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How to: Handle Errors That Occur During Data Entry in the Windows Forms DataGridView Control

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The following code example demonstrates how to use the DataGridView control to report data entry errors to the user.

For a complete explanation of this code example, see Walkthrough: Handling Errors that Occur During Data Entry in the Windows Forms DataGridView Control.

Example

using System;
using System.Data;
using System.Data.SqlClient;
using System.Windows.Forms;

public class Form1 : System.Windows.Forms.Form
{
    private DataGridView dataGridView1 = new DataGridView();
    private BindingSource bindingSource1 = new BindingSource();

    public Form1()
    {
        // Initialize the form.
        this.dataGridView1.Dock = DockStyle.Fill;
        this.Controls.Add(dataGridView1);
        this.Load += new EventHandler(Form1_Load);
    }

    private void Form1_Load(System.Object sender, System.EventArgs e)
    {
        // Attach the DataError event to the corresponding event handler.
        this.dataGridView1.DataError +=
            new DataGridViewDataErrorEventHandler(dataGridView1_DataError);

        // Initialize the BindingSource and bind the DataGridView to it.
        bindingSource1.DataSource = GetData("select * from Customers");
        this.dataGridView1.DataSource = bindingSource1;
        this.dataGridView1.AutoResizeColumns(
            DataGridViewAutoSizeColumnsMode.AllCellsExceptHeader);
    }

    private void dataGridView1_DataError(object sender,
        DataGridViewDataErrorEventArgs e)
    {
        // If the data source raises an exception when a cell value is
        // commited, display an error message.
        if (e.Exception != null &&
            e.Context == DataGridViewDataErrorContexts.Commit)
        {
            MessageBox.Show("CustomerID value must be unique.");
        }
    }

    private static DataTable GetData(string selectCommand)
    {
        string connectionString =
            "Integrated Security=SSPI;Persist Security Info=False;" +
            "Initial Catalog=Northwind;Data Source=localhost;Packet Size=4096";

        // Connect to the database and fill a data table, including the
        // schema information that contains the CustomerID column
        // constraint.
        SqlDataAdapter adapter =
            new SqlDataAdapter(selectCommand, connectionString);
        DataTable data = new DataTable();
        data.Locale = System.Globalization.CultureInfo.InvariantCulture;
        adapter.Fill(data);
        adapter.FillSchema(data, SchemaType.Source);

        return data;
    }

    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.Run(new Form1());
    }
}

Imports System.Data
Imports System.Data.SqlClient
Imports System.Windows.Forms

Public Class Form1
    Inherits System.Windows.Forms.Form

    Private WithEvents dataGridView1 As New DataGridView()
    Private bindingSource1 As New BindingSource()

    Public Sub New()

        ' Initialize the form.
        Me.dataGridView1.Dock = DockStyle.Fill
        Me.Controls.Add(dataGridView1)

    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles Me.Load

        ' Initialize the BindingSource and bind the DataGridView to it.
        bindingSource1.DataSource = GetData("select * from Customers")
        Me.dataGridView1.DataSource = bindingSource1
        Me.dataGridView1.AutoResizeColumns( _
            DataGridViewAutoSizeColumnsMode.AllCellsExceptHeader)

    End Sub

    Private Sub dataGridView1_DataError(ByVal sender As Object, _
        ByVal e As DataGridViewDataErrorEventArgs) _
        Handles dataGridView1.DataError

        ' If the data source raises an exception when a cell value is 
        ' commited, display an error message.
        If e.Exception IsNot Nothing AndAlso _
            e.Context = DataGridViewDataErrorContexts.Commit Then

            MessageBox.Show("CustomerID value must be unique.")

        End If

    End Sub

    Private Shared Function GetData(ByVal selectCommand As String) As DataTable

        Dim connectionString As String = _
            "Integrated Security=SSPI;Persist Security Info=False;" + _
            "Initial Catalog=Northwind;Data Source=localhost;Packet Size=4096"

        ' Connect to the database and fill a data table, including the 
        ' schema information that contains the CustomerID column 
        ' constraint.
        Dim adapter As New SqlDataAdapter(selectCommand, connectionString)
        Dim data As New DataTable()
        data.Locale = System.Globalization.CultureInfo.InvariantCulture
        adapter.Fill(data)
        adapter.FillSchema(data, SchemaType.Source)

        Return data

    End Function

    <STAThread()> _
    Shared Sub Main()
        Application.EnableVisualStyles()
        Application.Run(New Form1())
    End Sub

End Class

Compiling the Code

This example requires:

  • References to the System, System.Data, System.Windows.Forms, and System.XML assemblies.

.NET Framework Security

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.

See also