C#中如何转移goto语句的控制权
How to transfer the control of goto statement in C#
我是编程初学者，我正在尝试这个获取用户名并对其进行排序等的简单程序。
class Program
{
static void Main(string[] args)
{
int number;
dynamic y;
string[] answer = new string[10];
cases:
Console.WriteLine("Enter the options given below 1.Add students\n 2.View all details\n 3.Sorting\n 4.Exit\n");
int input = Convert.ToInt16(Console.ReadLine());
switch (input)
{
case 1:
Console.WriteLine("Enter the Number of Students to be added to the List");
number = Convert.ToInt16(Console.ReadLine());
for (int i = 0; i < number; i++)
{
answer[i] = Console.ReadLine();
}
case 2:
foreach (var item in answer)
{
Console.WriteLine(item.ToString());
}
break;
case 3:
Array.Sort(answer);
foreach (var item in answer)
{
Console.WriteLine(item.ToString());
}
break;
case 4:
Console.WriteLine("Are you sure you want to exit");
Console.WriteLine("1 for Yes and N for No");
y = (char)Console.Read();
if ((y == 1))
{
goto cases;
}
else
{
goto thankyou;
}
thankyou:
Console.WriteLine("thank you");
break;
}
Console.WriteLine("Are you sure you want to exit");
Console.WriteLine("Y for Yes and 1 for No");
y = (char)Console.Read();
if ((y == 1))
{
goto cases;
}
else
{
goto thankyou;
}
}
}
我的问题是每次操作后我都会询问它是否应该继续。我已经添加了 go-to 语句，但是当按下否时，它显示了我声明的 input 变量的异常。
我可以使用 go-to 方法吗？有什么方法可以做到这一点吗？
这里有什么问题吗？
如果你想在你的程序中使用循环，你应该使用 C# 中的循环结构之一。在这种情况下，while 循环会起作用：
bool keepPrompting = true;
while(keepPrompting) {
Console.WriteLine("Enter the options given below 1.Add students\n 2.View all details\n 3.Sorting\n 4.Exit\n");
int input = Convert.ToInt16(Console.ReadLine());
// The case statement on input goes here
Console.WriteLine("Are you sure you want to exit");
Console.WriteLine("Y for Yes and 1 for No");
var y = (char)Console.Read();
if (y != 'y')
keepPrompting = false;
}
Console.WriteLine("thank you");
goto 几乎从未在 C#（或任何其他语言）中使用过，因为很难遵循一个可以跳转到几乎任何位置的程序，而循环具有定义的流程。
你不应该用 goto 这样做。您应该始终完全避免使用 goto。如果您出于某种原因认为需要使用 goto，您应该找到一种不用 goto 的方法。这是一个如何在避免 goto.
的情况下执行此操作的示例
class Program
{
static void Main(string[] args)
{
int number;
dynamic y;
string[] answer = new string[10];
bool result = false;
while(!result) {
Console.WriteLine("Enter the options given below 1.Add students\n 2.View all details\n 3.Sorting\n 4.Exit\n");
int input = Convert.ToInt16(Console.ReadLine());
switch (input)
{
case 1:
Console.WriteLine("Enter the Number of Students to be added to the List");
number = Convert.ToInt16(Console.ReadLine());
for (int i = 0; i < number; i++)
{
answer[i] = Console.ReadLine();
}
break;
case 2:
foreach (var item in answer)
{
Console.WriteLine(item.ToString());
}
break;
case 3:
Array.Sort(answer);
foreach (var item in answer)
{
Console.WriteLine(item.ToString());
}
break;
case 4:
Console.WriteLine("Are you sure you want to exit");
Console.WriteLine("1 for Yes and N for No");
result = ((char)Console.Read()) == 'y';
break;
}
}
Console.WriteLine("thank you");
}
}
}
static void Main(string[] args)
{
// First you need a few loops, avoid goto's at all costs they make code much harder to read
// There are better ways to do this but this will get it done
// List<string> answer = new List<string>(); would be better here because it resizes automatically when adding
// I left it like this because it looks like a school project
string[] answer = new string[0]; // create variable before loops so it is not recreated on each iteration
bool exit = false; // create bool variable and use it to exit infinite loop by setting it to true when user chooses option 4
for (;;) // create outer infinit loop to so the code will execute until you want you break; when option 4 is entered
{
int option;
for (;;)// create infinite loop to get user input for which option they want
{
Console.Clear();
Console.WriteLine("Enter the options given below\n1.Add students\n2.View all details\n3.Sorting\n4.Exit\n");
if (int.TryParse(Console.ReadLine(), out option) && option >= 1 && option <= 4)
{ break; /*user entered valid option so we break from this infinit loop*/ }
else
{ Console.Clear(); /*User did not enter a valid option so clear the console window*/ }
