C# 错误；4 ；无效的表达式项'；其他'；_C#_Syntax Error

C# 错误；4 ；无效的表达式项'；其他'；

C# 错误；4 ；无效的表达式项'；其他'；,c#,syntax-error,C#,Syntax Error,我见过其他问题，但我是c的初学者# 代码：您不应该在else后面加分号，并且在else前面缺少一个结束符 namespace Input_Program { class Program { static void Main() { char Y = Console.ReadKey().KeyChar; Console.WriteLine("Welcome to my bool program!");

我见过其他问题，但我是c的初学者#

代码：

您不应该在else后面加分号，并且在else前面缺少一个结束符

namespace Input_Program
{
    class Program
    {
        static void Main()
        {
            char Y = Console.ReadKey().KeyChar;
            Console.WriteLine("Welcome to my bool program!");
            Console.WriteLine("Input a NON capital y or n when told to.");
            if(Y == 'y')
            {
                Console.WriteLine("Thank you,Please wait.....");
                Console.WriteLine("You input Y");
            }
            else
            {
                if(Y == 'n')
                {
                    Console.WriteLine("You input N");
                }
            }
            Console.ReadLine();
        }
    }
}

您不应该在else后面加分号，并且在else前面缺少一个结束符

namespace Input_Program
{
    class Program
    {
        static void Main()
        {
            char Y = Console.ReadKey().KeyChar;
            Console.WriteLine("Welcome to my bool program!");
            Console.WriteLine("Input a NON capital y or n when told to.");
            if(Y == 'y')
            {
                Console.WriteLine("Thank you,Please wait.....");
                Console.WriteLine("You input Y");
            }
            else
            {
                if(Y == 'n')
                {
                    Console.WriteLine("You input N");
                }
            }
            Console.ReadLine();
        }
    }
}

在由

if

控制的两条语句之后（就在

else

之前），需要一个右大括号

。此外，完成此操作后，请删除

else

后面的分号。

在由

if

控制的两个语句之后（就在

else

之前），需要一个右括号

。此外，完成此操作后，请删除

else

后面的分号

{
    char Y = Console.ReadKey().KeyChar;
    Console.WriteLine("Welcome to my bool program!")
    Console.WriteLine("Input a NON capital y or n when told to.");

    if(Y == 'y')
    {
        Console.WriteLine("Thank you,Please wait.....");
        Console.WriteLine("You input Y");    
    }else
    {
        if(Y == 'n')
        {
            Console.WriteLine("You input N");
        }
    }

    Console.ReadLine();
}

匹配缩进可以帮助您看到需要/不需要闭合的花括号，并且不需要在else后面加分号

namespace Input_Program
{
    class Program
    {
        static void Main()
        {
            char Y = Console.ReadKey().KeyChar;
            Console.WriteLine("Welcome to my bool program!");
            Console.WriteLine("Input a NON capital y or n when told to.");
            if(Y == 'y')
            {
                Console.WriteLine("Thank you,Please wait.....");
                Console.WriteLine("You input Y");
            }
            else
            {
                if(Y == 'n')
                {
                    Console.WriteLine("You input N");
                }
            }
            Console.ReadLine();
        }
    }
}

您还可以将结构更改为if/else，或两个if，以获得相同的结果

{
    char Y = Console.ReadKey().KeyChar;
    Console.WriteLine("Welcome to my bool program!")
    Console.WriteLine("Input a NON capital y or n when told to.");

    if(Y == 'y')
    {
        Console.WriteLine("Thank you,Please wait.....");
        Console.WriteLine("You input Y");    
    }

    if(Y == 'n')
    {
        Console.WriteLine("You input N");
    }

    Console.ReadLine();
}

匹配缩进可以帮助您看到需要/不需要闭合的花括号，并且不需要在else后面加分号

namespace Input_Program
{
    class Program
    {
        static void Main()
        {
            char Y = Console.ReadKey().KeyChar;
            Console.WriteLine("Welcome to my bool program!");
            Console.WriteLine("Input a NON capital y or n when told to.");
            if(Y == 'y')
            {
                Console.WriteLine("Thank you,Please wait.....");
                Console.WriteLine("You input Y");
            }
            else
            {
                if(Y == 'n')
                {
                    Console.WriteLine("You input N");
                }
            }
            Console.ReadLine();
        }
    }
}

