Question

我遇到了do while循环的问题。当我这样做。

它说：使用未分配的变量＆＃34;再次＆＃34;。我完全不知道为什么。

也许是愚蠢的问题......我只是开始学习如何编码我没有编程逻辑＆gt;＆lt ;.干杯

    static void Main(string[] args) {

        double WeightKg = 0.0, HeightCm = 0.0, Weightlbs = 0.0, WeightOz = 0.0, BMI = 0.0, Feet = 0.0, Inches = 0.0;
        int BMIOption;
        string again;

     do{
        string BMIMenu = ("Which Measurement You Want to use to enter the weight and height?"
                        + "\n1)Enter 1 for Metric"
                        + "\n2)Enter 2 for British Imperial:");
        Console.Write(BMIMenu);
        BMIOption = int.Parse(Console.ReadLine());

        if (BMIOption == 1) {
            Console.Write("\nPlease Enter your Weight in Kilogram (kg):");
            WeightKg = double.Parse(Console.ReadLine());
            Console.Write("\nPlease Enter your Height in in centimetres (cm):");
            HeightCm = double.Parse(Console.ReadLine());
            BMI = WeightKg / (HeightCm / 100 * HeightCm / 100);

            if (BMI >= 35.0) {
                Console.WriteLine("\nYour BMI is {0:G},Severe Obesity", BMI);
            } else if (BMI >= 30.0) {
                Console.WriteLine("\nYour BMI is {0:G},Obese", BMI);
            } else if (BMI >= 25.0) {
                Console.WriteLine("\nYour BMI is {0:G},OverWeight", BMI);
            } else if (BMI >= 18.5) {
                Console.WriteLine("\nYour BMI is {0:G},Healthy BodyWeight", BMI);
            } else if (BMI <= 18.5) {
                Console.WriteLine("\nYour BMI is {0:G},UnderWeight", BMI);
            }//End if
            Console.Write("\nWould you like to make an another conversion? \n\n(Enter Y to make an another conversion/Enter any other key to exit):");
            again = Console.ReadLine();

            } else if (BMIOption == 2) {
            Console.WriteLine("Please Enter your Weight in Pounds (lbs):");
            Weightlbs = double.Parse(Console.ReadLine());
            Console.WriteLine("Please Enter your Weight in Ounces (oz):");
            WeightOz = double.Parse(Console.ReadLine());
            Console.WriteLine("Please Enter your Height in Feet (ft):");
            Feet = double.Parse(Console.ReadLine());
            Console.WriteLine("Please Enter your Height in Inches (ins):");
            Inches = double.Parse(Console.ReadLine());

            WeightKg = ((Weightlbs * 16) + WeightOz) / 35.2;
            HeightCm = ((Feet * 12) + Inches) * 2.54;
            BMI = WeightKg / (HeightCm / 100 * HeightCm / 100);

            if (BMI >= 35) {
                Console.WriteLine("Your BMI is {0:G},Severe Obesity", BMI);
            } else if (BMI >= 30) {
                Console.WriteLine("Your BMI is {0:G},Obese", BMI);
            } else if (BMI >= 25) {
                Console.WriteLine("Your BMI is {0:G},OverWeight", BMI);
            } else if (BMI >= 18.5) {
                Console.WriteLine("Your BMI is {0:G},Healthy BodyWeight", BMI);
            } else if (BMI <= 18.5) {
                Console.WriteLine("Your BMI is {0:G},UnderWeight", BMI);
            }//End if
            Console.Write("\nWould you like to make an another conversion? \n\n(Enter Y to make an another conversion/Enter any other key to exit):");
            again = Console.ReadLine();
           }
     } while (again == "y" || again == "Y");
    }
}

}

Answer 1

如果你只专注于代码的重要部分，你就会得到：

string again;
do {
  ...
  if (BMIOption == 1) {
    ...
    again = Console.ReadLine();
  } else if (BMIOption == 2) {
    ...
    again = Console.ReadLine();
  }
} while (again == "y" || again == "Y");

如您所见，BMIOption与1或2不同，则again将不会被初始化。您最有可能将语句移动到ifs以外的地方，如下所示：

do {
  ...
  if (BMIOption == 1) {
    ...
  } else if (BMIOption == 2) {
    ...
  }
  again = Console.ReadLine();
} while (again == "y" || again == "Y");

您还可以使用其他人建议的值初始化again变量，但如果again与1或2不同，则BMIOption不会更新。

Answer 2

编译器错误来自于您声明一个名为again的变量这一事实，但您在使用之前并未（始终）为其分配值。

如果您没有输入分配给它的again块之一，您需要决定if应该具有的值。

您可能希望在声明它时将其初始化为null：

string again = null;

Answer 3

您的string again未分配，并且您不能认为在do-while循环中检查它时将始终具有值。只需将其初始化为任何值，例如string again="";

Answer 4

if (BMIOption == 1) {

将再次设定。但如果是！=并且是！= 2那么再也没有设置。在你再次设置的地方添加if语句，或者声明变量并赋值

string again = string.Empty;

C＃控制台应用程序执行while循环

4 个答案: