C# Tutorial 24
In this part of my C# video tutorial I show how to make a Paint App, and then we look at Drawing Lines, Ellipses, and Rectangles using Canvas. We’ll be using System.Windows.Shapes in this tutorial. They are great to work with because they respond to events just like other WPF components.
For best results take notes on the cheat sheet provided below as you watch and leave any questions you have.
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Code & Cheat Sheet
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// ---------- MainWindow.xaml ---------- <Window x:Class="WpfTutorial.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:local="clr-namespace:WpfTutorial" xmlns:sys="clr-namespace:System;assembly=mscorlib" mc:Ignorable="d" Title="MainWindow" Height="350" Width="525" SizeToContent="WidthAndHeight" Topmost="False" WindowState="Normal" Icon="./Resources/favicon.ico"> <DockPanel> <!-- Click the toolbar and select Common -> Items -> ... Set Border Brush RGB to 150 Height to 50 and Width to 80 Add a Content name for Line, Ellipse and Rectangle for each Select all radiobuttons and give the group name ShapeGroup --> <ToolBar Name="MyToolbar" DockPanel.Dock="Top" Height="50"> <RadioButton Name="LineButton" BorderBrush="#FF969696" Content="Line" Height="50" Width="77" GroupName="ShapeGroup" Click="LineButton_Click" IsChecked="True"/> <RadioButton Name="EllipseButton" BorderBrush="#FF969696" Content="Ellipse" Height="50" Width="80" GroupName="ShapeGroup" Click="EllipseButton_Click"/> <RadioButton Name="RectangleButton" BorderBrush="#FF969696" Content="Rectangle" Height="50" Width="80" GroupName="ShapeGroup" Click="RectangleButton_Click"/> </ToolBar> <Canvas Name="MyCanvas" Background="AntiqueWhite" Height="300" Width="525" MouseDown="MyCanvas_MouseDown" MouseUp="MyCanvas_MouseUp" MouseMove="MyCanvas_MouseMove"> <!-- Draw a line --> <Line X1="10" Y1="10" X2="50" Y2="50" Stroke="Black" StrokeThickness="4" /> <!-- Draw an Ellipse --> <Ellipse Fill="Yellow" Height="50" Width="100" StrokeThickness="2" Stroke="Black" Canvas.Left="100" Canvas.Top="20"/> <!-- Draw a Rectangle --> <Rectangle Fill="Blue" Height="50" Width="100" Canvas.Left="240" Canvas.Top="20"/> </Canvas> </DockPanel> </Window> // ---------- MainWindow.xaml.cs ---------- using Microsoft.Win32; using System; using System.Collections.Generic; using System.IO; using System.Windows; using System.Windows.Controls; using System.Windows.Input; using System.Windows.Media; using System.Windows.Shapes; namespace WpfTutorial { /// <summary> /// Interaction logic for MainWindow.xaml /// </summary> // For generating a limited number of 2D // vector images you can use // System.Windows.Shapes // Shapes created this way respond to // events like other WPF components public partial class MainWindow : Window { // Define enum for all 3 shapes private enum MyShape { Line, Ellipse, Rectangle } // Define the current shape used private MyShape currShape; public MainWindow() { InitializeComponent(); } private void LineButton_Click(object sender, RoutedEventArgs e) { currShape = MyShape.Line; } private void EllipseButton_Click(object sender, RoutedEventArgs e) { currShape = MyShape.Ellipse; } private void RectangleButton_Click(object sender, RoutedEventArgs e) { currShape = MyShape.Rectangle; } Point start; Point end; private void MyCanvas_MouseDown(object sender, MouseButtonEventArgs e) { // Get the X & Y of where mouse is 1st clicked start = e.GetPosition(this); } private void MyCanvas_MouseUp(object sender, MouseButtonEventArgs e) { // Draw the correct shape switch (currShape) { case MyShape.Line: DrawLine(); break; case MyShape.Ellipse: DrawEllipse(); break; case MyShape.Rectangle: DrawRectangle(); break; default: return; } } private void MyCanvas_MouseMove(object sender, MouseEventArgs e) { // Update the X & Y as the mouse moves if (e.LeftButton == MouseButtonState.Pressed) { end = e.GetPosition(this); } } // Sets and draws line after mouse is released private void DrawLine() { Line newLine = new Line() { Stroke = Brushes.Blue, X1 = start.X, Y1 = start.Y - 50, X2 = end.X, Y2 = end.Y - 50 }; MyCanvas.Children.Add(newLine); } // Sets and draws ellipse after mouse is released private void DrawEllipse() { Ellipse newEllipse = new Ellipse() { Stroke = Brushes.Green, Fill = Brushes.Red, StrokeThickness = 4, Height = 10, Width = 10 }; // If the user the user tries to draw from // any direction then down and to the right // you'll get an error unless you use if // to change Left & TopProperty and Height // and Width accordingly if (end.X >= start.X) { // Defines the left part of the ellipse newEllipse.SetValue(Canvas.LeftProperty, start.X); newEllipse.Width = end.X - start.X; } else { newEllipse.SetValue(Canvas.LeftProperty, end.X); newEllipse.Width = start.X - end.X; } if (end.Y >= start.Y) { // Defines the top part of the ellipse newEllipse.SetValue(Canvas.TopProperty, start.Y - 50); newEllipse.Height = end.Y - start.Y; } else { newEllipse.SetValue(Canvas.TopProperty, end.Y - 50); newEllipse.Height = start.Y - end.Y; } MyCanvas.Children.Add(newEllipse); } // Sets and draws rectangle after mouse is released private void DrawRectangle() { Rectangle newRectangle = new Rectangle() { Stroke = Brushes.Orange, Fill = Brushes.Blue, StrokeThickness = 4 }; if (end.X >= start.X) { // Defines the left part of the rectangle newRectangle.SetValue(Canvas.LeftProperty, start.X); newRectangle.Width = end.X - start.X; } else { newRectangle.SetValue(Canvas.LeftProperty, end.X); newRectangle.Width = start.X - end.X; } if (end.Y >= start.Y) { // Defines the top part of the rectangle newRectangle.SetValue(Canvas.TopProperty, start.Y - 50); newRectangle.Height = end.Y - start.Y; } else { newRectangle.SetValue(Canvas.TopProperty, end.Y - 50); newRectangle.Height = start.Y - end.Y; } MyCanvas.Children.Add(newRectangle); } } } |
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