您还可以将结构更改为if/else，或两个if，以获得相同的结果

{
    char Y = Console.ReadKey().KeyChar;
    Console.WriteLine("Welcome to my bool program!")
    Console.WriteLine("Input a NON capital y or n when told to.");

    if(Y == 'y')
    {
        Console.WriteLine("Thank you,Please wait.....");
        Console.WriteLine("You input Y");    
    }

    if(Y == 'n')
    {
        Console.WriteLine("You input N");
    }

    Console.ReadLine();
}

else

后面没有分号，您需要合上大括号。重做语法：

if(Y == 'y'){
 Console.WriteLine("Thank you,Please wait.....");
 Console.WriteLine("You input Y");
}
else{
 if(Y == 'n'){
  Console.WriteLine("You input N");  
 }      
}

编辑：

else{if（Y=='n'）{…}

最好重构为

else，如果（Y=='n'）{…}

else

后面没有分号，您需要关闭大括号。重做语法：

if(Y == 'y'){
 Console.WriteLine("Thank you,Please wait.....");
 Console.WriteLine("You input Y");
}
else{
 if(Y == 'n'){
  Console.WriteLine("You input N");  
 }      
}

编辑：

else{if（Y='n'）{…}

重构为

else如果（Y='n'）{…}

我注意到两件事

if(Y == 'y')
        {
            Console.WriteLine("Thank you,Please wait.....");
            Console.WriteLine("You input Y");
            // you need to close the if with a } on this line     
            else; //no semicolon after else
            {
                if(Y == 'n')
                {
                    Console.WriteLine("You input N");
                }
             }
        }

我注意到两件事

if(Y == 'y')
        {
            Console.WriteLine("Thank you,Please wait.....");
            Console.WriteLine("You input Y");
            // you need to close the if with a } on this line     
            else; //no semicolon after else
            {
                if(Y == 'n')
                {
                    Console.WriteLine("You input N");
                }
             }
        }

任何使用大括号的东西都是“代码块”。定义

类

时，在花括号内定义一块代码，如下所示：

public class MyClass
{

}

大括号内的内容被视为“在该范围内”。例如：

public class MyClass
{
    // This method is in the scope of MyClass
    public void MyMethod()
    {
        // This variable is in the scope of MyMethod.
        // It is only accessible from within this method because that is where
        // it is defined.
        string myString = "Hello Method.";
    }

    // This variable is in the scope of MyClass.
    // It is accessible within MyClass, including all methods that are also in scope
    // of MyClass
    public string myGlobalString = "Hello Global.";
}

public class MyClass
{
    public void MyMethod(string myString)
    {
        if (myString == "Hello")
        {
            // Read like English. "If variable myString equals the value 'Hello', then do this code within this block."
        }
        else if (myString == "Goodbye")
        {
            // "...or else if variable myString equals the value 'Goodbye', then do this code within this block instead.
        }
        else if (myString == "Good Morning")
        {
            // "...or else if variable myString equals the value 'Good Morning', then do this code within this block instead.
        }
        else
        {
            // "...or else do this code if variable myString does not match any of the above code statements.
        }

        // You are not required to include "else" or even "else if". You could just do a single IF statement like this:
        if (myString == "hi)
        {
            // "If variable myString equals the value 'hi' then do this, otherwise do nothing."
        }
    }
}

对于

IF

语句，它们是一系列块语句，只能包含在方法范围内（例如，在类中不能使用

IF

语句）。代码只能在语句提供的给定路径中的一条路径上运行。例如：

public class MyClass
{
    // This method is in the scope of MyClass
    public void MyMethod()
    {
        // This variable is in the scope of MyMethod.
        // It is only accessible from within this method because that is where
        // it is defined.
        string myString = "Hello Method.";
    }

    // This variable is in the scope of MyClass.
    // It is accessible within MyClass, including all methods that are also in scope
    // of MyClass
    public string myGlobalString = "Hello Global.";
}

public class MyClass
{
    public void MyMethod(string myString)
    {
        if (myString == "Hello")
        {
            // Read like English. "If variable myString equals the value 'Hello', then do this code within this block."
        }
        else if (myString == "Goodbye")
        {
            // "...or else if variable myString equals the value 'Goodbye', then do this code within this block instead.
        }
        else if (myString == "Good Morning")
        {
            // "...or else if variable myString equals the value 'Good Morning', then do this code within this block instead.
        }
        else
        {
            // "...or else do this code if variable myString does not match any of the above code statements.
        }

