Практическое руководство. Отображение значков ошибок при проверке введенных в форму данных с помощью компонента ErrorProvider в Windows Forms How to: Display Error Icons for Form Validation with the Windows Forms ErrorProvider Component

Можно использовать ErrorProvider компонент Windows Forms для вывода значка ошибки при вводе пользователем недопустимых данных. You can use a Windows Forms ErrorProvider component to display an error icon when the user enters invalid data. Необходимо иметь по крайней мере два элемента управления в форме, чтобы они могли переходить между ними и таким образом вызывать код проверки. You must have at least two controls on the form in order to tab between them and thereby invoke the validation code.

Отображение значка ошибки при недопустимом значении элемента управления To display an error icon when a control’s value is invalid

Добавьте два элемента управления, например текстовые поля, в форму Windows. Add two controls — for example, text boxes — to a Windows Form.

Добавьте ErrorProvider компонент в форму. Add an ErrorProvider component to the form.

Выберите первый элемент управления и добавьте код в его Validating обработчик событий. Select the first control and add code to its Validating event handler. Чтобы этот код выполнялся должным образом, процедура должна быть подключена к событию. In order for this code to run properly, the procedure must be connected to the event. Дополнительные сведения см. в разделе инструкции. Создание обработчиков событий во время выполнения для Windows Forms. For more information, see How to: Create Event Handlers at Run Time for Windows Forms.

Следующий код проверяет допустимость вводимых пользователем данных. Если данные недопустимы, SetError вызывается метод. The following code tests the validity of the data the user has entered; if the data is invalid, the SetError method is called. Первый аргумент SetError метода указывает, какой элемент управления должен отображать значок рядом с. The first argument of the SetError method specifies which control to display the icon next to. Вторым аргументом является отображаемый текст ошибки. The second argument is the error text to display.

(Visual C#, Visual C++) Поместите следующий код в конструктор формы для регистрации обработчика событий. (Visual C#, Visual C++) Place the following code in the form’s constructor to register the event handler.

Запустите проект. Run the project. Недопустимый тип (в этом примере нечисловые) данные в первом элементе управления, а затем на вкладку Second. Type invalid (in this example, non-numeric) data into the first control, and then tab to the second. Когда отображается значок ошибки, наведите указатель мыши на него, чтобы увидеть текст ошибки. When the error icon is displayed, point at it with the mouse pointer to see the error text.

Вывести окно с ошибкой при вводе пользователем некорректного выражения

Вывод ошибки при вводе некорректного значения в MaskedTextBox
Здравствуйте, у меня вопрос по поводу события Validating: у меня есть на форме maskedTextBox1, у.

Поведение cin при вводе некорректного типа данных
Был создан цикл: while (err) //bool err = true < try < cin >> arrsz // int.

При вводе пользователем числа от 0 до 9, вывести на экран название программы (использовать оператор goto)
Программу по заданию я написал Написать программу для выполнения следующих действий. При вводе.

Решение

Заказываю контрольные, курсовые, дипломные и любые другие студенческие работы здесь или здесь.

Вывести окно с ошибкой
Надо сделать, чтобы выводило окно ошибки (аварийный ответ), когда введенное значение меньше нуля.

Вывести на экран окно с ошибкой во время компиляции
Добрый вечер. Начал изучать Turbo Pascal 7.0, возник вопрос, как вывести на экран окно с ошибкой.

Рассчитать и вывести значения выражения,при заданных пользователем значения x и a
Рассчитать и вывести значения выражения,при заданных пользователем значения x и a. .

Выпадающий список при вводе текста пользователем в форму
Всем привет! Сделал скрипт, который ищет значения из БД. Скрипт написан на php. хочу сделать.

Практическое руководство. Обработка ошибок и исключений, происходящих при связывании элементов управления с данными How to: Handle Errors and Exceptions that Occur with Databinding

Зачастую при привязке базовых бизнес-объектов к элементам управления возникают ошибки и исключения. Oftentimes exceptions and errors occur on the underlying business objects when you bind them to controls. Эти ошибки и исключения можно перехватывать, а затем исправлять или передавать сведения об ошибке пользователю путем обработки события BindingComplete для конкретного компонента Binding, BindingSource или CurrencyManager. You can intercept these errors and exceptions and then either recover or pass the error information to the user by handling the BindingComplete event for a particular Binding, BindingSource, or CurrencyManager component.

