C -- switch case statement

c#——switch case sentence

c# Medium switch case There are three structures in a sentence , The specific form is shown in the figure below ：

（1）Switch The first structure of ：（ For example 1）

switch(i)

case 1:

//

break;

case2:

//

break;

example 1

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namespace Switch
{
class Program
{
static void Main(string[] args)
{
int i = 2;
switch(i)
{
case 2:
Console.WriteLine(“ You really are 2！”);
Console.WriteLine(“ You are so talented ！”);
break;
case 4:
Console.WriteLine(“ Go to hell. ！”);
break;
case 8:
Console.WriteLine(“ Hair. Hair ！”);
break;
}
Console.ReadKey();
}
}
}

（2）Switch The second structure of ：

switch(i)

case 1:

//

break;

case2:

//

break;

default:

//

break;

example 2

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namespace Switch
{
class Program
{
static void Main(string[] args)
{
int i = 9;
switch(i)
{
case 2: // amount to if(if==2)
Console.WriteLine(“ You really are 2！”);
Console.WriteLine(“ You are so talented ！”);
break; //C# You have to write break
case 4:
Console.WriteLine(“ Go to hell. ！”);
break;
case 8:
Console.WriteLine(“ Hair. Hair ！”);
break;
default: // amount to if Of the statement else
Console.WriteLine(“ What you entered {0} It makes no sense ”,i);
break;
}
Console.ReadKey();
}
}
}

Be careful :C# Medium switch Statement must be written break, No writing , But there is one case except , Amalgamated case situation , Don't write break.( For example 3)：

Switch The third structure of ： Amalgamated case situation , To omit break.

switch(i)

case 1:

case2:

//

break;

example 3：

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namespace Switch
{
class Program
{
static void Main(string[] args)
{
int i = 200;
switch(i)
{
case 2: // amount to if(if==2)
Console.WriteLine(“ You really are 2！”);
Console.WriteLine(“ You are so talented ！”);
break; //C# You have to write break
case 4:
Console.WriteLine(“ Go to hell. ！”);
break;
case 8:
Console.WriteLine(“ Hair. Hair ！”);
break;
/*
case 100:
Console.WriteLine(“ What you input is the whole money ！”);
Console.WriteLine(“ You are rich ”);
break;
case 200:
Console.WriteLine(“ What you input is the whole money ！”);
Console.WriteLine(“ You are rich ”);
break;
*/

            // The code above is equivalent to the code below   
            case 100:  
            case 200:      // amount to if(i=100||i=200), The only one case No need to break The situation of   
                Console.WriteLine(" What you input is the whole money ！");  
                Console.WriteLine(" You are rich ");  
                break;  


            default:       // amount to if Of the statement else  
                Console.WriteLine(" What you entered {0} It makes no sense ",i);  
                break;  
        }  
        Console.ReadKey();  
    }  
}  

}

Be careful ：switch In the sentence case The value of can only be 2,4,“aaa” Constant , It can't be a variable 、 expression . （ For example 4）

example 4

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namespace Switch
{
class Program
{
static void Main(string[] args)
{
string s1 = Console.ReadLine();
int i = Convert.ToInt32(s1);
int k = 10;
switch(k)
{
case i: // error ：case The median can only be used 2,4,“aaa” Constant , You can't write variables
Console.WriteLine(“ What you input is the same as what the program assumes ！”);
break; //C# You have to write break
}
Console.ReadKey();
}
}
}

summary ：switch Statement and if The difference between sentences ：

●  Greater than or equal to （>=）、 Less than or equal to （<=） For judgment if sentence , And equal to （=） For judgment switch sentence .

● switch Statement case Be similar to if…else…else if…else, But the judgment of discrete value .

   （ The judgment of discrete value is considered to be equal to the judgment of the situation ）.


● switch Generally, it can be used if rewrite , however if Not necessarily switch rewrite （ For example 2）.


●  Don't forget to break.C# in break It's impossible not to write , Except for the merger case The situation of （ For example 3）.

● case  The value in must be a constant , It can't be a variable 、 expression （ For example 4）.