}
switch (option) // switch cases to handle each of the possible options entered
{
case 1:
// user chose option 1
int number = 0;
while (number <= 0)
{
Console.Clear();
Console.WriteLine("Enter the number of students to add.");
int.TryParse(Console.ReadLine(), out number);
answer = new string[number]; // re-initize number of students to add
for(int i=0;i<number;i++)
{
Console.Clear();
Console.WriteLine("Enter Name: ");
answer[i] = Console.ReadLine();
}
}
break; // break out of case 1
case 2:
// user chose option 2
break;// break out of case 2
case 3:
// user chose option 3
if (answer.Length > 0)
{
Console.Clear();
Console.WriteLine("Sorted student names:");
Array.Sort(answer);
Console.WriteLine(string.Join("\n", answer));
Console.ReadLine(); // pause screen for reading
}
break;// break out of case 3
case 4:
// user chose option 4
while (true) // loop until a Y or 1 is entered
{
Console.WriteLine("Are you sure you want to exit\nY for YES and 1 for NO");
char y = (char)Console.Read();
if (y == 'Y' || y == 'y')
{ exit = true; break; /*user is sure they want to exit*/ }
else if (y == '1')
{ Console.Clear(); break; /*user decided not to exit*/ }
else
{ Console.Clear(); }
}
break; // break out of case 4
}
if (exit) break; // if exit variable true then break out of outer infinite loop
}
}
static void Main(string[] args)
{
// First you need a few loops, avoid goto's at all costs they make code much harder to read
// There are better ways to do this but this will get it done
// List<string> answer = new List<string>(); would be better here because it resizes automatically when adding
// I left it like this because it looks like a school project
List<string> answer = new List<string>(); // create variable before loops so it is not recreated on each iteration
bool exit = false; // create bool variable and use it to exit infinite loop by setting it to true when user chooses option 4
for (;;) // create outer infinit loop to so the code will execute until you want you break; when option 4 is entered
{
int option;
for (;;)// create infinite loop to get user input for which option they want
{
Console.Clear();
Console.WriteLine("Enter the options given below\n1.Add students\n2.View all details\n3.Sorting\n4.Exit\n");
if (int.TryParse(Console.ReadLine(), out option) && option >= 1 && option <= 4)
{ break; /*user entered valid option so we break from this infinit loop*/ }
else
{ Console.Clear(); /*User did not enter a valid option so clear the console window*/ }
}
switch (option) // switch cases to handle each of the possible options entered
{
case 1:
// user chose option 1
int number = 0;
while (number <= 0)
{
Console.Clear();
Console.WriteLine("Enter the number of students to add.");
int.TryParse(Console.ReadLine(), out number);
// Because "answer" is now a list it does not have to be sized
for(int i=0;i<number;i++)
{
Console.Clear();
Console.WriteLine("Enter Name: ");
// with a list, the previous list of students are not wiped out
// we also don't have to be carefull about writing outside array bounds because of the add method
answer.Add(Console.ReadLine());
}
}
break; // break out of case 1
case 2:
// user chose option 2
break;// break out of case 2
case 3:
// user chose option 3
if (answer.Count > 0)
{
Console.Clear();
Console.WriteLine("Sorted student names:");
answer.Sort(); // List<string> have a Sort member method
Console.WriteLine(string.Join("\n", answer));
}
else
{ Console.WriteLine("No students exist to sort or list."); }
Console.ReadLine(); // pause screen for reading
break;// break out of case 3
case 4:
// user chose option 4
while (true) // loop until a Y or 1 is entered
{
Console.WriteLine("Are you sure you want to exit\nY for YES and 1 for NO");
char y = (char)Console.Read();
if (y == 'Y' || y == 'y')
{ exit = true; break; /*user is sure they want to exit*/ }
else if (y == '1')
{ Console.Clear(); break; /*user decided not to exit*/ }
else
{ Console.Clear(); }
}
break; // break out of case 4
}