Пример Example

В данном примере кода показан способ обработки ошибок и исключений, возникающих при выполнении операции привязки данных. This code example demonstrates how to handle errors and exceptions that occur during a data-binding operation. Он демонстрирует перехват ошибок путем обработки события Binding.BindingComplete объектов Binding. It demonstrates how to intercept errors by handling the Binding.BindingComplete event of the Binding objects. Для перехвата ошибок и исключений с помощью обработки этого события необходимо включить поддержку форматирования для привязки. In order to intercept errors and exceptions by handling this event, you must enable formatting for the binding. Форматирование можно включить при создании привязки или добавлении в коллекцию привязок, или установив значение свойства FormattingEnabled равным true . You can enable formatting when the binding is constructed or added to the binding collection, or by setting the FormattingEnabled property to true .

Во время выполнения, если введена пустая строка в качестве имени или значение меньше 100 в качестве числа, то появится окно с сообщением. When the code is running and an empty string is entered for the part name or a value less than 100 is entered for the part number, a message box appears. Это происходит в результате обработки события Binding.BindingComplete для привязок этих текстовых полей. This is a result of handling the Binding.BindingComplete event for these textbox bindings.

Компиляция кода Compiling the Code

Для этого примера требуются: This example requires:

Windows Forms Designer error page

If the Windows Forms Designer fails to load due to an error in your code, in a third-party component, or elsewhere, you’ll see an error page instead of the designer. This error page does not necessarily signify a bug in the designer. The bug may be somewhere in the code-behind page that’s named .Designer.cs. Errors appear in collapsible, yellow bars with a link to jump to the location of the error on the code page.

You can choose to ignore the errors and continue loading the designer by clicking Ignore and Continue. This action may result in unexpected behavior, for example, 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 error types include an exact location in the following format: [Project Name] [Form Name] Line:[Line Number] Column:[Column Number]. If a call stack is associated with the error, you can click the Show Call Stack link to see it. Examining the call stack may further help you resolve the error.

• For Visual Basic apps, the design-time error page does not display more than one error, but it may display multiple instances of the same error.
• For C++ apps, errors don’t have code location links.

Help with this error

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

Forum posts about this error

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

Design-time errors

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 improperly named.

‘ ‘ already exists in ‘

Error message: «‘ ‘ already exists in ‘

‘. Please enter a unique name.»

You’ve specified a name for an inherited form that already exists in the project. To correct this error, give the inherited form a unique name.

‘ ‘ is not a toolbox category

A third-party designer has tried to access a tab on the Toolbox that does not exist. Contact the component vendor.

A requested language parser is not installed

Error message: «A requested language parser is not installed. The language parser name is ‘<0>‘.»

Visual Studio attempted to a load a designer that’s registered for the file type but could not. This is most likely because of an error that occurred during setup. Contact the vendor of the language you’re using for a fix.

A service required for generating and parsing source code is missing

This is a problem with a third-party component. Contact the component vendor.

An exception occurred while trying to create an instance of ‘ ‘

Error message: «An exception occurred while trying to create an instance of ‘ ‘. The exception was » «.

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

Another editor has ‘ ‘ open in an incompatible mode

Error message: «Another editor has ‘ ‘ open in an incompatible mode. Please close the editor and try this operation again.»

This error arises if you try to open a file that is already opened in another editor. The editor that already has the file open is shown. To correct this error, close the editor that has the file open, and try again.

Another editor has made changes to ‘ ‘

Close and reopen the designer for the changes to take effect. Normally, Visual Studio automatically reloads a designer after changes are made. However, other designers, such as third-party component designers, may not support reload behavior. In this case, Visual Studio prompts you to close and reopen the designer manually.

Another editor has the file open in an incompatible mode

Error message: «Another editor has the file open in an incompatible mode. Please close the editor and try this operation again.»

This message is similar to «Another editor has ‘ ‘ open in an incompatible mode», but Visual Studio is unable to determine the file name. To correct this error, close the editor that has the file open, and try again.

Array rank ‘ ‘ is too high

Visual Studio only supports single-dimension arrays in the code block that’s parsed by the designer. Multidimensional arrays are valid outside this area.

Assembly » could not be opened

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

Bad element type. This serializer expects an element of type ‘ ‘

This is a problem with a third-party component. Contact the component vendor.

Cannot access the Visual Studio Toolbox at this time

Visual Studio made a call to the Toolbox, which was not available. If you see this error, If you see this error, please log an issue by using Report a Problem.

Cannot bind an event handler to the ‘ ‘ event because it is read-only

This error most often arises when you’ve tried to connect an event to a control that’s inherited from a base class. If the control’s member variable is private, Visual Studio cannot connect the event to the method. Privately inherited controls cannot have additional events bound to them.

Cannot create a method name for the requested component because it is not a member of the design container

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

Cannot name the object ‘ ‘ because it is already named ‘ ‘

This is an internal error in the Visual Studio serializer. It indicates that the serializer has tried to name an object twice, which is not supported. If you see this error, please log an issue by using Report a Problem.

