所以我试图重新开始编码（以前在大学一年级，打算回去，但是需要重新开始。做这个简单的控制台应用程序并得到这个错误。
使用未分配的局部变量
我尝试在不同部分将卡路里设置为null，0、200等 代码，但似乎无济于事。
static void Main(string[] args)
{
Console.WriteLine("Gender: Male(M)/Female(F)?");
string gender = Console.ReadLine().ToLower();
Console.WriteLine("Age?");
int age = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("Height?");
int height = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("Weight in KG?");
int weightKG = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("How active are you?(Choose by inserting the number)");
Console.WriteLine("1.No exercise");
Console.WriteLine("2.Little to no exercise");
Console.WriteLine("3.Light exercise(1-3 days a week)");
Console.WriteLine("4.Moderate exercise(3-5 days a week");
Console.WriteLine("5.Heavy exercise(6-7days a week)");
Console.WriteLine("6.Very heavy exercise(Twice per day, extra heavy workouts");
int activityLevel = Convert.ToInt32(Console.ReadLine());
if (gender == "m")
{
int calories = Convert.ToInt32(66.4730 + (13.7516 * weightKG) + (5.0033 * height) - (6.7550 * age));
// Console.WriteLine("Your daily calories are: {0}kcal",calories);
}
else if (gender == "f")
{
int calories = Convert.ToInt32(655.0955 + (9.5634 * weightKG) + (1.8496 * height) - (4.6756 * age));
// Console.WriteLine("Your daily calories are: {0} kcal", calories);
}
else
{
Console.WriteLine("Please choose correct gender Male(M) or Female(F).");
}
if (activityLevel == 0)
{
int calories = Convert.ToInt32(calories * 1);
Console.WriteLine("Your daily calories are: {0} kcal", calories);
}
else if (activityLevel == 1)
{
int calories = Convert.ToInt32(calories * 1.2);
Console.WriteLine("Your daily calories are: {0} kcal", calories);
}
else if (activityLevel == 2)
{
int calories = Convert.ToInt32(calories * 1.375);
Console.WriteLine("Your daily calories are: {0} kcal", calories);
}
else if (activityLevel == 3)
{
int calories = Convert.ToInt32(calories * 1.55);
Console.WriteLine("Your daily calories are: {0} kcal", calories);
}
else if (activityLevel == 4)
{
int calories = Convert.ToInt32(calories * 1.725);
Console.WriteLine("Your daily calories are: {0} kcal", calories);
}
else if (activityLevel == 5)
{
int calories = Convert.ToInt32(calories * 1.9);
Console.WriteLine("Your daily calories are: {0} kcal", calories);
}
else
{
Console.WriteLine("Please choose a number between 0 and 5");
}
}
}
}
答案 0 :(得分：0)
您要声明一个变量，然后在计算中使用它。
int calories = Convert.ToInt32(calories * 1);
这实际上与0 * n相同；
该变量应保存一个值，然后将其声明移动到此行下方：
int activityLevel = Convert.ToInt32(Console.ReadLine());
所以... int calories = 0;
static void Main(string[] args)
{
Console.WriteLine("Gender: Male(M)/Female(F)?");
string gender = Console.ReadLine().ToLower();
Console.WriteLine("Age?");
int age = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("Height?");
int height = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("Weight in KG?");
int weightKG = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("How active are you?(Choose by inserting the number)");
Console.WriteLine("1.No exercise");
Console.WriteLine("2.Little to no exercise");
Console.WriteLine("3.Light exercise(1-3 days a week)");
Console.WriteLine("4.Moderate exercise(3-5 days a week");
Console.WriteLine("5.Heavy exercise(6-7days a week)");
Console.WriteLine("6.Very heavy exercise(Twice per day, extra heavy workouts");
int activityLevel = Convert.ToInt32(Console.ReadLine());
int calories = 0;
if (gender == "m")
{
calories = Convert.ToInt32(66.4730 + (13.7516 * weightKG) + (5.0033 * height) - (6.7550 * age));
// Console.WriteLine("Your daily calories are: {0}kcal",calories);
}
else if (gender == "f")
{
calories = Convert.ToInt32(655.0955 + (9.5634 * weightKG) + (1.8496 * height) - (4.6756 * age));
// Console.WriteLine("Your daily calories are: {0} kcal", calories);
}
else
