网上到处充斥这c#与java对比的文章，看了看，还是觉的MSDN上的一篇文章很全面和客观。《
针对JAVA开发人员的C#编程语言》。
我的第一天C#学习，总体感觉C#在语言层面上保留了更多C++/C的特点，比如virtual,override关键字的使用，比如结构（值类型，存储在栈上），比如delegate（类似函数指针）。比较感兴趣的也就是delegate、事件和attribute方面。C#某种意义上讲比java稍微复杂，比C++简单。
参照语言规范写的例子，抽象类、继承的例子，可以扩展成一个简单计算器：
再来一个委托的例子，函数作为变量的传递和使用，对有C++经验或者动态语言经验的人来说不会奇怪：
我的第一天C#学习，总体感觉C#在语言层面上保留了更多C++/C的特点，比如virtual,override关键字的使用，比如结构（值类型，存储在栈上），比如delegate（类似函数指针）。比较感兴趣的也就是delegate、事件和attribute方面。C#某种意义上讲比java稍微复杂，比C++简单。
参照语言规范写的例子，抽象类、继承的例子，可以扩展成一个简单计算器：
using
System;
using System.Collections;
namespace VirtualDemo
{
public abstract class Expression
{
public abstract double Evaluate(Hashtable vars);
}
public class Constant : Expression
{
double value;
public Constant( double value)
{
this .value = value;
}
public override double Evaluate(Hashtable vars)
{
return value;
}
}
public class VariableReference : Expression
{
string name;
public VariableReference( string name)
{
this .name = name;
}
public override double Evaluate(Hashtable vars)
{
object value = vars[name];
if (value == null )
{
throw new Exception( " Unknown variable: " + name);
}
return Convert.ToDouble(value);
}
}
public class Operation : Expression
{
Expression left;
char op;
Expression right;
public Operation(Expression left, char op, Expression right)
{
this .left = left;
this .op = op;
this .right = right;
}
public override double Evaluate(Hashtable vars)
{
double x = left.Evaluate(vars);
double y = right.Evaluate(vars);
switch (op)
{
case ' + ' : return x + y;
case ' - ' : return x - y;
case ' * ' : return x * y;
case ' / ' : return x / y;
}
throw new Exception( " Unknown operator " );
}
}
public class Test
{
public static void Main( string []args)
{
Expression e = new Operation(
new VariableReference( " x " ),
' * ' ,
new Operation(
new VariableReference( " y " ),
' + ' ,
new Constant( 2 )
)
);
Hashtable vars = new Hashtable();
vars[ " x " ] = 3 ;
vars[ " y " ] = 5 ;
Console.WriteLine(e.Evaluate(vars)); // Outputs "21"
vars[ " x " ] = 1.5 ;
vars[ " y " ] = 9 ;
Console.WriteLine(e.Evaluate(vars)); // Outputs "16.5"
}
}
}
using System.Collections;
namespace VirtualDemo
{
public abstract class Expression
{
public abstract double Evaluate(Hashtable vars);
}
public class Constant : Expression
{
double value;
public Constant( double value)
{
this .value = value;
}
public override double Evaluate(Hashtable vars)
{
return value;
}
}
public class VariableReference : Expression
{
string name;
public VariableReference( string name)
{
this .name = name;
}
public override double Evaluate(Hashtable vars)
{
object value = vars[name];
if (value == null )
{
throw new Exception( " Unknown variable: " + name);
}
return Convert.ToDouble(value);
}
}
public class Operation : Expression
{
Expression left;
char op;
Expression right;
public Operation(Expression left, char op, Expression right)
{
this .left = left;
this .op = op;
this .right = right;
}
public override double Evaluate(Hashtable vars)
{
double x = left.Evaluate(vars);
double y = right.Evaluate(vars);
switch (op)
{
case ' + ' : return x + y;
case ' - ' : return x - y;
case ' * ' : return x * y;
case ' / ' : return x / y;
}
throw new Exception( " Unknown operator " );
}
}
public class Test
{
public static void Main( string []args)
{
Expression e = new Operation(
new VariableReference( " x " ),
' * ' ,
new Operation(
new VariableReference( " y " ),
' + ' ,
new Constant( 2 )
)
);
Hashtable vars = new Hashtable();
vars[ " x " ] = 3 ;
vars[ " y " ] = 5 ;
Console.WriteLine(e.Evaluate(vars)); // Outputs "21"
vars[ " x " ] = 1.5 ;
vars[ " y " ] = 9 ;
Console.WriteLine(e.Evaluate(vars)); // Outputs "16.5"
}
}
}
再来一个委托的例子，函数作为变量的传递和使用，对有C++经验或者动态语言经验的人来说不会奇怪：
using
System;
namespace DelegateDemo
{
delegate double Function( double x);
class Multiplier
{
double factor;
public Multiplier( double factor)
{
this .factor = factor;
}
public double Multiply( double x)
{
return x * factor;
}
}
class Test
{
static double Square( double x)
{
return x * x;
}
static double [] Apply( double [] a, Function f)
{
double [] result = new double [a.Length];
//直接通过f()调用
for ( int i = 0 ; i < a.Length; i ++ ) result[i] = f(a[i]);
return result;
}
static void Main()
{
double [] a = { 0.0 , 0.5 , 1.0 };
//delegate Function分别赋予了不同的方法
double [] squares = Apply(a, new Function(Square));
double [] sines = Apply(a, new Function(Math.Sin));
Multiplier m = new Multiplier( 2.0 );
double [] doubles = Apply(a, new Function(m.Multiply));
foreach ( double b in doubles)
{
Console.WriteLine(b);
}
}
}
}
namespace DelegateDemo
{
delegate double Function( double x);
class Multiplier
{
double factor;
public Multiplier( double factor)
{
this .factor = factor;
}
public double Multiply( double x)
{
return x * factor;
}
}
class Test
{
static double Square( double x)
{
return x * x;
}
static double [] Apply( double [] a, Function f)
{
double [] result = new double [a.Length];
//直接通过f()调用
for ( int i = 0 ; i < a.Length; i ++ ) result[i] = f(a[i]);
return result;
}
static void Main()
{
double [] a = { 0.0 , 0.5 , 1.0 };
//delegate Function分别赋予了不同的方法
double [] squares = Apply(a, new Function(Square));
double [] sines = Apply(a, new Function(Math.Sin));
Multiplier m = new Multiplier( 2.0 );
double [] doubles = Apply(a, new Function(m.Multiply));
foreach ( double b in doubles)
{
Console.WriteLine(b);
}
}
}
}
文章转自庄周梦蝶 ，原文发布时间5.17
