Why not more designer code

Windows Forms Designer error page

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If the Windows Forms Designer cannot be loaded due to an error in the code, in a third-party component, or in another location, an error page is displayed instead of the designer. This error page does not necessarily indicate a bug in the designer. The error could be on the code behind page named . Designer.cs. Errors are displayed in redusible yellow bars with a link to jump to the location of the error on the code page.

You can ignore the errors and continue loading the designer by clicking ignore and continue click. This action can lead to unexpected behavior, such as: b. controls may not appear on the design surface.

Instances of this error

When the yellow error bar is expanded, each instance of the error is listed. Many types of errors contain an exact location in the following format: [Project name][Form name] Row:[Line number] Column:[Column number]. If there is a call stack associated with the error, you can click the link to the View the phone Click the link to display it. Examining the call stacks can help troubleshoot the problem further.

Note

  • For Visual Basic apps, the Design-Time Errors page does not show more than one error, but you may see multiple instances of the same error.
  • For C ++ apps, errors have no code location shortcuts.

Help with this bug

If a help topic is available for the error, click the link MSDN Help to navigate directly to the help page on docs.Microsoft.com.

Forum posts about this bug

Click on the link Search the MSDN forums for posts related to this error to navigate to the Microsoft Developer Network forums. You may want to search the Windows Forms Designer or Windows Forms forums in more detail.

Design timing error

This section lists some of the errors you may encounter.

"" is not a valid identifier.

This error indicates that a field, method, event, or object is not properly named.

"" already exists in "".

Error message: "'" already exists in "" . Enter a unique name. "

You have specified a name for an inherited form that already exists in the project. To fix this error, you need to give the inherited form a unique name.

"" is not a toolbox category.

A third-party designer tried to access a tab in the toolbox that does not exist. Contact the component manufacturer.

A required language parser has not been installed

Error message: "A requested language parser is not installed. The name of the language parser is" {0} ".

Visual Studio tried to load a designer that is registered for the file type, but it cannot. This is likely because an error occurred during setup. Contact the manufacturer of the language you are using to proofread.

A service required to generate and process the source code does not exist

This is a problem with a third party component. Contact the component manufacturer.

Exception when creating an instance of "".

Error message: "An exception occurred while trying to create an instance of '' . Exception :" ".

A third-party designer requested that Visual Studio create an object, but the object threw an error. Contact the component manufacturer.

Another editor opened "" in an incompatible mode.

Error message: "'' is open in an incompatible mode in another editor. Close the editor and try again."

This error occurs when you try to open a file that is already open in another editor. The editor for which the file is already open is displayed. To fix this error, close the editor with the file open and try again.

Another editor made changes to "".

Close and reopen the designer for the changes to take effect. Typically, Visual Studio automatically reloads a designer after making changes. Other designers, such as b. Third-party component designers, however, may not support the reload behavior. In this case, Visual Studio will prompt you to manually close and reopen the designer.

The file is open in an incompatible mode in another editor

Error message: "Another editor is opening the file in an incompatible mode. Close the editor and try again."

This message is similar to "Another editor is open '' in an incompatible mode", but Visual Studio cannot determine the file name. To fix this error, close the editor with the file open and try again.

The array rank "" is too high.

Visual Studio only supports single dimension arrays in the block of code that is being parsed by the designer. Multidimensional arrays are valid outside of this range.

The assembly "" could not be opened.

Error message: "Assembly" could not be opened. Make sure the file still exists. "

This error message appears when you try to open a file that could not be opened. Make sure the file exists and is a valid assembly.

Invalid element type. This serialization program expects an element of the type "".

This is a problem with a third party component. Contact the component manufacturer.

The Visual Studio Toolbox is currently inaccessible

Visual Studio called a toolbox to be called that was not available. If you see this error, when you see this error, use "Report a problem" to log on.

An event handler cannot be bound to the event "" because it is read-only.

This error is most common when you've tried to wire an event to a control that was inherited from a base class. If the control's member variable is private, Visual Studio cannot connect the event to the method. Additional events cannot be bound to private inherited controls.

A method name cannot be created for the requested component because it is not a member of the design container

Visual Studio tried to add an event handler to a component that does not have a member variable in the designer. Contact the component manufacturer.

