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Windows Forms Designer Error Messages
'<identifier name>' is not a valid identifier
'<name>' already exists in '<project name>'
'<Toolbox tab name>' is not a toolbox category
A requested language parser is not installed
A service required for generating and parsing source code is missing
An exception occurred while trying to create an instance of '<object name>'
Another editor has '<document name>' open in an incompatible mode
Another editor has made changes to '<document name>'
Another editor has the file open in an incompatible mode
Array rank '<rank in array>' is too high
Assembly '<assembly name>' could not be opened
Bad element type. This serializer expects an element of type '<type name>'.
Cannot access the Visual Studio Toolbox at this time
Cannot bind an event handler to the '<event name>' event because it is read-only
Cannot create a method name for the requested component because it is not a member of the design container
Cannot name the object '<name>' because it is already named '<name>'
Cannot remove or destroy inherited component '<component name>'
Category '<Toolbox tab name>' does not have a tool for class '<class name>'
Class '<class name>' has no matching constructor
Code generation for property '<property name>' failed
Component '<component name>' did not call Container.Add() in its constructor
Component name cannot be empty
Could not access the variable '<variable name>' because it has not been initialized yet
Could not find type '<type name>'
Could not load type '<type name>'
Could not locate the project item templates for inherited components
Delegate class '<class name>' has no invoke method. Is this class a delegate?
Duplicate declaration of member '<member name>'
Error reading resources from the resource file for the culture '<culture name>'
Error reading resources from the resource file for the default culture '<culture name>'
Failed to parse method '<method name>'
Invalid component name: '<component name>'
The type '<class name>' is made of several partial classes in the same file
The assembly '<assembly name>' could not be found
The assembly name '<assembly name>' is invalid
The base class '<class name>' cannot be designed
The base class '<class name>' could not be loaded
The class '<class name>' cannot be designed in this version of Visual Studio
The class name is not a valid identifier for this language
The component cannot be added because it contains a circular reference to '<reference name>'
The designer cannot be modified at this time
The designer could not be shown for this file because none of the classes within it can be designed
The designer for base class '<class name>' is not installed
The designer inspected the following classes in the file:
The designer must create an instance of type '<type name>', but it can't because the type is declared as abstract
The file could not be loaded in the designer
The following exception has occurred:
The language for this file does not support the necessary code parsing and generation services
The language parser class '<class name>' is not implemented properly
The name '<name>' is already used by another object
The object '<object name>' does not implement the IComponent interface
The object '<object name>' returned null for the property '<property name>' but this is not allowed
The serialization data object is not of the proper type
The service '<service name>' is required, but could not be located
The service instance must derive from or implement '<interface name>'
The text in the code window could not be modified
The Toolbox enumerator object only supports retrieving one item at a time
The Toolbox item for '<component name>' could not be retrieved from the Toolbox
The Toolbox item for '<Toolbox item name>' could not be retrieved from the Toolbox
The type '<type name>' could not be found
The type '<type name>' has no event named '<event name>'
The type '<type name>' has no field named '<field name>'
The type '<type name>' has no property named '<property name>'
The type resolution service may only be called from the main application thread
The variable '<variable name>' is either undeclared or was never assigned
There is already a command handler for the menu command '<menu command name>'
There is already a component named '<component name>'
There is already a Toolbox item creator registered for the format '<format name>'
This language engine does not support a CodeModel with which to load a designer
Type '<type name>' does not have a constructor with parameters of types '<parameter type names>'
Unable to add reference '<reference name>' to the current application
Unable to check out the current file
Unable to find page named '<Options dialog box tab name>'
Unable to find property '<property name>' on page '<Options dialog box tab name>'
Unable to load assembly '<assembly name>'
Visual Studio cannot open a designer for the file because the class within it does not inherit from a class that can be visually designed
Visual Studio cannot save or load instances of the type '<type name>'
Visual Studio is unable to open '<document name>' in Design view
Visual Studio was unable to find a designer for classes of type '<type name>'
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There is already a command handler for the menu command '<menu command name>'

.NET Framework 4.5

This error arises if a third-party designer adds to the command table a command that already has a handler.

To correct this error

  • Note the exact text of the error message and contact the component vendor.

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