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It's time to eradicate VB6
8 Proven Tips for
Planning a Successful Migration
Other enhancements are related to library members that were previously converted to the .NET Visual Basic 6 Compatibility Library. The VBUC converts them to .NET Framework native libraries, as shown in the following table:
| Source pattern | Target .NET pattern |
| <timer_reference>.Interval compared to 0 patterns. | Patterns of <timer_reference>.Enabled |
| Dir(<path>, vbDirectory) compared to empty string. | [!] System.IO.Directory.Exists(<filename>) |
| vb.App.LogEvent | System.Diagnostics.EventLog.WriteEntry |
| VBA.FileSystem.Kill | System.IO.File.Delete |
| vba.FileSystem.FileCopy | System.IO.File.Copy |
| VBA.Strings.Format VBA.Strings.FormatNumber VBA.Strings.FormatPercent |
Different patterns of p.ToString(...) |
| VBA.DateTime.Date | Uses of System.DateTime.Now |
| VBA.DateTime.DateValue | Uses of System.DateTime.Parse |
| VBA.DateTime.DateAdd (<interval>,<num>,<date>) |
<date>.AddYears(<num>) <date>.AddMonths(<num>) <date>.AddDays(<num>) <date>.AddHours(<num>) <date>.AddMinutes(<num>) <date>.AddSeconds(<num>) |
| VBA.Information.IsEmpty(p) where “p” can be a: - numeric - boolean - date - string - object |
numeric -> p.Equals(0) boolean -> p.Equals(false) date -> p.Equals(DateTime.FromOADate(0)) string -> p.IsNullOrEmpty() object -> p.Equals(param,Nothing) |
| VBA.Strings.Split(...) | Various patterns of <string-object>.Split(…) |
| VBA.VbMsgBoxResult | Patterns of System.Windows.Forms.DialogResult |
| VBA.VbDayOfWeek | System.FirstDayOfWeek |
| VBA.Strings.Left VBA.Strings.Right VBA.Strings.Mid |
Uses of <str-object>.Substring(…) |
| VBA.Constants.<char-const> | Strings.Chr(<value>) / chr(13) |
| File IO operations | Converted using System.IO namespace |
If-ElseIf Block to Switch Block
The VBUC detects If-ElseIf blocks with all its conditions, comparing the same expression against different values and converting them to a more natural Switch block.
Replacement of “for” Loops by “foreach” Loops
When VB6 For loops iterate over collections and some arrays, VBUC upgrades the statement to .NET ForEach statements, applying the necessary transformations to the collection/array references inside the For body and the counter variables.
Counter variables that are no longer needed after the Foreach transformation are removed from the resulting code block.
Unify Code Blocks
Some classes in VB6 have two events that correspond to one unique event in the corresponding .NET class. In those cases, the bodies of the two events are merged to achieve the same behavior.
Some examples of these transformations are:
- MSComctlLib.StatusBar PanelClick and PanelDblClick events
- MSComctlLib.ListView ItemClick and Click events
New Objects Declaration
This rule allows adding the variable initialization value to its declaration:
[VB6]
Dim _myvar as MyType ... <Code which doesn’t reference _myvar> _myvar = InitValue
[C#]
MyType _myvar = InitValue; ... <Code which doesn’t reference _myvar>
Automatic “import” Clause Generation
Besides the option of generating references to the .NET library elements by using their fully qualified names, the VBUC introduces an additional transformation stage that recognizes fully qualified names and simplifies them while automatically generating the necessary import / using causes.
This new feature makes the converted code look much better providing an improved readability and maintainability.