如何计算C＃中的通用数字？ [英] How to sum generic numbers in C#?

问题描述

可能存在重复：

正如你在下面的代码中看到的那样，我需要计算两个通用数字的总和。

  public class NumberContainer< T> 
 {
 public T ValueA {get;私人设置; } 
 public T ValueB {get;私人设置; } 
 public T Total {get {return ValueA + ValueB; }} 
} 
  

然而，不可能直接添加两个T值，这会导致编译器错误如下：

lockquote

运算符'+'不能应用于'T'类型的操作数和' T'

鉴于我不打算将T用于除表示数字的值类型（short，ushort， int，uint等），我怎么能执行这个和？ （效率是一个需要考虑的因素）

解决方案

你可以用LINQ的小魔术来做：

  private static readonly Func< T，T，T>加法器; 
 static NumberContainer（）{
 var p1 = Expression.Parameter（typeof（T））; 
 var p2 = Expression.Parameter（typeof（T））; 
 adder =（Func ）表达式
 .Lambda（Expression.Add（p1，p2），p1，p2）
 .Compile（）; 
} 
 public T Total {get {return adder（ValueA，ValueB）; }} 
  

唯一的缺点是这段代码会编译，即使 NumberContainer 使用不支持加法的类型 T 进行实例化;当然它会在运行时抛出异常。另外一个好处是，这个应该用于用户定义的 + 运算符。

Possible Duplicate:
C# generic constraint for only integers

As you can see in the following code, I need to compute the sum of two generic numbers.

public class NumberContainer<T>
{
    public T ValueA { get; private set; }
    public T ValueB { get; private set; }
    public T Total { get { return ValueA + ValueB; } }
}

However, it isn't possible to do a direct addition of the two T values, which results in the compiler error below :

Operator '+' cannot be applied to operands of type 'T' and 'T'

Given that I don't intend to use T for anything else than value-types that represent numbers (short, ushort, int, uint, etc), how could I perform the sum? (efficiency is a factor to be considered)

解决方案

You can do it with "little magic" from LINQ:

private static readonly Func<T, T, T> adder;
static NumberContainer() {
    var p1 = Expression.Parameter(typeof (T));
    var p2 = Expression.Parameter(typeof (T));
    adder = (Func<T, T, T>)Expression
        .Lambda(Expression.Add(p1, p2), p1, p2)
        .Compile();
} 
public T Total { get { return adder(ValueA, ValueB); } }

The only drawback is that this code will compile even if NumberContainer is instantiated with a type T that does not support addition; of course it will throw an exception at run-time. An added benefit is that this should work with user-defined + operators.

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