pdf417 source code c# Custom Rule Methods in visual C#.net

Paint pdf417 in visual C#.net Custom Rule Methods

Figure 7-8 illustrates this set of virtual and override methods. Notice how the behavior differs from the previous case, where I used new to hide the base class members. When the Print method is called by using the reference to the base class (mybc), the method call is passed up to the derived class and executed, because of the following: The method in the base class is marked as virtual. There is a matching override method in the derived class. Figure 7-8 illustrates this by showing the arrow coming out the back of the virtual Print method and pointing at the override Print method.

Summary

Figure 18-5. Attempting to convert a ushort to a byte Clearly, only a relatively small number (0.4 percent) of the possible unsigned 16-bit ushort values can be safely converted to an unsigned 8-bit byte type without loss of data. The rest result in data overflow, yielding different values.

To see further that workflow and activities are code, close the Object Browser and view the code in the workflow file (called Workflow1.vb), as follows: Imports System Imports System.ComponentModel Imports System.ComponentModel.Design Imports System.Collections Imports System.Drawing Imports System.Workflow.ComponentModel.Compiler Imports System.Workflow.ComponentModel.Serialization Imports System.Workflow.ComponentModel Imports System.Workflow.ComponentModel.Design Imports System.Workflow.Runtime Imports System.Workflow.Activities Imports System.Workflow.Activities.Rules Partial Public Class Workflow1 Inherits SequentialWorkflowActivity Public Sub New() MyBase.New() InitializeComponent() End Sub End Class Notice all the Import statements, including the Import statements for the various namespaces within the workflow assemblies that were discussed earlier. Because workflow itself isn t executable and must be hosted, all these namespaces must be imported so the workflow can stand alone. Because this is a Sequential workflow (instead of a State Machine workflow), the class Workflow1 inherits from the SequentialWorkflowActivity class. To get an understanding of where the SequentialWorkflowActivity class fits into all the workflow assemblies, right-click SequentialWorkflowActivity and choose Goto Definition. This opens the Object Browser back up to the SequentialWorkflowActivity class. Notice it s part of the Activities namespace within the Activities assembly. You ll also find the StateMachineWorkflowActivity class within this namespace.

Main can be declared public or private: If Main is declared private, other assemblies cannot access it, and only the execution environment can start the program. If Main is declared public, other assemblies can call it.