只读值的优雅解决方案
本文关键字：解决方案 只读 | 更新日期: 2023-09-27 18:06:21
我正在开发一个WPF应用程序，它的窗口大小和组件位置必须在初始化时动态计算，因为它们是基于我使用的主要UserControl大小和其他一些次要大小设置。因此，目前，我已经将这些常量值放置在我的窗口代码中，如下所示:
public const Double MarginInner = 6D;
public const Double MarginOuter = 10D;
public const Double StrokeThickness = 3D;
public static readonly Double TableHeight = (StrokeThickness * 2D) + (MarginInner * 3D) + (MyUC.RealHeight * 2.5D);
public static readonly Double TableLeft = (MarginOuter * 3D) + MyUC.RealHeight + MarginInner;
public static readonly Double TableTop = MarginOuter + MyUC.RealHeight + MarginInner;
public static readonly Double TableWidth = (StrokeThickness * 2D) + (MyUC.RealWidth * 6D) + (MarginInner * 7D);
public static readonly Double LayoutHeight = (TableTop * 2D) + TableHeight;
public static readonly Double LayoutWidth = TableLeft + TableWidth + MarginOuter;
然后，我在XAML中使用它们，如下所示:
<Window x:Class="MyNS.MainWindow" ResizeMode="NoResize" SizeToContent="WidthAndHeight">
<Canvas x:Name="m_Layout" Height="{x:Static ns:MainWindow.LayoutHeight}" Width="{x:Static ns:MainWindow.LayoutWidth}">
嗯…没什么可说的。它的工作原理……但是它看起来太丑了，我想知道是否有更好的解决方案。我不知道……也许是一个设置文件，绑定，内联XAML计算或其他…一些能让它看起来更好的东西
我通常把所有静态我的应用程序设置在一个单一的静态或单例类称为通用的东西，如ApplicationSettings(或MainWindowSettings，如果值仅由MainWindow使用)
如果这些值是用户可配置的，那么它们会放在app.config中，并被加载到静态类的构造函数中。如果没有，我就在静态类中硬编码它们，以便以后很容易找到/更改。
public static class ApplicationSettings
{
public static Double MarginInner { get; private set; }
public static Double MarginOuter { get; private set; }
public static Double StrokeThickness { get; private set; }
static ApplicationSettings()
{
MarginInner = 6D;
MarginOuter = 10D;
StrokeThickness = 3D;
}
}
对于XAML中的计算值，我通常使用我编写的MathConverter，它允许我编写带有数学表达式的绑定，并将要使用的值传递给它。
我在我的博客上发布的版本只是一个IValueConverter，但它很容易扩展到IMultiValueConverter，所以它可以接受多个绑定值。
<Setter Property="Height">
<Setter.Value>
<MultiBinding Converter="{StaticResource MathMultiConverter}"
ConverterParameter="(@VALUE1 * 2D) + (@VALUE2 * 3D) + (@VALUE3 * 2.5D)">
<Binding RelativeSource="{x:Static ns:ApplicationSettings.StrokeThickness }" />
<Binding RelativeSource="{x:Static ns:ApplicationSettings.MarginInner}" />
<Binding ElementName="MyUc" Path="ActualHeight" />
</MultiBinding>
</Setter.Value>
</Setter>
通常我会将所有这些混乱的XAML隐藏在某个样式中，这样它就不会使我的主XAML代码混乱，并且只在需要的地方应用样式。
这是我为IMultiValueConvter使用的转换器代码的副本
// Does a math equation on a series of bound values.