The name of the object '' cannot be named, because it is already called ''.

This is an internal bug in the Visual Studio serializer. Indicates that the serializer tried to name an object twice, which is unsupported. If you see this error, sign in with "Report a problem".

Inherited component "" cannot be removed or destroyed.

Inherited controls are owned by their inheriting class. Changes to the inherited control must be made in the class from which the control originated. Therefore, you cannot rename it or destroy it.

The category '' has no tool for the class.

The designer tried to reference a class on a specific Toolbox tab, but the class does not exist. Contact the component manufacturer.

The class '' does not have a suitable constructor.

A third-party designer asked Visual Studio to create an object with certain parameters in the constructor that doesn't exist. Contact the component manufacturer.

Error generating code for property "".

This is a generic wrapper for a bug. The error string that accompanies this message provides more details about the error message and a link to a more specific help topic. Fix this error by fixing the error indicated in the error message.

The component "" did not call "Container. Add ()" in the constructor.

This is a bug in the component that you just loaded or placed on the form. Indicates that the component did not add itself to the control container (whether it is another control or a form). The designer is still functional, but you may experience problems with the component at runtime.

Contact the component manufacturer to resolve the problem. Or, if it is a component that you have created, you must call the method in the component's constructor.

The component name cannot be empty

This error occurs when you try to rename a component to an empty value.

The variable "" could not be accessed, because it has not yet been initialized.

This error can occur due to two scenarios. The third party vendor has a problem with a control or component that you distributed, or the code written has recursive dependencies between components.

Make sure the code does not have a recursive dependency to resolve this error. If not, write down the exact text of the error message and contact the component manufacturer.

The type "" was not found.

Error message: "The type" was not found . Make sure the assembly containing this type is referenced. If this type is part of the development project, make sure the project was built successfully . "

This error occurred because no reference was found. Make sure that the type listed in the error message is referenced and that any assemblies that the type requires are also referenced. Often the problem is that a control was not created in the solution. To create, select from the menu Create the Solution option Create out. If the control has already been created, add a reference manually from the context menu of the folder References "or" Dependencies "in Solution Explorer.

The type "" could not be loaded.

Error message: "The type '' could not be loaded . Make sure that the assembly containing this type is added to the project reference."

Visual Studio tried to link a method for event handling and one or more parameter types for the method could not be found. This is usually caused by a missing reference. To fix this error, add the reference with the type to the project and try again.

The project item templates for inherited components could not be found

The templates for inherited forms in Visual Studio are not available. If you see this error, sign in with "Report a problem".

The delegate class "" has no call method. Is this class a delegate.

Visual Studio tried to create an event handler, but there is a problem with the event type. This can happen if the event was created by a non-CLS compliant language. Contact the component manufacturer.

Duplicate declaration of the member ""

This error occurs because a member variable has been declared twice (e.g. two controls with the same name are declared in code). Names must be unique across inherited forms. In addition, names can only differ in upper and lower case

Error reading the resources from the resource file for the culture "".

This error can occur if there is an invalid RESX file in the project.

You can fix this error as follows:

  1. In Solution Explorer, click the button show all files to display the RESX files assigned to the solution.
  2. Load the RESX file in the XML editor by right-clicking the RESX file and to open choose.
  3. Manually edit the .resx file to resolve the errors.

Error reading the resources from the resource file for the standard culture "".

This error can occur if there is an invalid .resx file for the standard culture in the project.

You can fix this error as follows:

  1. In Solution Explorer, click the button show all files to display the RESX files assigned to the solution.
  2. Load the RESX file in the XML editor by right-clicking the RESX file and to open choose.
  3. Manually edit the .resx file to resolve the errors.

The method "" could not be analyzed.

Error message: "The method" "could not be parsed . The parser reported the following error:" ". Check the task list for possible errors."

This is a common error message for problems encountered during processing. These errors are often due to syntax errors. For information about specific messages related to the error, see the task list.

Invalid component name: ""

You tried to rename a component to an invalid value for this language. To resolve this issue, name the component so that it follows the naming rules for that language.

The type "" consists of several partial classes in the same file.

If you define a class in multiple files with the partial keyword, you can only have one partial definition in each file.

To resolve this error, remove all but one of the partial definitions of the class from the file.

The assembly "" could not be found.

