Visual c# 2010学习笔记6.doc

Convert.ToInt32、int.Parse（Int32.Parse）、int.TryParse、(int) 四者都可以解释为将类型转换为 int，那它们的区别是什么呢？Convert.ToInt32 与 int.Parse 较为类似，实际上 Convert.ToInt32 内部调用了 int.Parse：Convert.ToInt32 参数为 null 时，返回 0； int.Parse 参数为 null 时，抛出异常。 Convert.ToInt32 参数为 时，抛出异常； int.Parse 参数为 时，抛出异常。 Convert.ToInt32 可以转换的类型较多； int.Parse 只能转换数字类型的字符串。 int.TryParse 与 int.Parse 又较为类似，但它不会产生异常，转换成功返回 true，转换失败返回 false。最后一个参数为输出值，如果转换失败，输出值为 0。退出按钮的语法private void quitClick(object sender, RoutedEventArgs e) this.Close(); 例： private void divideValues() int lhs = int.Parse(lhsOperand.Text); int rhs = int.Parse(rhsOperand.Text); int outcome; outcome = lhs / rhs; expression.Text = lhsOperand.Text + / + rhsOperand.Text; result.Text = outcome.ToString(); 解析：文本框控件的Text属性包含的是字符串，必须将字符串转换为整数。ToString是 .NET Framework 中主要的格式化方法。它将对象转换为其字符串表现形式，使它适合于显示。.NET Framework中的每一个类都有一个ToString方法，用途是将一个对象转换为相应的字符串形式。private void calculateClick(object sender, RoutedEventArgs e) try if (bool)addition.IsChecked) addValues(); else if (bool)subtraction.IsChecked) subtractValues(); else if (bool)multiplication.IsChecked) multiplyValues(); else if (bool)division.IsChecked) divideValues(); else if (bool)remainder.IsChecked) remainderValues();/IsChecked表示是否被选中 catch (Exception caught) expression.Text = ; result.Text = caught.Message; 抛出异常：如果try中的命令执行条件都不满足的话，就执行catch，而不执行try中的语句，则表明没有选择运算方法，所以expression没有为空。而result.Text = caught.Message;为通用抛出异常语句。例：int x = 42; Console.WriteLine(x+); int y = 42; Console.WriteLine(+y); Console.ReadLine();结果：解析：在表达式x+中，它首先返回x的值，再执行+；再+y中，首先执行+，再返回y的值。例：var myVariable = 99;var myOtherVariable = “Hello”;解析：从例中可以看出，我们并没有具体声明myVariable和myOtherVariable的类型，只是用var代替，但是却可以用var根据后面的赋值来推算这个类型。这两个变量被称作隐式类型变量。var只是在声明变量的时候可以为我们提供一些方便，但是当变量一旦声明完后，就只能将编译器推断的这种类型的值赋给它。建议：除非万不得已，不要使用隐式变量，还是用显式变量。方法：void show(int x)return;/该语句可要可不要。private int addValues(int leftHandSide, int rightHandSide) expression.Text = leftHandSide.ToString() + + + rightHandSide.ToString(); return leftHandSide + rightHandSide; 改进上面例子的方法，由不返回值变成返回值的方法。可以省去int outcome语句，而result则被单独编写为一个方法，故此可以省略大量语句。using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Windows;using System.Windows.Controls;using System.Windows.Data;using System.Windows.Documents;using System.Windows.Input;using System.Windows.Media;using System.Windows.Media.Imaging;using System.Windows.Navigation;using System.Windows.Shapes;namespace MathsOperators / / Interaction logic for MainWindow.xaml / public partial class MainWindow : Window public MainWindow() InitializeComponent(); private void calculateClick(object sender, RoutedEventArgs e) int calculatedValue = 0; try int leftHandSide = System.Int32.Parse(lhsOperand.Text); int rightHandSide = System.Int32.Parse(rhsOperand.Text); if (addition.IsChecked.HasValue & addition.IsChecked.Value) calculatedValue = addValues(leftHandSide, rightHandSide); showResult(calculatedValue); else if (subtraction.IsChecked.HasValue & subtraction.IsChecked.Value) calculatedValue = subtractValues(leftHandSide, rightHandSide); showResult(calculatedValue); else if (multiplication.IsChecked.HasValue & multiplication.IsChecked.Value) calculatedValue = multiplyValues(leftHandSide, rightHandSide); showResult(calculatedValue); else if (division.IsChecked.HasValue & division.IsChecked.Value) calculatedValue = divideValues(leftHandSide, rightHandSide); showResult(calculatedValue); else if (remainder.IsChecked.HasValue & remainder.IsChecked.Value) calculatedValue = remainderValues(leftHandSide, rightHandSide); showResult(calculatedValue); catch (Exception caught) expression.Text = ; result.Text = caught.Message; private int addValues(int leftHandSide, int rightHandSide) expression.Text = leftHandSide.ToString() + + + rightHandSide.ToString(); return leftHandSide + rightHandSide; private int subtractValues(int leftHandSide, int rightHandSide) expression.Text = leftHandSide.ToString() + - + rightHandSide.ToString(); return leftHandSide - rightHandSide; private int multiplyValues(int leftHandSide, int rightHandSide) expression.Text = leftHandSide.ToString() + * + rightHandSide.ToString(); return leftHandSide * rightHandSide; private int divideValues(int leftHandSide, int rightHandSide) expression.Text = leftHandSide.ToString() + / + rightHandSide.ToString(); return leftHandSide / rightHandSide; /private void divideValues() / / int lhs = int.Parse(lhsOperand.Text); / int rhs = int.Parse(rhsOperand.Text); / int outcome; / outcome = lhs / rhs; / expression.Text = lhsOperand.Text + / + rhsOperand.Text; / result.Text = outcome.ToString(); / private int remainderValues(int leftHandSide, int rightHandSide) expression.Tex