[英]How to use switch-case with strings in c#?
I'm trying to make a really basic calculator program. 我正在尝试制作一个非常基本的计算器程序。 I am getting the following error message:
我收到以下错误消息:
Cannot implicitly convert type 'bool' to 'string'
无法将类型'bool'隐式转换为'string'
Here is my code: 这是我的代码:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace _2019_03_21
{
class Program
{
private static double Negyzet(int alap, int kitevo)
{
Console.WriteLine("Kérem a hatvány alapját!");
alap = int.Parse(Console.ReadLine());
Console.WriteLine("Kérem a hatvány kitevojet!");
kitevo = int.Parse(Console.ReadLine());
return Math.Pow(alap, kitevo);
}
static void Main(string[] args)
{
Console.WriteLine("Kérem adja meg milyen műveletet szeretne elvégezni!\n\n+ összeadás\n- kivonás\n* szorzás\n/ osztás\n^hatványozás\n\nVálasztott művelet:");
string muvelet = Console.ReadLine();
switch (muvelet)
{
case (muvelet == "^"): Console.WriteLine("A hatvány értéke: {0}", Negyzet(0, 0)); break;
default: break;
}
Console.ReadKey();
}
}
}
You're using the case
clause in a wrong way. 您以错误的方式使用了
case
子句。 It expects integer or String
values - but you supply a Boolean
value. 它需要整数或
String
值-但是您提供了Boolean
值。 It's easy to fix that, however. 但是,很容易解决该问题。 Just write the
case
clause like that: 像这样写
case
子句:
case "^":
Then it should compile and work as expected. 然后它应该可以按预期进行编译和工作。
muvelet is a string while muvelet == "^"
is a comarision which is boolean (it is either true or false muvelet是一个字符串,而
muvelet == "^"
是一个布尔运算符(它是true或false
switch(muvelet)
{
case "^":
// code for when it is equal to "^"
break;
//other cases
default:
//it is unknown character
}
note that the type in your switch (that is a string in this case) should match the type of cases 请注意,交换机中的类型(在这种情况下为字符串)应与案例的类型匹配
Until C# 6, the switch instruction was reserved for primitive types. 在C#6之前,switch指令是为基本类型保留的。 You can now switch to patterns.
您现在可以切换到模式。
And so you can do that kind of thing : 因此,您可以执行以下操作:
class Program
{
static void Main(string[] args)
{
Print("+", 2, 2);
Print("-", 2, 2);
Print("/", 2, 2);
Print("*", 2, 2);
Print("^", 2, 2);
Print("%", 2, 2);
Print(" ", 2, 2);
Print("", 2, 2);
Console.Read();
}
static void Print(string op, int nmb1, int nmb2)
{
var res = Compute(op, nmb1, nmb2);
Console.WriteLine(res != null ?
$"{nmb1} {op} {nmb2} = {res}" :
$"invalid {op?.Trim()} operator description");
}
static int? Compute(string op,int nmb1,int nmb2)
{
switch (op)
{
case "+":
return nmb1 + nmb2;
case "-":
return nmb1 - nmb2;
case "*":
return nmb1 * nmb2;
case "/":
return nmb1 / nmb2;
case "%":
return nmb1 % nmb2;
case "^":
return nmb1 ^ nmb2;
case var o when (o?.Trim().Length ?? 0) == 0:
// white space
return null;
default:
return null;
}
}
}
console output : 控制台输出:
2 + 2 = 4
2 - 2 = 0
2 / 2 = 1
2 * 2 = 4
2 ^ 2 = 0
2 % 2 = 0
invalid operator
invalid operator
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