在 C# 中从两个整数创建百分比值的最佳方法是什么？
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What's the best way to create a percentage value from two integers in C#?
提问by Vaccano
I have two integers that I want to divide to get a percentage.
我有两个整数要除以得到一个百分比。
This is what I have right now:
这就是我现在所拥有的：
int mappedItems = someList.Count(x => x.Value != null);
int totalItems = someList.Count();
(int)(((double)mappedItems /(double) totalItems) * 100)
This gives the right answer. But that is a lot of casting to do something as simple as get a percentage between two numbers.
这给出了正确的答案。但这需要大量的转换来做一些简单的事情，比如获得两个数字之间的百分比。
Is there a better way to do this? Something that does not involve casting?
有一个更好的方法吗？不涉及铸造的东西？
采纳答案by John Feminella
How about just mappedItems * 100.0 / totalItemsand casting this to the appropriate type?
如何mappedItems * 100.0 / totalItems将其转换为适当的类型？
回答by Mick
You could use (mappedItems * 100) / totalItems but this would always round down. The method that you have used is better. Why not wrap the code up as a method?
您可以使用 (mappedItems * 100) / totalItems 但这将始终向下取整。您使用的方法更好。为什么不把代码包装成一个方法呢？
回答by tster
Well, assuming your counts are smaller than int.MaxValue:
好吧，假设您的计数小于 int.MaxValue：
int percent = mappedItems * 100 / totalItems;
回答by oefe
If you just wanted to avoid the casts, you could write:
如果你只是想避免强制转换，你可以写：
(100 * mappedItems) / totalItems
but that will quickly overflow when mappedItems > int.MaxValue / 100.
但是当mappedItems > int.MaxValue / 100.
And both methods round the percentage down. To get correct rounding, I would keep the result as a double:
并且这两种方法都将百分比向下舍入。为了获得正确的四舍五入，我会将结果保留为双精度：
((double)mappedItems /(double) totalItems) * 100
回答by Guffa
You can get a correctly rounded result using only integer operations:
仅使用整数运算即可获得正确舍入的结果：
int percent = (200 * mappedItems + 1) / (totalItems * 2);
By multiplyingby two, adding one and dividing by two, you are effectively adding a half. This makes the integer division do a rounding instead of truncating.
通过乘以二、加一和除以二，您实际上是加了一半。这使得整数除法进行舍入而不是截断。
回答by ChrisF
Just to add that as you've got ints and want to calculate the percentage (a floating point value) you are going to haveto do casting. Whether it's explicit as in C# or implicit as in some scripting languages the cast will still happen. It's better to make it explicit.
只是补充一点，因为您有ints 并且想要计算您将不得不进行转换的百分比（浮点值）。无论是在 C# 中是显式还是在某些脚本语言中是隐式的，转换仍然会发生。最好说清楚。
If you want fewer casts per line of code you could write:
如果您希望每行代码的转换次数更少，您可以编写：
double mappedItems = (double)someList.Count(x => x.Value != null);
double totalItems = (double)someList.Count();
double percentage = (mappedItems / totalItems) * 100.0);
Though as others have pointed out - check for totalItemsbeing 0 (preferably before casting to double) to avoid a divide by zero.
尽管正如其他人指出的那样 - 检查是否为totalItems0（最好在强制转换为 double 之前）以避免被零除。
回答by Brad Parks
try this:
尝试这个：
int mappedItems = someList.Count(x => x.Value != null);
int totalItems = someList.Count();
int percent = Convert.ToInt32(complete * 100.0 / total);
in this example, you'd get result being "50"
在这个例子中，你会得到结果是“50”
int mappedItems = 14;
int totalItems = 28;
int result = Convert.ToInt32(mappedItems * 100.0 / totalItems);
// result is 50
回答by dragonroot
The right integer-only way to get percentage with proper rounding is:
通过适当的舍入获得百分比的正确整数方法是：
int result = ( mappedItems * 200 + totalItems ) / ( totalItems * 2 );
How do we get there? If we do this thing in floating point, it would be Math.Floor( mappedItems * 100.0 / totalItems + 0.5 ). We need to transform this formula to be integer-only by multiplying and dividing 0.5 by totalItems, then moving 0.5 * totalItems into dividend, and then multiplying both dividend and divisor by 2 to make fractions go away:
我们怎么去那里？如果我们用浮点数做这件事，那就是Math.Floor( mappedItems * 100.0 / totalItems + 0.5 ). 我们需要通过将 0.5 乘以和除以 totalItems，然后将 0.5 * totalItems 移动到被除数，然后将被除数和除数都乘以 2 来使分数消失，从而将这个公式转换为仅整数：
mappedItems * 100.0 / totalItems + 0.5 => mappedItems * 100.0 / totalItems + totalItems * 0.5 / totalItems => ( mappedItems * 100.0 + 0.5 * totalItems ) / totalItems => ( mappedItems * 200.0 + totalItems ) / ( totalItems * 2 ).
映射项目 * 100.0 / 总项目 + 0.5 => 映射项目 * 100.0 / 总项目 + 总项目 * 0.5 / 总项目 => ( 映射项目 * 100.0 + 0.5 * 总项目 ) / 总项目 => (映射项目 * 200.0 + 总项目 *) / (
At this point the formula is integer-only. When we do integer division, we get floored result, so the integer-only result is equivalent to the mentioned floating-point one.
此时，公式仅为整数。当我们做整数除法时，我们得到了地板结果，所以只有整数的结果等价于提到的浮点数。
