C# 将变量与多个值进行比较
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Comparing a variable to multiple values
提问by Mongus Pong
Quite often in my code I need to compare a variable to several values :
在我的代码中，我经常需要将一个变量与多个值进行比较：
if ( type == BillType.Bill || type == BillType.Payment || type == BillType.Receipt )
{
// Do stuff
}
I keep on thinking I can do :
我一直认为我可以做到：
if ( type in ( BillType.Bill, BillType.Payment, BillType.Receipt ) )
{
// Do stuff
}
But of course thats SQL that allows this.
但当然这就是允许这样做的 SQL。
Is there a tidier way in C#?
C# 中有更整洁的方法吗？
采纳答案by Mark
You could do with with .Contains like this:
你可以用 .Contains 做这样的事情：
if(new[]{BillType.Receipt,BillType.Bill,BillType.Payment}.Contains(type)){}
Or, create your own extension method that does it with a more readable syntax
或者，创建您自己的扩展方法，使用更易读的语法来完成它
public static class MyExtensions
{
public static bool IsIn<T>(this T @this, params T[] possibles)
{
return possibles.Contains(@this);
}
}
Then call it by:
然后通过以下方式调用它：
if(type.IsIn(BillType.Receipt,BillType.Bill,BillType.Payment)){}
回答by Sergiy Belozorov
Try using C# HashSet for list of values. This can be especially useful if you need to compare many values to single set of values.
尝试使用 C# HashSet 获取值列表。如果您需要将多个值与一组值进行比较，这将特别有用。
回答by Yuriy Faktorovich
Assuming type is an enumeration, you could use the FlagsAttribute:
假设 type 是枚举，您可以使用FlagsAttribute：
[Flags]
enum BillType
{
None = 0,
Bill = 2,
Payment = 4,
Receipt = 8
}
if ((type & (BillType.Bill | BillType.Payment | BillType.Receipt)) != 0)
{
//do stuff
}
回答by Jarrett Meyer
Try checking out the Strategy Design Pattern (a.k.a. the Policy Design Pattern).
尝试查看策略设计模式（又名策略设计模式）。
public interface IBillTypePolicy
{
public BillType { get; }
void HandleBillType();
}
public class BillPolicy : IBillTypePolicy
{
public BillType BillType { get { return BillType.Bill; } }
public void HandleBillType()
{
// your code here...
}
}
Here's a great post on how to dynamically resolve the policyfrom Los Techies.
回答by wasatz
There's also the switch statement
还有 switch 语句
switch(type) {
case BillType.Bill:
case BillType.Payment:
case BillType.Receipt:
// Do stuff
break;
}
回答by bleeeah
Try using a switch
尝试使用开关
switch (type)
{
case BillType.Bill:
case BillType.Payment:
break;
}
回答by p.marino
What about getting an array of all Enums values and iterate through this?
获取所有枚举值的数组并遍历它怎么样？
http://maniish.wordpress.com/2007/09/27/iterate-through-enumeration-c/
http://maniish.wordpress.com/2007/09/27/iterate-through-enumeration-c/
