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Walkthrough: Validating Data in the Windows Forms DataGridView Control

When you display data entry functionality to users, you frequently have to validate the data entered into your form. The DataGridView class provides a convenient way to perform validation before data is committed to the data store. You can validate data by handling the CellValidating event, which is raised by the DataGridView when the current cell changes.

In this walkthrough, you will retrieve rows from the Customers table in the Northwind sample database and display them in a DataGridView control. When a user edits a cell in the CompanyName column and tries to leave the cell, the CellValidating event handler will examine new company name string to make sure it is not empty; if the new value is an empty string, the DataGridView will prevent the user's cursor from leaving the cell until a non-empty string is entered.

To copy the code in this topic as a single listing, see How to: Validate Data in the Windows Forms DataGridView Control.

In order to complete this walkthrough, you will need:

  • Access to a server that has the Northwind SQL Server sample database.

To validate data entered in a DataGridView

  1. Create a class that derives from Form and contains a DataGridView control and a BindingSource component.

    The following code example provides basic initialization and includes a Main method.

    No code example is currently available or this language may not be supported.
  2. Implement a method in your form's class definition for handling the details of connecting to the database.

    This code example uses a GetData method that returns a populated DataTable object. Be sure that you set the connectionString variable to a value that is appropriate for your database.

    Security noteSecurity Note:

    Storing sensitive information, such as a password, within the connection string can affect the security of your application. Using Windows Authentication, also known as integrated security, is a more secure way to control access to a database. For more information, see Protecting Connection Information (ADO.NET).

    No code example is currently available or this language may not be supported.
  3. Implement a handler for your form's Load event that initializes the DataGridView and BindingSource and sets up the data binding.

    No code example is currently available or this language may not be supported.
  4. Implement handlers for the DataGridView control's CellValidating and CellEndEdit events.

    The CellValidating event handler is where you determine whether the value of a cell in the CompanyName column is empty. If the cell value fails validation, set the Cancel property of the System.Windows.Forms::DataGridViewCellValidatingEventArgs class to true. This causes the DataGridView control to prevent the cursor from leaving the cell. Set the ErrorText property on the row to an explanatory string. This displays an error icon with a ToolTip that contains the error text. In the CellEndEdit event handler, set the ErrorText property on the row to the empty string. The CellEndEdit event occurs only when the cell exits edit mode, which it cannot do if it fails validation.

    No code example is currently available or this language may not be supported.

You can now test the form to make sure it behaves as expected.

To test the form

  • Compile and run the application.

    You will see a DataGridView filled with data from the Customers table. When you double-click a cell in the CompanyName column, you can edit the value. If you delete all the characters and hit the TAB key to exit the cell, the DataGridView prevents you from exiting. When you type a non-empty string into the cell, the DataGridView control lets you exit the cell.

This application gives you a basic understanding of the DataGridView control's capabilities. You can customize the appearance and behavior of the DataGridView control in several ways:

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