可變越界

我剛剛學習C＃，我創建了一個簡單的程序來獲取人BMI，但我遇到的問題是，雖然我的程序可以獲取剩餘的變量，但它無法獲取一。當我運行它時會發生什麼，它說它不能獲得weightclass變量，因爲它超出了界限，而如果我從代碼的console.writeline部分刪除了weightclass，那麼程序將運行時沒有問題。可變越界

Console.WriteLine("what's your weight in pounds"); 
    string weight = Console.ReadLine(); 
    float weighnum = Single.Parse(weight); 
    weight = weighnum.ToString(); 
    Console.WriteLine("what's your height in inches"); 
    string height = Console.ReadLine(); 
    float heightnum = Single.Parse(weight); 
    height = heightnum.ToString(); 
    Console.WriteLine("what's your gender"); 
    string gender = Console.ReadLine(); 



    float bmi = ((weighnum)/((heightnum) * (heightnum)) * 703); 
    if (bmi < 17.5 & gender == "f") 
    { string weightclass = "anorexic"; } 
    else if (bmi > 17.5 & bmi < 19.1 & gender == "f") 
    { string weightclass = "underweight"; } 
    else if (bmi > 19.1 & bmi <25.8 & gender == "f") 
    { string weightclass = "normal range"; } 
    else if (bmi > 25.8 & bmi < 27.3 & gender == "f") 
    { string weightclass = "marginally overweight"; } 
    else if (bmi > 27.3 & bmi < 32.3 & gender == "f") 
    { string weightclass = "overweight"; } 
    else if (bmi > 32.3 & bmi < 35 & gender == "f") 
    { string weightclass = "obese"; } 
    else if (bmi > 35 & bmi < 40 & gender == "f") 
    { string weightclass = "severely obese"; } 
    else if (bmi > 40 & bmi < 50 & gender == "f") 
    { string weightclass = "morbidly obese"; } 
    else if (bmi > 50 & gender == "f") 
    { string weightclass = "super obese"; } 
    else if (bmi < 20 & gender == "m") 
    { string weightclass = "underweight"; } 
    else if (bmi >= 20 & bmi <= 25 & gender == "m") 
    { string weightclass = "normal range"; } 
    else if (bmi > 25 & gender == "m") 
    { string weightclass = "marginally overweight"; } 
    else if (bmi < 20 & gender == "m") 
    { string weightclass = "overweight"; } 
    else if (bmi >= 20 & bmi <= 25 & gender == "m") 
    { string weightclass = "obese"; } 
    else if (bmi > 25 & gender == "m") 
    { string weightclass = "severely obese"; } 
    else if (bmi < 20 & gender == "m") 
    { string weightclass = "morbidly obese"; } 
    else if (bmi >= 20 & bmi <= 25 & gender == "m") 
    { string weightclass = "super obese"; } 

    Console.WriteLine("your bmi is " + bmi + " this means that you are " + weightclass); 




    } 
} 
}

來源

2015-10-05 Matt Parkinson

當您提出這些問題時，請嘗試儘可能使錯誤文本具體。你應該得到更像「名稱」variablename「在當前上下文中不存在」的東西，越界意味着你在索引數組時遇到了錯誤。 –

您需要找到一種更好地組織代碼的方法，因爲不清楚是否所有輸入組合都由if語句處理。它看起來像不是：沒有if語句觸發器的組合，所以* weightclass *沒有被賦值。至少可以防止這種情況的一種方法是創建* weightclass *，並在代碼頂部爲它指定一個值，如*「unknown」*。這樣你會立即看到輸入的數值組合在問題中滑動。 –

你必須將你的weightclass -variablke聲明任何else - 阻塞外：發生

float bmi = ((weighnum)/((heightnum) * (heightnum)) * 703); 
string weightclass = null; 

if (bmi < 17.5 & gender == "f") 
{ weightclass = "anorexic"; } 
else if (bmi > 17.5 & bmi < 19.1 & gender == "f") 
...

的問題，因爲每一個變量綁定到其範圍在聲明。當你在一個else塊中聲明一個塊時，你不能在特定範圍內訪問它。 Further information on scopes can be found here

來源

2015-10-05 11:39:43 HimBromBeere

啊，謝謝我嘗試將它移到外面，但我必須將它移得太遠。 –

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