18: Creating Windows Applications | in C#.NET

Generator Code 128 Code Set A in C#.NET 18: Creating Windows Applications |

"Please enter a number", "Format Error", MessageBoxButtons.OK, MessageBoxIcon.Error); txtAmount.Clear( ); }

The code for the Form1.cs file is shown in Example A-55.

Example A-55. One solution to Exercise 18-3

using using using using using using using using System; System.Collections.Generic; System.ComponentModel; System.Data; System.Drawing; System.Linq; System.Text; System.Windows.Forms;

namespace Exercise_18_3 { public partial class Form1 : Form { public Form1( ) { InitializeComponent( ); } private void btnSubmit_Click(object sender, EventArgs e) { try { double tax = Convert.ToDouble(txtAmount.Text) * (Convert.ToDouble(nudTax.Value) * 0.01); double total = Convert.ToDouble(txtAmount.Text) + tax; string resultString = "Tax on $" + txtAmount.Text + " at " + nudTax.Value + "% is $" + tax.ToString("F") + ".\nThe total is $" + total.ToString("F") + "."; lblResult.Text = resultString; } catch (FormatException) { DialogResult error = MessageBox.Show( "Please enter a number", "Format Error",

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Example A-55. One solution to Exercise 18-3 (continued)

MessageBoxButtons.OK, MessageBoxIcon.Error); txtAmount.Clear( ); } } private void btnClear_Click(object sender, EventArgs e) { txtAmount.Clear( ); } } }

Solution to Question 19-1. XAML is a subset of XML intended for use with WPF. It has a schema created by Microsoft with elements for Windows applications. Solution to Question 19-2. You can edit the properties of a XAML element in the Properties window, or directly in the XAML window. Either way, any changes you make will immediately be reflected in the Design window. Solution to Question 19-3. The x: refers to the current namespace for the application. You need to use it to define properties that will be used elsewhere in the application. Solution to Question 19-4. The Margin property takes four comma-separated values, representing the distance, in units, from the left, top, right, and bottom of the window. A zero for any of the values indicates that the distance is not fixed. Solution to Question 19-5. When you have a number of controls of the same type, you could style each control individually, but it would be easier to define a Style element as a resource. Solution to Question 19-6. The TargetType property, applied to a Style, restricts the style to a certain type of control. Solution to Question 19-7. The Trigger element is used for handling events within the XAML file. Solution to Question 19-8. Animations are contained in Storyboard controls.

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Solution to Question 19-9. A Trigger element can contain a storyboard action, but not a Storyboard element directly. The BeginStoryboard element provides that action, and can contain a storyboard. Solution to Question 19-10. The DataContext property allows an element to access a data source.

Solution to Exercise 19-1. We ll start things off simply. Create a WPF application with several Button and TextBox controls. Set the TextBox controls to have white text on a blue background, and the Button controls to have green text on a gray background. This exercise isn t particularly challenging, but it does enable you to practice the use of styles. You first create a new WPF project. Then drag several Button and TextBox controls onto the form; it doesn t matter where. You could certainly copy the same Style attributes to each control, but that s a pain. Instead, you should define a style resource for each control in the Windows.Resources section. Remember to give each style an x:Key property so that you can reference it later from within the controls, and remember to have each control reference the style as a StaticResource. Example A-56 shows the full XAML file for this exercise.

Example A-56. One solution to Exercise 19-1

<Window x:Class="Exercise_19_1.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="Window1" Height="300" Width="300"> <Window.Resources> <Style x:Key="buttonStyle" TargetType="Button"> <Setter Property="Foreground" Value="White" /> <Setter Property="Background" Value="Blue" /> </Style> <Style x:Key="textboxStyle" TargetType="TextBox"> <Setter Property="Foreground" Value="Green" /> <Setter Property="Background" Value="Gray" /> </Style> </Window.Resources> <Grid> <TextBox Style="{StaticResource textboxStyle}" Height="23" Margin="19,56,139,0" Name="textBox1" VerticalAlignment="Top">TextBox1</TextBox> <Button Style="{StaticResource buttonStyle}" Height="23" HorizontalAlignment="Right" Margin="0,38,51,0" Name="button1" VerticalAlignment="Top" Width="75">Buttton1</Button> <Button Style="{StaticResource buttonStyle}" HorizontalAlignment="Left" Margin="34,115,0,124" Name="button2" Width="75">Button2</Button> <TextBox Style="{StaticResource textboxStyle}" HorizontalAlignment="Right" Margin="0,109,3,130" Name="textBox2" Width="120">TextBox2</TextBox>

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