The file could not be loaded into the Web Forms designer...

Problem

You get this error when opening your application in Visual Studio .NET:

Microsoft Development Environment

The file could not be loaded into the Web Forms designer. Please correct the following error and then try loading it again:

The designer could not be shown for this file because none of the classes within it can be designed.

The error message is reported by because the project was not originally built in Microsoft Visual Studio .NET. The Microsoft Visual Design feature in Visual Studio .NET requires that the code behinds be built using Visual Studio .NET at least once before opening the page in Visual Studio .NET. If you open the VBPROJ or CSPROJ files in Microsoft Visual Studio .NET the first time and try to open one of the ASPX pages, you may get the following error message:

Solution

To fix this problem, build your solution from within Microsoft Visual Studio .NET once before opening any of the ASPX pages.

Follow these steps to make your application compliant with Microsoft Visual Design.

Step 1: Create your application in Iron Speed Designer before opening its ASPX files or project solution files in Visual Studio .NET.

Iron Speed Designer updates your application’s CSPROJ or VBPROJ file each time your application is updated. If you do not first rebuild your application, Visual Studio .NET will not be able to find all of your application’s files.

Step 2: Open your application's project file in Visual Studio .NET, e.g.:

For C#:

C:\MyApp\MyApp.csproj

For Visual Basic .NET:

C:\MyApp\MyApp.vbproj

Step 3: Select Build Solution in the Build menu. This will rebuild the SLN solution file. The environment should then work properly.

Please remember that if you edit the ASPX page in Visual Studio .NET, those edits will be lost when you update your pages in Iron Speed Designer.