if (exit) break; // if exit variable true then break out of outer infinite loop
}
}
我是编程初学者，我正在尝试这个获取用户名并对其进行排序等的简单程序。
class Program
{
static void Main(string[] args)
{
int number;
dynamic y;
string[] answer = new string[10];
cases:
Console.WriteLine("Enter the options given below 1.Add students\n 2.View all details\n 3.Sorting\n 4.Exit\n");
int input = Convert.ToInt16(Console.ReadLine());
switch (input)
{
case 1:
Console.WriteLine("Enter the Number of Students to be added to the List");
number = Convert.ToInt16(Console.ReadLine());
for (int i = 0; i < number; i++)
{
answer[i] = Console.ReadLine();
}
case 2:
foreach (var item in answer)
{
Console.WriteLine(item.ToString());
}
break;
case 3:
Array.Sort(answer);
foreach (var item in answer)
{
Console.WriteLine(item.ToString());
}
break;
case 4:
Console.WriteLine("Are you sure you want to exit");
Console.WriteLine("1 for Yes and N for No");
y = (char)Console.Read();
if ((y == 1))
{
goto cases;
}
else
{
goto thankyou;
}
thankyou:
Console.WriteLine("thank you");
break;
}
Console.WriteLine("Are you sure you want to exit");
Console.WriteLine("Y for Yes and 1 for No");
y = (char)Console.Read();
if ((y == 1))
{
goto cases;
}
else
{
goto thankyou;
}
}
}
我的问题是每次操作后我都会询问它是否应该继续。我已经添加了 go-to 语句，但是当按下否时，它显示了我声明的 input 变量的异常。
我可以使用 go-to 方法吗？有什么方法可以做到这一点吗？
如果你想在你的程序中使用循环，你应该使用 C# 中的循环结构之一。在这种情况下，while 循环会起作用：
bool keepPrompting = true;
while(keepPrompting) {
Console.WriteLine("Enter the options given below 1.Add students\n 2.View all details\n 3.Sorting\n 4.Exit\n");
int input = Convert.ToInt16(Console.ReadLine());
// The case statement on input goes here
Console.WriteLine("Are you sure you want to exit");
Console.WriteLine("Y for Yes and 1 for No");
var y = (char)Console.Read();
if (y != 'y')
keepPrompting = false;
}
Console.WriteLine("thank you");
goto 几乎从未在 C#（或任何其他语言）中使用过，因为很难遵循一个可以跳转到几乎任何位置的程序，而循环具有定义的流程。
你不应该用 goto 这样做。您应该始终完全避免使用 goto。如果您出于某种原因认为需要使用 goto，您应该找到一种不用 goto 的方法。这是一个如何在避免 goto.
class Program
{
static void Main(string[] args)
{
int number;
dynamic y;
string[] answer = new string[10];
bool result = false;
while(!result) {
Console.WriteLine("Enter the options given below 1.Add students\n 2.View all details\n 3.Sorting\n 4.Exit\n");
int input = Convert.ToInt16(Console.ReadLine());
switch (input)
{
case 1:
Console.WriteLine("Enter the Number of Students to be added to the List");
number = Convert.ToInt16(Console.ReadLine());
for (int i = 0; i < number; i++)
{
answer[i] = Console.ReadLine();
}
break;
case 2:
foreach (var item in answer)
{
Console.WriteLine(item.ToString());
}
break;
case 3:
Array.Sort(answer);
foreach (var item in answer)
{
Console.WriteLine(item.ToString());
}
break;
case 4:
Console.WriteLine("Are you sure you want to exit");
Console.WriteLine("1 for Yes and N for No");
result = ((char)Console.Read()) == 'y';
break;
}
}
Console.WriteLine("thank you");
}
}
}
static void Main(string[] args)
{
// First you need a few loops, avoid goto's at all costs they make code much harder to read
// There are better ways to do this but this will get it done
// List<string> answer = new List<string>(); would be better here because it resizes automatically when adding
// I left it like this because it looks like a school project
string[] answer = new string[0]; // create variable before loops so it is not recreated on each iteration
bool exit = false; // create bool variable and use it to exit infinite loop by setting it to true when user chooses option 4
for (;;) // create outer infinit loop to so the code will execute until you want you break; when option 4 is entered
{
int option;
for (;;)// create infinite loop to get user input for which option they want
{
Console.Clear();
Console.WriteLine("Enter the options given below\n1.Add students\n2.View all details\n3.Sorting\n4.Exit\n");
if (int.TryParse(Console.ReadLine(), out option) && option >= 1 && option <= 4)
{ break; /*user entered valid option so we break from this infinit loop*/ }
else
{ Console.Clear(); /*User did not enter a valid option so clear the console window*/ }
}
