code to generate barcode in vb.net Part II in C#.NET

Printer UPC-A Supplement 2 in C#.NET Part II

Part II
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Scanning UPCA In Visual C#.NET
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Working with Activities
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5. Now we can add the using statements we ll need. Following the list of using statements Visual Studio inserted for you when the source file was created, add these:
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using using using using using using using using using System.IO; System.Net; System.ComponentModel; System.ComponentModel.Design; System.Workflow.ComponentModel; System.Workflow.ComponentModel.Compiler; System.Workflow.ComponentModel.Design; System.Workflow.Activities; System.Drawing;
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6. Because we re building an activity, we need to derive FtpGetFileActivity from the appropriate base class. Change the current class definition to the following:
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public sealed class FtpGetFileActivity : System.Workflow.ComponentModel.Activity
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Note Because you re creating a basic activity, the FTP activity derives from System.Workflow.ComponentModel.Activity. However, if you were creating a composite activity, it would derive from System.Workflow.ComponentModel.CompositeActivity. 7. For this example, the FtpGetFileActivity will expose three properties: FtpUrl, FtpUser, and FtpPassword. Activity properties are nearly always dependency properties, so we ll add three dependency properties, starting with the FtpUrl. Type this code into the FtpGetFileActivity class following the class s opening brace (at this point the class contains no other code):
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public static DependencyProperty FtpUrlProperty = DependencyProperty.Register("FtpUrl", typeof(System.String), typeof(FtpGetFileActivity)); [Description ("Please provide the full URL for the file to download.")] [DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)] [ValidationOption(ValidationOption.Required)] [Browsable(true)] [Category("FTP Parameters")] public string FtpUrl { get { return ((string) (base.GetValue(FtpGetFileActivity.FtpUrlProperty))); } set { Uri tempUri = null; if (Uri.TryCreate(value, UriKind.Absolute, out tempUri)) { if (tempUri.Scheme == Uri.UriSchemeFtp) { base.SetValue(FtpGetFileActivity.FtpUrlProperty,
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13
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tempUri.AbsoluteUri); } } else {
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Crafting Custom Activities
// Not a valid FTP URI... throw new ArgumentException("The value assigned to the" + " FtpUrl property is not a valid FTP URI."); }; } }
Note
It is beyond the scope of this chapter to fully describe all the designer attributes and how they allow the FtpGetFileActivity to be hosted within the visual workflow designer. However, having said that, the Description attribute provides verbal feedback in the Visual Studio Properties pane when the given property is selected. The DesignerSerializationVisibility attribute dictates how the property will be encoded when the designer inserts code. (In this case, the property itself will be encoded.) The Browsable attribute tells Visual Studio to show this property in the editor. And the Category attribute dictates where in the property grid the property will be shown (in this case, a custom category). The ValidationOption attribute is WF-specific and tells the visual workflow designer whether this property s validation is optional or not optional. (In this case, the FTP URL is not optional.) We ll need this attribute later when we add a custom activity validator. http://msdn2.microsoft.com/en-us/library/a19191fh.aspx provides you with an overview of the designer attributes and their use as well as links to even more information.
8. Next add the code for the FtpUser property. Place this code following the FtpUrl code you inserted in the preceding step:
public static DependencyProperty FtpUserProperty = DependencyProperty.Register("FtpUser", typeof(System.String), typeof(FtpGetFileActivity)); [Description("Please provide the FTP user account name.")] [DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)] [ValidationOption(ValidationOption.Optional)] [Browsable(true)] [Category("FTP Parameters")] public string FtpUser { get { return ((string)( base.GetValue(FtpGetFileActivity.FtpUserProperty))); } set { base.SetValue(FtpGetFileActivity.FtpUserProperty, value); } }
Part II
Working with Activities
9. Now place the final property, FtpPassword, following the FtpUser code you just inserted:
public static DependencyProperty FtpPasswordProperty = DependencyProperty.Register("FtpPassword", typeof(System.String), typeof(FtpGetFileActivity)); [Description("Please provide the FTP user account password.")] [DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)] [ValidationOption(ValidationOption.Optional)] [Browsable(true)] [Category("FTP Parameters")] public string FtpPassword { get { return ((string)( base.GetValue(FtpGetFileActivity.FtpPasswordProperty))); } set { base.SetValue(FtpGetFileActivity.FtpPasswordProperty, value); } }
10. As you may know, some FTP servers allow for anonymous access. While many require users to be registered with the server, other FTP sites are configured for public access. In the case of public access, the user name is traditionally anonymous, with the user s email address used as the password (presumably for tracking purposes). We ll require the FtpGetFileActivity to have an FTP URL, but the user name and password will be optional from the application s perspective. However, from an FTP perspective, we have to provide something. Therefore, we ll add these constant strings now for later use when we insert the code for FTP authentication. Therefore, following the FtpPassword property you just inserted, add these constant strings:
private const string AnonymousUser = "anonymous"; private const string AnonymousPassword = "someone@example.com";
11. Depending upon what you want your custom activity to do, you ll typically override one or several of the virtual methods the base Activity class exposes. While it s not strictly required, you ll probably want to at least override Execute because that s where the work will be accomplished. Following the constant strings you inserted into FtpGetFileActivity s source file, add this code to override Execute:
protected override ActivityExecutionStatus Execute( ActivityExecutionContext executionContext) { // Retrieve the file. GetFile(); // Work complete, so close. return ActivityExecutionStatus.Closed; }
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