C# 并非所有代码路径都返回值

我有一个很大的问题。我的CreateArmy方法不断返回错误：并非所有代码路径都返回值。我肯定它们都返回一个值：

public string CreateArmy(string inputFile)
{
   string grabFile = inputFile + ".txt";
   int counter = 0;
   string line;
   try
   {
      // Read the file and display it line by line.
      StreamReader file = new StreamReader(grabFile);

      while ((line = file.ReadLine()) != null)
      {
         char[] fixedCommands = line.Remove(0, 3).ToCharArray();
         commands[0] = fixedCommands[0];
         commands[1] = fixedCommands[1];
         commands[2] = fixedCommands[2];
         byte[] newline = Encoding.ASCII.GetBytes(Environment.NewLine);
         commands[].Write(newline, 0, newline.Length);
         counter++;
      }
      char[] newcommands = new string(commands).Remove(0, 3).ToCharArray();

      file.Close();
      MessageBox.Show("There are " + counter + " robots!");
   }
   catch (Exception e)
   {
      MessageBox.Show("Please tell me the .txt file type. Do not include the .txt extension.");
      MessageBox.Show(e.Message);
   }
}

---

您的方法应该返回一个字符串

public string CreateArmy(string inputFile)

然而，现在在您的方法中有一个这样做的return语句

如果不需要return语句，则使方法无效，即不返回：

public void CreateArmy(string inputFile)

否则，请确保从所有可能的代码路径返回正确的数据。

不要将CreateArmy函数设置为返回字符串，或者在代码中添加return语句

解决方案1：

public void CreateArmy(string inputFile)
        {
        string grabFile = inputFile + ".txt";
        int counter = 0;
        string line;
        try
        {
            // Read the file and display it line by line.
            StreamReader file = new StreamReader(grabFile);

        while ((line = file.ReadLine()) != null)
        {
            char[] fixedCommands = line.Remove(0, 3).ToCharArray();
            commands[0] = fixedCommands[0];
            commands[1] = fixedCommands[1];
            commands[2] = fixedCommands[2];
            byte[] newline = Encoding.ASCII.GetBytes(Environment.NewLine);
            commands[].Write(newline, 0, newline.Length);
            counter++;
        }

        char[] newcommands = new string(commands).Remove(0, 3).ToCharArray();

        file.Close();

        MessageBox.Show("There are " + counter + " robots!");
    }
    catch (Exception e)
    {
        MessageBox.Show("Please tell me the .txt file type. Do not include the .txt extension.");
        MessageBox.Show(e.Message);
    }
}

解决方案2：

public string CreateArmy(string inputFile)
        {
        string grabFile = inputFile + ".txt";
        int counter = 0;
        string line;
        try
        {
            // Read the file and display it line by line.
            StreamReader file = new StreamReader(grabFile);

        while ((line = file.ReadLine()) != null)
        {
            char[] fixedCommands = line.Remove(0, 3).ToCharArray();
            commands[0] = fixedCommands[0];
            commands[1] = fixedCommands[1];
            commands[2] = fixedCommands[2];
            byte[] newline = Encoding.ASCII.GetBytes(Environment.NewLine);
            commands[].Write(newline, 0, newline.Length);
            counter++;
        }

        char[] newcommands = new string(commands).Remove(0, 3).ToCharArray();

        file.Close();

        MessageBox.Show("There are " + counter + " robots!");

        return null;  // OR return some other string value!
    }
    catch (Exception e)
    {
        MessageBox.Show("Please tell me the .txt file type. Do not include the .txt extension.");
        MessageBox.Show(e.Message);
    }
}

---

您需要一个return语句来在Try块中以及Catch块中返回字符串，以防抛出异常

---

如果您不想从方法调用返回任何内容，请将方法的返回类型设置为void。

您已声明该方法将返回字符串，但它不会。您没有一个返回语句。显示messagebox与返回字符串不同。代码中没有return语句…因此它不会返回任何内容。臭名昭著的返回会使您处于空白中…或…永远不会返回的空白。。。