Error message when you compile a WPF application in Visual Basic 2008: "Option Strict On disallows implicit conversions"


You may receive an error message that resembles the following when you try to compile a Windows Presentation Foundation (WPF) application in Microsoft Visual Basic 2008:
Option Strict On disallows implicit conversions from 'System.Windows.Application' to 'WpfApplication1.Application'.


This issue occurs if the value of the Option Strict statement is "On" at the project level.


To resolve this issue, download an updated WPF template. To obtain the updated template, visit the following Microsoft Web site:Important You do not have to unzip the compressed file with a .zip file name extension to install the updated template. To install the updated template, put the .compressed file with a .zip file name extension in the \Visual Studio 2008\Templates\ProjectTemplates\Visual Basic folder, and then restart Visual Studio 2008.

After you install the updated template, the updated template appears in the New Project dialog box in the My Templates section. This section is located under the Visual Studio installed templates section.


To work around this issue in the current project, modify the code in the Mywpfextension.vb file. To modify the code in the Mywpfextension.vb file, follow these steps:
  1. Under Error List, double-click the error message that the "Symptoms" section describes. The Mywpfextension.vb file opens.
  2. Locate the following line of code:
    Return Global.System.Windows.Application.Current
  3. Modify the code in step 2 as follows:
    Return CType(Global.System.Windows.Application.Current, Application)
  4. Build the project again.

More Information

This issue occurs because the code in the WPF template performs an implicit cast. Implicit casts are not allowed when Option Strict checking is turned on.


For more information about the Option Strict statement, visit the following Microsoft MSDN Web site:

文書番号:945756 - 最終更新日: 2007/12/03 - リビジョン: 1