Ged Mead
Ged Mead (XTab) is a Microsoft Visual Basic MVP who has been working on computer software and design for more than 25 years. His journey has taken him through many different facets of IT. These include training as a Systems Analyst, working in a mainframe software development environment, creating financial management systems and a short time spent on military laptop systems in the days when it took two strong men to carry a 'mobile' system.
Based in an idyllic lochside location in the West of Scotland, he is currently involved in an ever-widening range of VB.NET, WPF and Silverlight development projects. Now working in a consultancy environment, his passion however still remains helping students and professional developers to take advantage of the ever increasing range of sophisticated tools available to them.
Ged is a regular contributor to forums on vbCity and authors articles for DevCity. He is a moderator on VBCity and the MSDN Tech Forums and spends a lot of time answering technical questions there and in several other VB forum sites. Senior Editor for DevCity.NET, vbCity Developer Community Leader and Admin, and DevCity.NET Newsletter Editor. He has written and continues to tutor a number of free online courses for VB.NET developers.
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Skeleton Layout
Because these articles are aimed at showing you how to use the Graphics Classes, I will skim over most of the non-graphics stuff wherever I can. So, to help shortcut the process of creating the Windows Form and its controls, I have included a project containing a skeleton form (i.e. it contains the controls, but none of the graphics code). You will find it in the folder named "Skeleton" in the attached zip file.
The form and its controls looks like this:
Of course, if you prefer to build the form yourself, go ahead. I will let you know the names used and other details for the controls where these are significant to the code as we come to them.
Let's get Coding
Insert these statements at the top of the form:
Option Strict On
Imports System.Drawing.Drawing2D
Imports System.Collections
As in the previous articles, a Structure is used to compartmentalise the data and an arraylist to store it. It's quick and easy and should be very familiar by now.
Structure GraphData
Dim Name As String
Dim Amount As Decimal
Dim Clr As Color
Dim Pattern As HatchStyle
End Structure
' Arraylist to hold data as it is input by user
Dim UserData As New ArrayList
This Structure is similar to the one created in Part 1 - the first three fields (Name, Amount and Clr) representing the same elements. The additional item (Pattern) will hold the user's choices of HatchStyles.
The framework offers a range of more than 50 HatchStyles - basically, they offer a choice of coloured shadings. The image below shows a few sample styles:
Temporary Variables
From the work we did in Parts 1 and 2, you will know that we will create instances of our User Defined Value Type (GraphData) and assign values to each of the four fields. In this version we will let the user do this at run time.
We also need a couple of variables to hold the values of the Color and HatchStyle elements temporarily while the user is choosing the rest of the settings. Add these to the declarations area where you instantiated the arraylist:
Dim clrPicked As Drawing.Color = Color.Black
Dim hatchPicked As HatchStyle = HatchStyle.DarkHorizontal
You will see that default values (Black and DarkHorizontal) are included in the code above. Doing this avoids errors which would otherwise arise if the user forgets to select either of these elements.