Error message: "The assembly '' could not be found. Make sure the assembly is referenced. If the assembly is part of the current development project, make sure the project has been built."

This error is similar to "The type '' was not found", but this error usually occurs because of a metadata attribute. Check that all assemblies used by attributes are referenced to resolve this error.

The assembly name "" is not valid.

A component requested a specific assembly, but the name supplied by the component is not a valid AssemblyName. Contact the component manufacturer.

The base class "" cannot be designed.

The class was loaded by Visual Studio, but the class cannot be designed because the implementer of the class did not provide a designer. If the class supports a designer, make sure that there are no issues that would cause problems when viewing in a designer, such as: b. Compiler error. Also, make sure that all references to the class are correct and that all class names are spelled correctly. If the class isn't design-ready, edit it in Code View.

The base class '' could not be loaded.

The class is not referenced in the project, so Visual Studio cannot load it. To resolve this error, add a reference to the class in the project, and then close and reopen the Windows Forms Designer window.

The class cannot be designed in this version of Visual Studio.

The designer for this control or component does not support the same types as Visual Studio. Contact the component manufacturer.

The class name is not a valid identifier for this language

The source code that is created by the user has a class name that is invalid for the language used. To resolve this issue, rename the class according to the language requirements.

The component cannot be added because it contains a compass reference to "".

You cannot add a control or component yourself.Another situation in which this can occur is if there is code in the InitializeComponent method of a form (such as Form1) that creates another instance of Form1.

The designer cannot be changed at this time

This error occurs when the file is marked as read-only in the editor. Make sure the file is not marked as read-only and the application is not running.

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

This error occurs when Visual Studio cannot find a base class that meets the designer requirements. Forms and controls must derive from a base class that Designer supports. If you're deriving from an inherited form or control, make sure the project was built.

The designer for the base class "" is not installed.

Visual Studio could not load the designer for the class. If you see this error, sign in with "Report a problem".

The designer has to create an instance of the type "", but this is not possible because the type is declared as abstract.

This error occurred because the base class of the object being passed to the designer is abstract, which is not allowed.

The file could not be loaded into the designer

The base class of this file does not support designers. To work around this problem, use Code View to work on the file. Right-click the file in Solution Explorer and select Show code out.

The language for this file does not support the required code processing and generation services.

Error message: "The language for this file does not support the required code and generation services. Make sure the file you are opening is a member of a project and then try to open the file again."

This error is likely due to opening a file that is in a project that does not support designers.

The language parser class "" is not implemented correctly.

Error message: "The language parser class '' is not implemented correctly. Please contact the manufacturer for an updated parser module."

The language used registered a designer class that is not derived from the correct base class. Contact the manufacturer of the language you are using.

The name "" is already in use by another object.

This is an internal bug in the Visual Studio serializer. If you see this error, sign in with "Report a problem".

The object does not implement the IComponent interface.

Visual Studio tried to create a component, but the created object does not implement the IComponent interface. Contact the component manufacturer for a correction.

The object '' returned NULL for the property, but is not allowed.

Some .NET properties should always return an object. For example, the Controls - Collection of a form always return an object, even if there are no controls in it.

To resolve this error, ensure that the property specified in the error is not null.

The serialization data object is of the wrong type

A data object offered by the serializer is not an instance of a type that matches the current serializer that is being used. Contact the component manufacturer.

The service "" is required but could not be found.

Error message: "The service '' is required but could not be found. There may be a problem with your Visual Studio installation."

A service required by Visual Studio is not available. If you want to load a project that the designer does not support, use the code editor to make the necessary changes. If you see this error, sign in with "Report a problem".

The service instance must be derived from or implemented from.

This error indicates that a component or component designer is using the AddService Method that requires an interface and an object, but the specified object does not implement the specified interface. Contact the component manufacturer.

The text in the code editor could not be changed

Error message: "The text in the code window could not be changed. Check that the file is not write-protected and that there is enough space."

This error occurs when Visual Studio cannot edit a file due to disk space or memory problems, or when the file is marked as read-only.

The Toolbox enumeration object only supports querying one item at a time

If you see this error, when you see this error, use "Report a problem" to log on.

The Toolbox item for "" could not be retrieved from the Toolbox.