{
Console.WriteLine("Please choose correct gender Male(M) or Female(F).");
}
if (activityLevel == 0)
{
calories = Convert.ToInt32(calories * 1);
Console.WriteLine("Your daily calories are: {0} kcal", calories);
}
else if (activityLevel == 1)
{
calories = Convert.ToInt32(calories * 1.2);
Console.WriteLine("Your daily calories are: {0} kcal", calories);
}
else if (activityLevel == 2)
{
calories = Convert.ToInt32(calories * 1.375);
Console.WriteLine("Your daily calories are: {0} kcal", calories);
}
else if (activityLevel == 3)
{
calories = Convert.ToInt32(calories * 1.55);
Console.WriteLine("Your daily calories are: {0} kcal", calories);
}
else if (activityLevel == 4)
{
calories = Convert.ToInt32(calories * 1.725);
Console.WriteLine("Your daily calories are: {0} kcal", calories);
}
else if (activityLevel == 5)
{
calories = Convert.ToInt32(calories * 1.9);
Console.WriteLine("Your daily calories are: {0} kcal", calories);
}
else
{
Console.WriteLine("Please choose a number between 0 and 5");
}
}
答案 1 :(得分：0)
发生这种情况是因为您实际上是在每个块中创建新的int变量。当您定义变量并为其赋值时，该变量及其值仅在当前上下文中“存在”-为简单起见，请将该上下文视为直接父{}大括号之间的所有内容。因此，当您定义
if (gender == "m")
{
int calories = Convert.ToInt32(66.4730 + (13.7516 * weightKG) + (5.0033 * height) - (6.7550 * age));
// Console.WriteLine("Your daily calories are: {0}kcal",calories);
}
卡路里变量仅在if语句{}括号内可见。
如此简单的解决方法是在{}之外声明卡路里变量。
int baseCalories = 0;
if (gender == "m")
{
baseCalories = Convert.ToInt32(66.4730 + (13.7516 * weightKG) + (5.0033 * height) - (6.7550 * age));
// Console.WriteLine("Your daily calories are: {0}kcal",calories);
}
else if (gender == "f")
{
baseCalories = Convert.ToInt32(655.0955 + (9.5634 * weightKG) + (1.8496 * height) - (4.6756 * age));
// Console.WriteLine("Your daily calories are: {0} kcal", calories);
}
else
{
Console.WriteLine("Please choose correct gender Male(M) or Female(F).");
}
，然后在其他if语句中使用此baseCalories变量。
要了解有关变量范围的更多信息，请阅读例如this。
答案 2 :(得分：0)
关于您的问题（关于错误）。基本上，变量在声明它的块内可见。如果在if块内声明该变量，则仅在该if块内可见。如果在class块中声明它，则在该类及其方法内部，以及在使用正确的访问修饰符的情况下，在其他类中也将可见。
因此，如果需要访问变量，则需要根据其用法选择在何处声明它。
但是，这不是您遇到的唯一问题。您正在接受用户输入并直接使用它。这不是最佳实践。您需要先验证值，然后再使用它们。否则，您将要处理很多将在代码的每个点上引发的异常，并且应用程序越大，它将变得越糟。
以下几点将帮助您改善代码：
在使用前验证用户输入，这意味着您将用户输入存储在临时变量中，然后将其传递到验证逻辑中（如果通过了验证过程），然后将其值分配给原始变量。
为您的应用程序建模。 C＃是面向对象的编程语言。构建更易于阅读，维护和扩展的代码结构更加容易。例如，如果您的应用程序依赖于某些值（例如性别，年龄，身高，体重），为什么不创建一个将存储这些值的模型，然后可以在代码中来回传递该模型。
public class PersonInfo
{
public string Gender { get; set; }
public int Age { get; set; }
public int Height { get; set; }
public int Weight { get; set; }
public int ActivityLevel { get; set; }
public double Calories { get; set; }
}
有了这个，您将始终在代码中使用该模型，并且您将知道值存储在该模型内部，这可以使您的工作更加轻松。
使用Enum 枚举是有原因的。使用它会很有用。在您的情况下，您可以将其用于这样的输入类型：
public enum InputType { Age, Height, Weight, ActivityLevel }
不转换源值 您需要保持原样。如果需要显示不同类型的值，例如从小数到整数。您可以在运行时转换它们，但不要触碰源代码。这是因为您可能需要在代码中的其他地方重用源值。因此，如果您转换源代码，就会搞砸了。
使用适当的方法，有时，您会遇到需要使用实例循环的地步，但是由于某些原因，您只是跳过了这一需求。这可能会导致代码逻辑中的一些错误和问题。例如，您的应用程序需要年龄，身高，体重和活动水平才能计算卡路里。如果缺少其中之一，则公式错误，并且公式错误。如果仅一次获得该值，并且如果无效则从不返回，则根本没有理由使用该公式，因为这些值是错误的。因此，为此，您需要确保在运行公式之前先获得每个变量。您可以创建一个循环并跟踪用户输入，如果无效，则强制用户输入有效值。或者直接退出应用程序。
代码重用 即使您知道它不会在其他任何地方重复使用，也应始终以重复使用同一代码为目的进行编码。这意味着，您将使用部分代码并将其放置在易于重用和维护的位置。例如性别，您可以将其放入方法中并重新调用它。卡路里公式也可以用作方法，等等。
最后，我整理了这些要点的样本，以给出更多的直观想法，希望对您有所帮助。
// Person Information Model
public class PersonInfo
{
public string Gender { get; set; }
public int Age { get; set; }
public int Height { get; set; }
public int Weight { get; set; }
public int ActivityLevel { get; set; }
public double Calories { get; set; }
}
class Program
{
private static PersonInfo info = new PersonInfo();
public enum InputType { Age, Height, Weight, ActivityLevel }
static void Main(string[] args)
{
// default is null, to tell the application is invalid input
string _gender = null;
// keep the user inside this loop as long as the input is invalid.