Cannot remove or destroy inherited component ‘ ‘

Inherited controls are under the ownership of their inheriting class. Changes to the inherited control must be made in the class from which the control originates. Thus, you cannot rename or destroy it.

Category ‘ ‘ does not have a tool for class ‘ ‘

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

Class ‘ ‘ has no matching constructor

A third-party designer has asked Visual Studio to create an object with particular parameters in the constructor that does not exist. Contact the component vendor.

Code generation for property ‘

This is a generic wrapper for an error. The error string that accompanies this message will give more details about the error message and have a link to a more specific help topic. To correct this error, address the error specified in the error message appended to this error.

Component ‘ ‘ did not call Container.Add() in its constructor

This is an error in the component you just loaded or placed on the form. It indicates that the component did not add itself to its container control (whether that is another control or a form). The designer will continue to work, but there may be problems with the component at run time.

To correct the error, contact the component vendor. Or, if it is a component you created, call the IContainer.Add method in the component’s constructor.

Component name cannot be empty

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

Could not access the variable ‘ ‘ because it has not been initialized yet

This error can arise because of two scenarios. Either a third-party component vendor has a problem with a control or component they have distributed, or the code you have written has recursive dependencies between components.

To correct this error, ensure that your code does not have a recursive dependency. If it is free of such problems, note the exact text of the error message and contact the component vendor.

Could not find type ‘ ‘

Error message: «Could not find type ‘ ‘. Please make sure that the assembly that contains this type is referenced. If this type is a part of your development project, make sure that the project has been successfully built.»

This error occurred because a reference was not found. Make sure the type indicated in the error message is referenced, and that any assemblies that the type requires are also referenced. Often, the problem is that a control in the solution has not been built. To build, select Build Solution from the Build menu. Otherwise, if the control has already been built, add a reference manually from the right-click menu of the References or Dependencies folder in Solution Explorer.

Could not load type ‘ ‘

Error message: «Could not load type ‘ ‘. Please make sure that the assembly containing this type is added to the project references.»

Visual Studio attempted to wire up an event-handling method and could not find one or more parameter types for the method. This is usually caused by a missing reference. To correct this error, add the reference containing the type to the project and try again.

Could not locate the project item templates for inherited components

The templates for inherited forms in Visual Studio are not available. If you see this error, please log an issue by using Report a Problem.

Delegate class ‘ ‘ has no invoke method. Is this class a delegate

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

Duplicate declaration of member ‘ ‘

This error arises because a member variable has been declared twice (for example, two controls named Button1 are declared in the code). Names must be unique across inherited forms. Additionally, names cannot differ only by case.

Error reading resources from the resource file for the culture ‘ ‘

This error can occur if there is a bad .resx file in the project.

To correct this error:

1. Click the Show All Files button in Solution Explorer to view the .resx files associated with the solution.
2. Load the .resx file in the XML Editor by right-clicking the .resx file and choosing Open.
3. Edit the .resx file manually to address the errors.

Error reading resources from the resource file for the default culture ‘ ‘

This error can occur if there is a bad .resx file in the project for the default culture.

To correct this error:

1. Click the Show All Files button in Solution Explorer to view the .resx files associated with the solution.
2. Load the .resx file in the XML Editor by right-clicking the .resx file and choosing Open.
3. Edit the .resx file manually to address the errors.

Failed to parse method ‘ ‘

Error message: «Failed to parse method ‘ ‘. The parser reported the following error: ‘ ‘. Please look in the Task List for potential errors.»

This is a general error message for problems that arise during parsing. These errors are often due to syntax errors. See the Task List for specific messages related to the error.

Invalid component name: ‘ ‘

You’ve tried to rename a component to an invalid value for that language. To correct this error, name the component such that it complies with the naming rules for that language.

The type ‘ ‘ is made of several partial classes in the same file

When you define a class in multiple files by using the partial keyword, you can only have one partial definition in each file.

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

The assembly » could not be found

This error is similar to «The type ‘ ‘ could not be found», but this error usually happens because of a metadata attribute. To correct this error, check that all assemblies used by attributes are referenced.

The assembly name » is invalid

A component has requested a particular assembly, but the name provided by the component is not a valid assembly name. Contact the component vendor.

The base class ‘ ‘ cannot be designed

Visual Studio loaded the class, 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 there are no problems that would cause issues with displaying it in a designer, such as compiler errors. Also, make sure that all references to the class are correct and all class names are correctly spelled. Otherwise, if the class is not designable, edit it in Code view.