// Use @VALUEN in your mathEquation as a substitute for bound values, where N is the 0-based index of the bound value
// Operator order is parenthesis first, then Left-To-Right (no operator precedence)
public class MathMultiConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
// Remove spaces
var mathEquation = parameter as string;
mathEquation = mathEquation.Replace(" ", "");
// Loop through values to substitute placeholders for values
// Using a backwards loop to avoid replacing something like @VALUE10 with @VALUE1
for (var i = (values.Length - 1); i >= 0; i--)
mathEquation = mathEquation.Replace(string.Format("@VALUE{0}", i), values[i].ToString());
// Return result of equation
return MathConverterHelpers.RunEquation(ref mathEquation);
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
public static class MathConverterHelpers
{
private static readonly char[] _allOperators = new[] { '+', '-', '*', '/', '%', '(', ')' };
private static readonly List<string> _grouping = new List<string> { "(", ")" };
private static readonly List<string> _operators = new List<string> { "+", "-", "*", "/", "%" };
public static double RunEquation(ref string mathEquation)
{
// Validate values and get list of numbers in equation
var numbers = new List<double>();
double tmp;
foreach (string s in mathEquation.Split(_allOperators))
{
if (s != string.Empty)
{
if (double.TryParse(s, out tmp))
{
numbers.Add(tmp);
}
else
{
// Handle Error - Some non-numeric, operator, or grouping character found in string
throw new InvalidCastException();
}
}
}
// Begin parsing method
EvaluateMathString(ref mathEquation, ref numbers, 0);
// After parsing the numbers list should only have one value - the total
return numbers[0];
}
// Evaluates a mathematical string and keeps track of the results in a List<double> of numbers
private static void EvaluateMathString(ref string mathEquation, ref List<double> numbers, int index)
{
// Loop through each mathemtaical token in the equation
string token = GetNextToken(mathEquation);
while (token != string.Empty)
{
// Remove token from mathEquation
mathEquation = mathEquation.Remove(0, token.Length);
// If token is a grouping character, it affects program flow
if (_grouping.Contains(token))
{
switch (token)
{
case "(":
EvaluateMathString(ref mathEquation, ref numbers, index);
break;
case ")":
return;
}
}
// If token is an operator, do requested operation
if (_operators.Contains(token))
{
// If next token after operator is a parenthesis, call method recursively
string nextToken = GetNextToken(mathEquation);
if (nextToken == "(")
{
EvaluateMathString(ref mathEquation, ref numbers, index + 1);
}
// Verify that enough numbers exist in the List<double> to complete the operation
// and that the next token is either the number expected, or it was a ( meaning
// that this was called recursively and that the number changed
if (numbers.Count > (index + 1) &&
(double.Parse(nextToken) == numbers[index + 1] || nextToken == "("))
{
switch (token)
{
case "+":
numbers[index] = numbers[index] + numbers[index + 1];
break;
case "-":
numbers[index] = numbers[index] - numbers[index + 1];
break;
case "*":
numbers[index] = numbers[index] * numbers[index + 1];
break;
case "/":
numbers[index] = numbers[index] / numbers[index + 1];
break;
case "%":
numbers[index] = numbers[index] % numbers[index + 1];
break;
}
numbers.RemoveAt(index + 1);
}
else
{
// Handle Error - Next token is not the expected number
throw new FormatException("Next token is not the expected number");
}
}
token = GetNextToken(mathEquation);
}
}
// Gets the next mathematical token in the equation
private static string GetNextToken(string mathEquation)
{
// If we're at the end of the equation, return string.empty
if (mathEquation == string.Empty)
{
return string.Empty;
}
// Get next operator or numeric value in equation and return it
string tmp = "";
foreach (char c in mathEquation)
{
if (_allOperators.Contains(c))
{
return (tmp == "" ? c.ToString() : tmp);
}
else
{
tmp += c;
}
}
return tmp;
}
}
但是老实说，如果这些值只在一个形式中使用，那么我就在视图后面的代码中设置Loaded事件中的值:)
把这些静态的放到app.config中，它们在那里会更干净。
使用app.config，你首先必须有一个对System.Configuration的引用。
那么你可以这样做(可能涉及到一些类型转换):
ConfigurationManager.AppSettings["MarginInner"];
<configuration>
<appsettings>
<add key="MarginInner" value="6D" />
</appsettings>
</configuration>
然后可能有一个静态类来保存动态计算，例如:
public class CalculationHelper
{
//your dynamic properties in here
}
mattytommo的答案只针对您拥有的常量值(边距和笔画厚度)，而不是计算字段。
我将结合Matty所说的，添加一个从app.config文件中检索常量值的设置类，并执行所需的适当计算，然后我可以引用XAML
中的适当属性。。
{ Settings.MainWindow.LayoutWidth }
编辑:
看起来Matty也有同样的想法，尽管他在我发帖之间编辑;)