        // You are not required to include "else" or even "else if". You could just do a single IF statement like this:
        if (myString == "hi)
        {
            // "If variable myString equals the value 'hi' then do this, otherwise do nothing."
        }
    }
}

任何使用大括号的东西都是“代码块”。定义

类

时，在花括号内定义一块代码，如下所示：

public class MyClass
{

}

大括号内的内容被视为“在该范围内”。例如：

public class MyClass
{
    // This method is in the scope of MyClass
    public void MyMethod()
    {
        // This variable is in the scope of MyMethod.
        // It is only accessible from within this method because that is where
        // it is defined.
        string myString = "Hello Method.";
    }

    // This variable is in the scope of MyClass.
    // It is accessible within MyClass, including all methods that are also in scope
    // of MyClass
    public string myGlobalString = "Hello Global.";
}

public class MyClass
{
    public void MyMethod(string myString)
    {
        if (myString == "Hello")
        {
            // Read like English. "If variable myString equals the value 'Hello', then do this code within this block."
        }
        else if (myString == "Goodbye")
        {
            // "...or else if variable myString equals the value 'Goodbye', then do this code within this block instead.
        }
        else if (myString == "Good Morning")
        {
            // "...or else if variable myString equals the value 'Good Morning', then do this code within this block instead.
        }
        else
        {
            // "...or else do this code if variable myString does not match any of the above code statements.
        }

        // You are not required to include "else" or even "else if". You could just do a single IF statement like this:
        if (myString == "hi)
        {
            // "If variable myString equals the value 'hi' then do this, otherwise do nothing."
        }
    }
}

对于

IF

语句，它们是一系列块语句，只能包含在方法范围内（例如，在类中不能使用

IF

语句）。代码只能在语句提供的给定路径中的一条路径上运行。例如：

public class MyClass
{
    // This method is in the scope of MyClass
    public void MyMethod()
    {
        // This variable is in the scope of MyMethod.
        // It is only accessible from within this method because that is where
        // it is defined.
        string myString = "Hello Method.";
    }

    // This variable is in the scope of MyClass.
    // It is accessible within MyClass, including all methods that are also in scope
    // of MyClass
    public string myGlobalString = "Hello Global.";
}

public class MyClass
{
    public void MyMethod(string myString)
    {
        if (myString == "Hello")
        {
            // Read like English. "If variable myString equals the value 'Hello', then do this code within this block."
        }
        else if (myString == "Goodbye")
        {
            // "...or else if variable myString equals the value 'Goodbye', then do this code within this block instead.
        }
        else if (myString == "Good Morning")
        {
            // "...or else if variable myString equals the value 'Good Morning', then do this code within this block instead.
        }
        else
        {
            // "...or else do this code if variable myString does not match any of the above code statements.
        }

        // You are not required to include "else" or even "else if". You could just do a single IF statement like this:
        if (myString == "hi)
        {
            // "If variable myString equals the value 'hi' then do this, otherwise do nothing."
        }
    }
}

尝试了分号技巧，但它说它是预期的；在elseJust之后，因为编译器说它期望某些东西，并不意味着正确的答案是将它放在那里。：）您的右括号放错了位置。删除

控制台前面的

命令@Chevex:我删除了违规的}。谢谢尝试了分号技巧，但它说它是预期的；在elseJust之后，因为编译器说它期望某些东西，并不意味着正确的答案是将它放在那里。：）您的右括号放错了位置。删除}
控制台前面的命令@Chevex:我删除了违规的}。谢谢我知道你是个初学者，你正在学习。有一件事，你想嵌入到你的脑海中，那就是保持格式的一致性。每次使用左大括号{
开始一个新块时，应将下面的每一行缩进一个附加级别，并保持所有内容对齐，直到到达匹配的右大括号}
。如果您这样做了，您就可以很容易地看到您的代码存在问题。大括号不匹配，语句不应该出现，等等。Visual Studio甚至可以帮助您进行缩进，只要您遵循它。您可以使用CTRL+K，D自动重新格式化文档。我知道您是初学者，正在学习。有一件事，你想嵌入到你的脑海中，那就是保持格式的一致性。每次使用左大括号{
开始一个新块时，应将下面的每一行缩进一个附加级别，并保持所有内容对齐，直到到达匹配的右大括号}
。如果您这样做了，您就可以很容易地看到您的代码存在问题。大括号不匹配，语句不应该出现在语句中，等等。只要遵循它，Visual Studio甚至可以帮助您进行缩进。您可以使用CTRL+K，D自动重新格式化文档。