Error message: "The toolbox element for '' could not be retrieved from the toolbox. Make sure that the assembly containing the toolbox element is properly installed. The toolbox element raised the following error: . "

The component in question threw an exception when it was accessed by Visual Studio. Contact the component manufacturer.

The Toolbox item for "" could not be retrieved from the Toolbox.

Error message: "The Toolbox item for '' could not be obtained from the Toolbox. Please remove the item from the Toolbox and add it again."

This error occurs when the data within the Toolbox element has become corrupted or the version of the component has changed. Remove the item from the Toolbox and add it back.

The type "" could not be found.

Error message: "The type" " was not found. Make sure the assembly is referenced with the type. If the assembly is part of the current development project, make sure the project has been built."

Visual Studio could not find a type when loading the designer. Make sure the assembly is referenced with the type. If the assembly is part of the current development project, make sure that the project has been built.

The type resolution service can only be called by the main application thread

Visual Studio tried to access the required resources from the wrong thread. This error appears when the code that was used to create the designer called the type resolution service from a thread other than the main application thread. To fix this error, you need to get the service from the correct thread or contact the component manufacturer.

The variable "" is either not declared or has never been assigned.

The source code contains a reference to a variable, e.g. b. Button1that is not declared or assigned. If the variable has not been assigned, this message is displayed as a warning, not an error.

There is already a command handler for the menu command "".

This error occurs when a third-party designer adds a command that already has a handler for the command table. Contact the component manufacturer.

A component with the name "" already exists.

Error message: "A component with the name '' already exists. Components must have unique names and names are case-insensitive. A name cannot match the name of a component in a inherited class conflict. "

This error message appears when the name of a component has been changed in the Properties window. To resolve this issue, make sure that all component names are unique, case-insensitive, and do not conflict with the names of components in the inherited classes.

A Toolbox element creator is already registered for the format "".

A third-party component recalled an item on a Toolbox tab, but the item already contained a recall. Contact the component manufacturer.

A code model that is loaded into a designer is not supported by this language engine

This message is similar to the "The language for this file does not support the required coding and generation services" message, but this message contains an internal registration problem. If you see this error, when you see this error, use "Report a problem" to log on.

The type "" does not have a constructor with parameters of the type "".

Visual Studio could not find a constructor that contained parameters that match. This can be the result of providing a constructor with types other than the required types. A point constructor can e.g. b. assume two whole numbers. If you specified floating point numbers, this error will be raised.

To resolve this error, use a different constructor or explicitly cast the parameter types to be the same as the types provided by the constructor.

The reference "" cannot be added to of the current application.

Error message: "The reference '' could not be added to in the current application. Check that another version of '' is not already referenced.

Visual Studio cannot add a reference. To resolve this error, check that a different version of the reference is not already being referenced.

The current file could not be checked out

Error message: "The current file cannot be checked out. The file may be locked or you may need to check out the file manually."

This error occurs when you change a currently checked-in file in source code control. Typically, Visual Studio displays the file check out dialog box so the user can check out the file. This time the file was not checked out, possibly due to a merge conflict during check out. Make sure the file is unlocked, then try manually checking out the file to resolve this error.

The page named "" was not found.

This error occurs when a component designer requests access to a page through the Options dialog box using a name that does not exist. Contact the component manufacturer.

The property "" was not found on the page "".

This error occurs when a component designer requests access to a specific value on a page in the Options dialog box, but that value does not exist. Contact the component manufacturer.

Visual Studio cannot open designers on the file because the class within the file does not inherit from a class that can be edited with a designer

The class was loaded by Visual Studio, but the designer for this class could not be loaded. Visual Studio requires designers to use the first class in a file. Move the class code so that it is the first class in the file, and then reload the designer to fix this error.

Visual Studio cannot save or load instances of type "".

This is a problem with a third party component. Contact the component manufacturer.

Visual Studio cannot open "" in Design View.

Error message: "Visual Studio cannot open '" in Design View. No parser is installed for the file type. "

This error indicates that the project language does not support designer and when trying to open a file in the File Open dialog box or in Solution Explorer. Instead, edit the file in Code View.

Visual Studio could not find a designer for classes of type ""

The class was loaded by Visual Studio, but the class cannot be designed. Instead, edit the class in Code View by right-clicking the class and Show code choose.

See also