The base class ‘ ‘ could not be loaded

The class is not referenced in the project, so Visual Studio can’t load it. To correct this error, add a reference to the class in the project, and 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 that Visual Studio does. Contact the component vendor.

The class name is not a valid identifier for this language

The source code being created by the user has a class name that is not valid for the language being used. To correct this error, name the class such that it conforms to the language requirements.

The component cannot be added because it contains a circular reference to ‘ ‘

You cannot add a control or component to itself. Another situation where this might occur is if there is code in the InitializeComponent method of a form (for example, Form1) that creates another instance of Form1.

The designer cannot be modified at this time

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

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

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

The designer for base class ‘ ‘ is not installed

Visual Studio could not load the designer for the class. If you see this error, please log an issue by using Report a Problem.

The designer must create an instance of type ‘ ‘, but it can’t 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 in the designer

The base class of this file does not support any designers. As a workaround, use Code view to work on the file. Right-click the file in Solution Explorer and choose View Code.

The language for this file does not support the necessary code parsing and generation services

Error message: «The language for this file does not support the necessary code parsing and generation services. Please ensure the file you are opening is a member of a project and then try to open the file again.»

This error most likely resulted from opening a file that’s in a project that does not support designers.

The language parser class ‘ ‘ is not implemented properly

Error message: «The language parser class ‘ ‘ is not implemented properly. Contact the vendor for an updated parser module.»

The language in use has registered a designer class that doesn’t derive from the correct base class. Contact the vendor of the language you’re using.

The name ‘ ‘ is already used by another object

This is an internal error in the Visual Studio serializer. If you see this error, please log an issue by using Report a Problem.

The object ‘ ‘ does not implement the IComponent interface

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

The object ‘ ‘ returned null for the property ‘

‘ but this is not allowed

There are some .NET properties that should always return an object. For example, the Controls collection of a form should always return an object, even when there are no controls in it.

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

The serialization data object is not of the proper type

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

The service ‘ ‘ is required, but could not be located

Error message: «The service ‘ ‘ is required, but could not be located. There may be a problem with your Visual Studio installation.»

A service required by Visual Studio is unavailable. If you were trying to load a project that does not support that designer, use the Code Editor to make the changes you require. Otherwise, If you see this error, please log an issue by using Report a Problem.

The service instance must derive from or implement ‘ ‘

This error indicates that a component or component designer has called the AddService method, which requires an interface and object, but the object specified does not implement the interface specified. Contact the component vendor.

The text in the code window could not be modified

Error message: «The text in the code window could not be modified. Check that the file is not read-only and there is sufficient disk space.»

This error occurs when Visual Studio is unable to edit a file due to disk space or memory problems, or the file is marked read-only.

The Toolbox enumerator object only supports retrieving one item at a time

If you see this error, If you see this error, please log an issue by using Report a Problem.

The Toolbox item for ‘ ‘ could not be retrieved from the Toolbox

Error message: «The Toolbox item for ‘ ‘ could not be retrieved from the Toolbox. Make sure the assembly that contains the Toolbox item is correctly installed. The Toolbox item raised the following error: .»

The component in question threw an exception when Visual Studio accessed it. Contact the component vendor.

The Toolbox item for ‘ ‘ could not be retrieved from the Toolbox

Error message: «The Toolbox item for ‘ ‘ could not be retrieved from the Toolbox. Try removing the item from the Toolbox and adding it back.»

This error occurs if the data within the Toolbox item becomes corrupted or the version of the component has changed. Try removing the item from the Toolbox and adding it back again.

The type ‘ ‘ could not be found

Error message: «The type ‘ ‘ could not be found. Ensure that the assembly containing the type is referenced. If the assembly is part of the current development project, ensure that the project has been built.»

While loading the designer, Visual Studio failed to find a type. Ensure that the assembly containing the type is referenced. If the assembly is part of the current development project, ensure that the project has been built.

The type resolution service may only be called from the main application thread

Visual Studio attempted to access required resources from the wrong thread. This error is displayed when the code used to create the designer has called the type resolution service from a thread other than the main application thread. To correct this error, call the service from the correct thread or contact the component vendor.

The variable ‘ ‘ is either undeclared or was never assigned

The source code has a reference to a variable, such as Button1, that isn’t declared or assigned. If the variable has not been assigned, this message appears as a warning, not an error.

There is already a command handler for the menu command ‘ ‘

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

There is already a component named ‘ ‘

Error message: «There is already a component named ‘ ‘. Components must have unique names, and names must not be case-sensitive. A name also cannot conflict with the name of any component in an inherited class.»

This error message arises when there has been a change to the name of a component in the Properties window. To correct this error, ensure that all component names are unique, are not case-sensitive, and do not conflict with the names of any components in the inherited classes.