C＃错误CS0103：名称“ i”在当前上下文中不存在

Question

Can someone give me some insight on my code. My C# program is suppose to transmit a message from a client to a server but extract and print only the vowels. But it states that my 'i' doesn't exist please help.

// 5. Display the received message:
            Console.WriteLine("[Server] Message of client recieved");
            for (int i = 0; i < totalBytes; i++)
            {
                aChar = Convert.ToChar(incomingDataBuffer[i]);
                Console.Write(aChar);
            }

            {
               aChar = Convert.ToChar(incomingDataBuffer[i]);
               if(aChar == 'a' || aChar == 'A' || aChar == 'e' || aChar == 'E' || aChar == 'i' || aChar == 'I' || aChar == 'o' || aChar == 'O' || aChar == 'u' || aChar == 'U')
               {  
                   Console.Write(aChar);
               }

}

Answer 1

You closed the for loop with the first }. The scope of 'i' is limited to the for { ... } body, so the lower Convert.ToChar is out of the scope of the 'i', it no longer exists.

for (int i = 0; i < totalBytes; i++)
{
  aChar = Convert.ToChar(incomingDataBuffer[i]);
  Console.Write(aChar);
  aChar = Convert.ToChar(incomingDataBuffer[i]);
  if(aChar == 'a' || aChar == 'A' || aChar == 'e' || aChar == 'E' || aChar == 'i' || aChar == 'I' || aChar == 'o' || aChar == 'O' || aChar == 'u' || aChar == 'U')
  {  
    Console.Write(aChar);
  }
}

Would fix it, or you could create two for loops to get the output to be what you want it to be.

Answer 2

您只能在for循环内使用“ i”，因为它是局部变量。

Answer 3

Seems like you meant to include the second part of your code in the for loop, so just need to ensure the closing curly brace is after the second part.

But you can write your code in a simpler way

 var s = Encoding.ASCII.GetString(incomingDataBuffer);
 Console.WriteLine(s);
 Console.WriteLine(string.Join("",s.Where(c => "aeiou".Contains(char.ToLower(c)))));