[英]Button doesn't make value appear in textBox
I want 2 textBoxes to show numbers after I press a button, but when I press a button, one textBox shows number in it and the second doesn't. 我想2个文本框后我按下一个按钮显示的数字,但是当我按下一个按钮,了一个TextBox显示其数量和第二个没有。
private void Calculating(object sender, EventArgs e)
{
if (textBox6.Text != "")
{
rutr = Double.Parse(textBox6.Text);
rutd = rutr * 2;
textBox7.Text = (rutd).ToString();
textBox8.Text = (3 / 4 * pi * rutr * rutr * rutr).ToString();
}
}
The textBox8
doesn't show correct number. textBox8
没有显示正确的数字。
The very cause of the misbehavior is integer division : 3 / 4 == 0
should be 行为不当的根本原因是整数除法 :
3 / 4 == 0
应该是
// The formula seems to be a volume of a sphere: 3/4 * Pi * r**3
// It's a physical world, that's why 3.0 - double, not 3M - decimal
textBox8.Text = (3.0 / 4.0 * pi * rutr * rutr * rutr).ToString();
please, notice floating point 3.0
value instead of integer 3
. 请注意浮点数
3.0
而不是整数 3
。 Another suggestion is to use double.TryParse
: if we can parse user input ( textBox6.Text
) then do it and compute 另一个建议是使用
double.TryParse
:如果我们可以解析用户输入( textBox6.Text
),然后进行计算
private void Calculating(object sender, EventArgs e) {
double rutr = 0.0;
// If we can parse textBox6.Text into double rutr
if (double.TryParse(textBox6.Text, out rutr)) {
rutd = rutr * 2;
textBox7.Text = (rutd).ToString();
textBox8.Text = (3.0 / 4.0 * pi * rutr * rutr * rutr).ToString();
}
}
Edit : Technically, it's possible to produce blank ( ""
) in the textBox8
, see comments below (it's an interesting problem itself). 编辑 :从技术上讲,有可能在
textBox8
产生空白 ( ""
),请参阅下面的评论(这本身就是一个有趣的问题)。 Here's the code 这是代码
using System.Globalization;
...
CultureInfo ci = (CultureInfo.CurrentCulture.Clone() as CultureInfo);
// The idea: double.NaN will be displayed as blank
ci.NumberFormat.NaNSymbol = "";
CultureInfo.CurrentCulture = ci;
double pi = Math.Sqrt(-1); // pi is double.NaN - imaginary unit
...
// 0 * NaN * rutr * rutr * rutr == NaN which is printed as empty string
textBox8.Text = (3 / 4 * pi * rutr * rutr * rutr).ToString();
Here we exploit the fact that, 0 * double.NaN == double.NaN
. 在这里,我们利用以下事实:
0 * double.NaN == double.NaN
。 However, I don't believe in this kind of error 但是,我不相信这种错误
You should use a suffix to tell the compiler that the numeric literals are not treated as int. 您应该使用后缀来告诉编译器数字文字不被视为int。
textBox8.Text = (3M / 4M * pi * rutr * rutr * rutr).ToString();
https://docs.microsoft.com/en-US/dotnet/csharp/language-reference/keywords/decimal https://docs.microsoft.com/en-US/dotnet/csharp/language-reference/keywords/decimal
Here is a list of possible suffixes: 以下是可能的后缀列表:
F: float D: double U: uint L: long UL: ulong M: decimal F:浮点数D:双精度U:uint L:长UL:ulong M:十进制
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