise:

   public [color= #993333;]static bool operator [color= #000000; font-weight: bold;]true[color= #009900;](DBBool x[color= #009900;]) 

   [color= #009900;]{

      [color= #b1b100;]return x.[color= #202020;]value > [color= #cc66cc;]0;

   [color= #009900;]}

 

   [color= #666666; font-style: italic;]// Definitely false operator. Returns true if the operand is 

   [color= #666666; font-style: italic;]// dbFalse, false otherwise:

   public [color= #993333;]static bool operator [color= #000000; font-weight: bold;]false[color= #009900;](DBBool x[color= #009900;]) 

   [color= #009900;]{

      [color= #b1b100;]return x.[color= #202020;]value < [color= #cc66cc;]0;

   [color= #009900;]}

 

   [color= #666666; font-style: italic;]// Overload the conversion from DBBool to string:

   public [color= #993333;]static implicit operator [color= #993333;]string[color= #009900;](DBBool x[color= #009900;]) 

   [color= #009900;]{

      [color= #b1b100;]return x.[color= #202020;]value > [color= #cc66cc;]0 ? [color= #ff0000;]"dbTrue"

           [color= #339933;]: x.[color= #202020;]value < [color= #cc66cc;]0 ? [color= #ff0000;]"dbFalse"

           [color= #339933;]: [color= #ff0000;]"dbNull";

   [color= #009900;]}

 

   [color= #666666; font-style: italic;]// Override the Object.Equals(object o) method:

   public override bool Equals[color= #009900;](object o[color= #009900;]) 

   [color= #009900;]{

      try 

      [color= #009900;]{

         [color= #b1b100;]return [color= #009900;](bool[color= #009900;]) [color= #009900;](this [color= #339933;]== [color= #009900;](DBBool[color= #009900;]) o[color= #009900;]);

      [color= #009900;]}

      catch 

      [color= #009900;]{

         [color= #b1b100;]return [color= #000000; font-weight: bold;]false;

      [color= #009900;]}

   [color= #009900;]}

 

   [color= #666666; font-style: italic;]// Override the Object.GetHashCode() method:

   public override [color= #993333;]int GetHashCode[color= #009900;]([color= #009900;]) 

   [color= #009900;]{

      [color= #b1b100;]return value;

   [color= #009900;]}

 

   [color= #666666; font-style: italic;]// Override the ToString method to convert DBBool to a string:

   public override [color= #993333;]string ToString[color= #009900;]([color= #009900;]) 

   [color= #009900;]{

      [color= #b1b100;]switch [color= #009900;](value[color= #009900;]) 

      [color= #009900;]{

         [color= #b1b100;]case [color= #cc66cc;]-1[color= #339933;]:

            [color= #b1b100;]return [color= #ff0000;]"DBBool.False";

         [color= #b1b100;]case [color= #cc66cc;]0[color= #339933;]:

            [color= #b1b100;]return [color= #ff0000;]"DBBool.Null";

         [color= #b1b100;]case [color= #cc66cc;]1[color= #339933;]:

            [color= #b1b100;]return [color= #ff0000;]"DBBool.True";

         [color= #b1b100;]default[color= #339933;]:

            throw new InvalidOperationException[color= #009900;]([color= #009900;]);

      [color= #009900;]}

   [color= #009900;]}

[color= #009900;]}

 

class Test 

[color= #009900;]{

   [color= #993333;]static [color= #993333;]void Main[color= #009900;]([color= #009900;]) 

   [color= #009900;]{

      DBBool a, b;

      a [color= #339933;]= DBBool.[color= #202020;]dbTrue;

      b [color= #339933;]= DBBool.[color= #202020;]dbNull;

 

      Console.[color= #202020;]WriteLine[color= #009900;]( [color= #ff0000;]"!{0} = {1}", a, [color= #339933;]!a[color= #009900;]);

      Console.[color= #202020;]WriteLine[color= #009900;]( [color= #ff0000;]"!{0} = {1}", b, [color= #339933;]!b[color= #009900;]);

      Console.[color= #202020;]WriteLine[color= #009900;]( [color= #ff0000;]"{0} & {1} = {2}", a, b, a [color= #339933;]& b[color= #009900;]);

      Console.[color= #202020;]WriteLine[color= #009900;]( [color= #ff0000;]"{0} | {1} = {2}", a, b, a | b[color= #009900;]);

      [color= #666666; font-style: italic;]// Invoke the true operator to determine the Boolean 

      [color= #666666; font-style: italic;]// value of the DBBool variable:

      [color= #b1b100;]if [color= #009900;](b[color= #009900;])

         Console.[color= #202020;]WriteLine[color= #009900;]([color= #ff0000;]"b is definitely true"[color= #009900;]);

      [color= #b1b100;]else

         Console.[color= #202020;]WriteLine[color= #009900;]([color= #ff0000;]"b is not definitely true"[color= #009900;]);   

   [color= #009900;]}

[color= #009900;]}