while (_gender == null)
{
Console.WriteLine("Gender: Male(M)/Female(F)?");
_gender = GetGender(Console.ReadLine());
if (_gender == null)
Console.WriteLine("Gender has not been specified correctly. Please retype it.");
}
// it'll not go out of the loop until the user input is correct.
info.Gender = _gender;
// Create an array of inputs that you'll take from the user.
InputType[] inputs = { InputType.Age, InputType.Height, InputType.Weight, InputType.ActivityLevel };
bool hasError = false;
// Loop over the required inputs, and don't go to the next one until the user input a correct value.
for (int x = 0; x < inputs.Length; x++)
{
double userinput;
if (hasError)
x--;
if (inputs[x] != InputType.ActivityLevel)
{
Console.WriteLine("{0}? {1} ", inputs[x].ToString(), x);
userinput = GetInt(Console.ReadLine(), inputs[x]);
}
else
{
Console.WriteLine("How active are you?(Choose by inserting the number)");
Console.WriteLine("1.No exercise");
Console.WriteLine("2.Little to no exercise");
Console.WriteLine("3.Light exercise(1-3 days a week)");
Console.WriteLine("4.Moderate exercise(3-5 days a week");
Console.WriteLine("5.Heavy exercise(6-7days a week)");
// Console.WriteLine("6.Very heavy exercise(Twice per day, extra heavy workouts");
userinput = GetInt(Console.ReadLine(), InputType.ActivityLevel);
if (userinput >= 0 && userinput < 6)
{
info.ActivityLevel = (int)userinput;
info.Calories = GetCalories(info.Gender, info.Weight, info.Height, info.Age, info.ActivityLevel);
}
else
{
//reset input
userinput = -1;
Console.WriteLine("Please choose a number between 0 and 5");
}
}
if (userinput != -1)
{
SetValues((int)userinput, inputs[x]);
hasError = false;
}
else
{
Console.WriteLine("{0} has not been specified correctly. Please retype it.", inputs[x].ToString());
hasError = true;
}
}
// Now, you can show the user info with the calories as well.
Console.WriteLine("Your Gender\t\t:\t{0}", info.Gender);
Console.WriteLine("Your Age\t\t:\t{0}", info.Age);
Console.WriteLine("Your Height\t\t:\t{0}", info.Height);
Console.WriteLine("Your Weight\t\t:\t{0}", info.Weight);
Console.WriteLine("Your Activity Level\t:\t{0}", info.ActivityLevel);
Console.WriteLine("Your daily calories\t:\t{0} kcal", Math.Round(info.Calories));
Console.ReadLine();
}
public static string GetGender(string input)
{
if (!string.IsNullOrEmpty(input))
{
switch (input.ToLower())
{
case "m":
case "male":
return "m";
case "f":
case "female":
return "f";
default:
return null;
}
}
else
{
return null;
}
}
public static double GetActivityLevel(int level)
{
switch (level)
{
case 0:
return 1;
case 1:
return 1.2;
case 2:
return 1.375;
case 3:
return 1.55;
case 4:
return 1.725;
case 5:
return 1.9;
default:
return -1;
}
}
public static int GetInt(string input, InputType type)
{
if (!string.IsNullOrEmpty(input))
{
if (int.TryParse(input, out int result))
{
return result;
}
else
{
return -1;
}
}
else
{
Console.WriteLine(type.ToString() + " is empty");
return -1;
}
}
public static void SetValues(int input, InputType type)
{
switch (type)
{
case InputType.Age:
info.Age = input;
break;
case InputType.Weight:
info.Weight = input;
break;
case InputType.Height:
info.Height = input;
break;
}
}
public static double GetCalories(string gender, int weight, int height, int age, int activityLevel)
{
if (string.IsNullOrEmpty(gender))
{
Console.WriteLine("Gender has not been specified");
return -1;
}
else
{
double _cal;
var _level = GetActivityLevel(activityLevel);
if (gender == "m")
_cal = (66.4730 + (13.7516 * weight) + (5.0033 * height) - (6.7550 * age));
else
_cal = (655.0955 + (9.5634 * weight) + (1.8496 * height) - (4.6756 * age));
//check first Activity Level, if is it -1 then it's invalid input, those it'll return it.
return _level != -1 ? _cal * _level : -1;
}
}