switch (option) // switch cases to handle each of the possible options entered
{
case 1:
// user chose option 1
int number = 0;
while (number <= 0)
{
Console.Clear();
Console.WriteLine("Enter the number of students to add.");
int.TryParse(Console.ReadLine(), out number);
answer = new string[number]; // re-initize number of students to add
for(int i=0;i<number;i++)
{
Console.Clear();
Console.WriteLine("Enter Name: ");
answer[i] = Console.ReadLine();
}
}
break; // break out of case 1
case 2:
// user chose option 2
break;// break out of case 2
case 3:
// user chose option 3
if (answer.Length > 0)
{
Console.Clear();
Console.WriteLine("Sorted student names:");
Array.Sort(answer);
Console.WriteLine(string.Join("\n", answer));
Console.ReadLine(); // pause screen for reading
}
break;// break out of case 3
case 4:
// user chose option 4
while (true) // loop until a Y or 1 is entered
{
Console.WriteLine("Are you sure you want to exit\nY for YES and 1 for NO");
char y = (char)Console.Read();
if (y == 'Y' || y == 'y')
{ exit = true; break; /*user is sure they want to exit*/ }
else if (y == '1')
{ Console.Clear(); break; /*user decided not to exit*/ }
else
{ Console.Clear(); }
}
break; // break out of case 4
}
if (exit) break; // if exit variable true then break out of outer infinite loop
}
}
static void Main(string[] args)
{
// First you need a few loops, avoid goto's at all costs they make code much harder to read
// There are better ways to do this but this will get it done
// List<string> answer = new List<string>(); would be better here because it resizes automatically when adding
// I left it like this because it looks like a school project
List<string> answer = new List<string>(); // create variable before loops so it is not recreated on each iteration
bool exit = false; // create bool variable and use it to exit infinite loop by setting it to true when user chooses option 4
for (;;) // create outer infinit loop to so the code will execute until you want you break; when option 4 is entered
{
int option;
for (;;)// create infinite loop to get user input for which option they want
{
Console.Clear();
Console.WriteLine("Enter the options given below\n1.Add students\n2.View all details\n3.Sorting\n4.Exit\n");
if (int.TryParse(Console.ReadLine(), out option) && option >= 1 && option <= 4)
{ break; /*user entered valid option so we break from this infinit loop*/ }
else
{ Console.Clear(); /*User did not enter a valid option so clear the console window*/ }
}
switch (option) // switch cases to handle each of the possible options entered
{
case 1:
// user chose option 1
int number = 0;
while (number <= 0)
{
Console.Clear();
Console.WriteLine("Enter the number of students to add.");
int.TryParse(Console.ReadLine(), out number);
// Because "answer" is now a list it does not have to be sized
for(int i=0;i<number;i++)
{
Console.Clear();
Console.WriteLine("Enter Name: ");
// with a list, the previous list of students are not wiped out
// we also don't have to be carefull about writing outside array bounds because of the add method
answer.Add(Console.ReadLine());
}
}
break; // break out of case 1
case 2:
// user chose option 2
break;// break out of case 2
case 3:
// user chose option 3
if (answer.Count > 0)
{
Console.Clear();
Console.WriteLine("Sorted student names:");
answer.Sort(); // List<string> have a Sort member method
Console.WriteLine(string.Join("\n", answer));
}
else
{ Console.WriteLine("No students exist to sort or list."); }
Console.ReadLine(); // pause screen for reading
break;// break out of case 3
case 4:
// user chose option 4
while (true) // loop until a Y or 1 is entered
{
Console.WriteLine("Are you sure you want to exit\nY for YES and 1 for NO");
char y = (char)Console.Read();
if (y == 'Y' || y == 'y')
{ exit = true; break; /*user is sure they want to exit*/ }
else if (y == '1')
{ Console.Clear(); break; /*user decided not to exit*/ }
else
{ Console.Clear(); }
}
break; // break out of case 4
}
if (exit) break; // if exit variable true then break out of outer infinite loop
}
}